-
Improve dead code removal of
switch
statements (#3659)With this release, esbuild will now remove
switch
statements in branches when minifying if they are known to never be evaluated:// Original code if (true) foo(); else switch (bar) { case 1: baz(); break } // Old output (with --minify) if(1)foo();else switch(bar){case 1:} // New output (with --minify) foo();
-
Empty enums should behave like an object literal (#3657)
TypeScript allows you to create an empty enum and add properties to it at run time. While people usually use an empty object literal for this instead of a TypeScript enum, esbuild's enum transform didn't anticipate this use case and generated
undefined
instead of{}
for an empty enum. With this release, you can now use an empty enum to generate an empty object literal.// Original code enum Foo {} // Old output (with --loader=ts) var Foo = /* @__PURE__ */ ((Foo2) => { })(Foo || {}); // New output (with --loader=ts) var Foo = /* @__PURE__ */ ((Foo2) => { return Foo2; })(Foo || {});
-
Fix a bug with the CSS nesting transform (#3648)
This release fixes a bug with the CSS nesting transform for older browsers where the generated CSS could be incorrect if a selector list contained a pseudo element followed by another selector. The bug was caused by incorrectly mutating the parent rule's selector list when filtering out pseudo elements for the child rules:
/* Original code */ .foo { &:after, & .bar { color: red; } } /* Old output (with --supported:nesting=false) */ .foo .bar, .foo .bar { color: red; } /* New output (with --supported:nesting=false) */ .foo:after, .foo .bar { color: red; }
-
Constant folding for JavaScript inequality operators (#3645)
This release introduces constant folding for the
< > <= >=
operators. The minifier will now replace these operators withtrue
orfalse
when both sides are compile-time numeric or string constants:// Original code console.log(1 < 2, '🍕' > '🧀') // Old output (with --minify) console.log(1<2,"🍕">"🧀"); // New output (with --minify) console.log(!0,!1);
-
Better handling of
__proto__
edge cases (#3651)JavaScript object literal syntax contains a special case where a non-computed property with a key of
__proto__
sets the prototype of the object. This does not apply to computed properties or to properties that use the shorthand property syntax introduced in ES6. Previously esbuild didn't correctly preserve the "sets the prototype" status of properties inside an object literal, meaning a property that sets the prototype could accidentally be transformed into one that doesn't and vice versa. This has now been fixed:// Original code function foo(__proto__) { return { __proto__: __proto__ } // Note: sets the prototype } function bar(__proto__, proto) { { let __proto__ = proto return { __proto__ } // Note: doesn't set the prototype } } // Old output function foo(__proto__) { return { __proto__ }; // Note: no longer sets the prototype (WRONG) } function bar(__proto__, proto) { { let __proto__2 = proto; return { __proto__: __proto__2 }; // Note: now sets the prototype (WRONG) } } // New output function foo(__proto__) { return { __proto__: __proto__ }; // Note: sets the prototype (correct) } function bar(__proto__, proto) { { let __proto__2 = proto; return { ["__proto__"]: __proto__2 }; // Note: doesn't set the prototype (correct) } }
-
Fix cross-platform non-determinism with CSS color space transformations (#3650)
The Go compiler takes advantage of "fused multiply and add" (FMA) instructions on certain processors which do the operation
x*y + z
without intermediate rounding. This causes esbuild's CSS color space math to differ on different processors (currentlyppc64le
ands390x
), which breaks esbuild's guarantee of deterministic output. To avoid this, esbuild's color space math now inserts afloat64()
cast around every single math operation. This tells the Go compiler not to use the FMA optimization. -
Fix a crash when resolving a path from a directory that doesn't exist (#3634)
This release fixes a regression where esbuild could crash when resolving an absolute path if the source directory for the path resolution operation doesn't exist. While this situation doesn't normally come up, it could come up when running esbuild concurrently with another operation that mutates the file system as esbuild is doing a build (such as using
git
to switch branches). The underlying problem was a regression that was introduced in version 0.18.0.
This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild
in your package.json
file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.19.0
or ~0.19.0
. See npm's documentation about semver for more information.
This time there is only one breaking change, and it only matters for people using Deno. Deno tests that use esbuild will now fail unless you make the change described below.
-
Work around API deprecations in Deno 1.40.x (#3609, #3611)
Deno 1.40.0 was just released and introduced run-time warnings about certain APIs that esbuild uses. With this release, esbuild will work around these run-time warnings by using newer APIs if they are present and falling back to the original APIs otherwise. This should avoid the warnings without breaking compatibility with older versions of Deno.
Unfortunately, doing this introduces a breaking change. The newer child process APIs lack a way to synchronously terminate esbuild's child process, so calling
esbuild.stop()
from within a Deno test is no longer sufficient to prevent Deno from failing a test that uses esbuild's API (Deno fails tests that create a child process without killing it before the test ends). To work around this, esbuild'sstop()
function has been changed to return a promise, and you now have to changeesbuild.stop()
toawait esbuild.stop()
in all of your Deno tests. -
Reorder implicit file extensions within
node_modules
(#3341, #3608)In version 0.18.0, esbuild changed the behavior of implicit file extensions within
node_modules
directories (i.e. in published packages) to prefer.js
over.ts
even when the--resolve-extensions=
order prefers.ts
over.js
(which it does by default). However, doing that also accidentally made esbuild prefer.css
over.ts
, which caused problems for people that published packages containing both TypeScript and CSS in files with the same name.With this release, esbuild will reorder TypeScript file extensions immediately after the last JavaScript file extensions in the implicit file extension order instead of putting them at the end of the order. Specifically the default implicit file extension order is
.tsx,.ts,.jsx,.js,.css,.json
which used to become.jsx,.js,.css,.json,.tsx,.ts
innode_modules
directories. With this release it will now become.jsx,.js,.tsx,.ts,.css,.json
instead.Why even rewrite the implicit file extension order at all? One reason is because the
.js
file is more likely to behave correctly than the.ts
file. The behavior of the.ts
file may depend ontsconfig.json
and thetsconfig.json
file may not even be published, or may useextends
to refer to a basetsconfig.json
file that wasn't published. People can get into this situation when they forget to add all.ts
files to their.npmignore
file before publishing to npm. Picking.js
over.ts
helps make it more likely that resulting bundle will behave correctly.
-
The "preserve" JSX mode now preserves JSX text verbatim (#3605)
The JSX specification deliberately doesn't specify how JSX text is supposed to be interpreted and there is no canonical way to interpret JSX text. Two most popular interpretations are Babel and TypeScript. Yes they are different (esbuild deliberately follows TypeScript by the way).
Previously esbuild normalized text to the TypeScript interpretation when the "preserve" JSX mode is active. However, "preserve" should arguably reproduce the original JSX text verbatim so that whatever JSX transform runs after esbuild is free to interpret it however it wants. So with this release, esbuild will now pass JSX text through unmodified:
// Original code let el = <a href={'/'} title=''"'> some text {foo} more text </a> // Old output (with --loader=jsx --jsx=preserve) let el = <a href="/" title={`'"`}> {" some text"} {foo} {"more text "} </a>; // New output (with --loader=jsx --jsx=preserve) let el = <a href={"/"} title=''"'> some text {foo} more text </a>;
-
Allow JSX elements as JSX attribute values
JSX has an obscure feature where you can use JSX elements in attribute position without surrounding them with
{...}
. It looks like this:let el = <div data-ab=<><a/><b/></>/>;
I think I originally didn't implement it even though it's part of the JSX specification because it previously didn't work in TypeScript (and potentially also in Babel?). However, support for it was silently added in TypeScript 4.8 without me noticing and Babel has also since fixed their bugs regarding this feature. So I'm adding it to esbuild too now that I know it's widely supported.
Keep in mind that there is some ongoing discussion about removing this feature from JSX. I agree that the syntax seems out of place (it does away with the elegance of "JSX is basically just XML with
{...}
escapes" for something arguably harder to read, which doesn't seem like a good trade-off), but it's in the specification and TypeScript and Babel both implement it so I'm going to have esbuild implement it too. However, I reserve the right to remove it from esbuild if it's ever removed from the specification in the future. So use it with caution. -
Fix a bug with TypeScript type parsing (#3574)
This release fixes a bug with esbuild's TypeScript parser where a conditional type containing a union type that ends with an infer type that ends with a constraint could fail to parse. This was caused by the "don't parse a conditional type" flag not getting passed through the union type parser. Here's an example of valid TypeScript code that previously failed to parse correctly:
type InferUnion<T> = T extends { a: infer U extends number } | infer U extends number ? U : never
-
Fix TypeScript-specific class transform edge case (#3559)
The previous release introduced an optimization that avoided transforming
super()
in the class constructor for TypeScript code compiled withuseDefineForClassFields
set tofalse
if all class instance fields have no initializers. The rationale was that in this case, all class instance fields are omitted in the output so no changes to the constructor are needed. However, if all of this is the case and there are#private
instance fields with initializers, those private instance field initializers were still being moved into the constructor. This was problematic because they were being inserted before the call tosuper()
(sincesuper()
is now no longer transformed in that case). This release introduces an additional optimization that avoids moving the private instance field initializers into the constructor in this edge case, which generates smaller code, matches the TypeScript compiler's output more closely, and avoids this bug:// Original code class Foo extends Bar { #private = 1; public: any; constructor() { super(); } } // Old output (with esbuild v0.19.9) class Foo extends Bar { constructor() { super(); this.#private = 1; } #private; } // Old output (with esbuild v0.19.10) class Foo extends Bar { constructor() { this.#private = 1; super(); } #private; } // New output class Foo extends Bar { #private = 1; constructor() { super(); } }
-
Minifier: allow reording a primitive past a side-effect (#3568)
The minifier previously allowed reordering a side-effect past a primitive, but didn't handle the case of reordering a primitive past a side-effect. This additional case is now handled:
// Original code function f() { let x = false; let y = x; const boolean = y; let frag = $.template(`<p contenteditable="${boolean}">hello world</p>`); return frag; } // Old output (with --minify) function f(){const e=!1;return $.template(`<p contenteditable="${e}">hello world</p>`)} // New output (with --minify) function f(){return $.template('<p contenteditable="false">hello world</p>')}
-
Minifier: consider properties named using known
Symbol
instances to be side-effect free (#3561)Many things in JavaScript can have side effects including property accesses and ToString operations, so using a symbol such as
Symbol.iterator
as a computed property name is not obviously side-effect free. This release adds a special case for knownSymbol
instances so that they are considered side-effect free when used as property names. For example, this class declaration will now be considered side-effect free:class Foo { *[Symbol.iterator]() { } }
-
Provide the
stop()
API in node to exit esbuild's child process (#3558)You can now call
stop()
in esbuild's node API to exit esbuild's child process to reclaim the resources used. It only makes sense to do this for a long-lived node process when you know you will no longer be making any more esbuild API calls. It is not necessary to call this to allow node to exit, and it's advantageous to not call this in between calls to esbuild's API as sharing a single long-lived esbuild child process is more efficient than re-creating a new esbuild child process for every API call. This API call used to exist but was removed in version 0.9.0. This release adds it back due to a user request.
-
Fix glob imports in TypeScript files (#3319)
This release fixes a problem where bundling a TypeScript file containing a glob import could emit a call to a helper function that doesn't exist. The problem happened because esbuild's TypeScript transformation removes unused imports (which is required for correctness, as they may be type-only imports) and esbuild's glob import transformation wasn't correctly marking the imported helper function as used. This wasn't caught earlier because most of esbuild's glob import tests were written in JavaScript, not in TypeScript.
-
Fix
require()
glob imports with bundling disabled (#3546)Previously
require()
calls containing glob imports were incorrectly transformed when bundling was disabled. All glob imports should only be transformed when bundling is enabled. This bug has been fixed. -
Fix a panic when transforming optional chaining with
define
(#3551, #3554)This release fixes a case where esbuild could crash with a panic, which was triggered by using
define
to replace an expression containing an optional chain. Here is an example:// Original code console.log(process?.env.SHELL) // Old output (with --define:process.env={}) /* panic: Internal error (while parsing "<stdin>") */ // New output (with --define:process.env={}) var define_process_env_default = {}; console.log(define_process_env_default.SHELL);
This fix was contributed by @hi-ogawa.
-
Work around a bug in node's CommonJS export name detector (#3544)
The export names of a CommonJS module are dynamically-determined at run time because CommonJS exports are properties on a mutable object. But the export names of an ES module are statically-determined at module instantiation time by using
import
andexport
syntax and cannot be changed at run time.When you import a CommonJS module into an ES module in node, node scans over the source code to attempt to detect the set of export names that the CommonJS module will end up using. That statically-determined set of names is used as the set of names that the ES module is allowed to import at module instantiation time. However, this scan appears to have bugs (or at least, can cause false positives) because it doesn't appear to do any scope analysis. Node will incorrectly consider the module to export something even if the assignment is done to a local variable instead of to the module-level
exports
object. For example:// confuseNode.js exports.confuseNode = function(exports) { // If this local is called "exports", node incorrectly // thinks this file has an export called "notAnExport". exports.notAnExport = function() { }; };
You can see that node incorrectly thinks the file
confuseNode.js
has an export callednotAnExport
when that file is loaded in an ES module context:$ node -e 'import("./confuseNode.js").then(console.log)' [Module: null prototype] { confuseNode: [Function (anonymous)], default: { confuseNode: [Function (anonymous)] }, notAnExport: undefined }
To avoid this, esbuild will now rename local variables that use the names
exports
andmodule
when generating CommonJS output for thenode
platform. -
Fix the return value of esbuild's
super()
shim (#3538)Some people write
constructor
methods that use the return value ofsuper()
instead of usingthis
. This isn't too common because TypeScript doesn't let you do that but it can come up when writing JavaScript. Previously esbuild's class lowering transform incorrectly transformed the return value ofsuper()
intoundefined
. With this release, the return value ofsuper()
will now bethis
instead:// Original code class Foo extends Object { field constructor() { console.log(typeof super()) } } new Foo // Old output (with --target=es6) class Foo extends Object { constructor() { var __super = (...args) => { super(...args); __publicField(this, "field"); }; console.log(typeof __super()); } } new Foo(); // New output (with --target=es6) class Foo extends Object { constructor() { var __super = (...args) => { super(...args); __publicField(this, "field"); return this; }; console.log(typeof __super()); } } new Foo();
-
Terminate the Go GC when esbuild's
stop()
API is called (#3552)If you use esbuild with WebAssembly and pass the
worker: false
flag toesbuild.initialize()
, then esbuild will run the WebAssembly module on the main thread. If you do this within a Deno test and that test callsesbuild.stop()
to clean up esbuild's resources, Deno may complain that asetTimeout()
call lasted past the end of the test. This happens when the Go is in the middle of a garbage collection pass and has scheduled additional ongoing garbage collection work. Normally callingesbuild.stop()
will terminate the web worker that the WebAssembly module runs in, which will terminate the Go GC, but that doesn't happen if you disable the web worker withworker: false
.With this release, esbuild will now attempt to terminate the Go GC in this edge case by calling
clearTimeout()
on these pending timeouts. -
Apply
/* @__NO_SIDE_EFFECTS__ */
on tagged template literals (#3511)Tagged template literals that reference functions annotated with a
@__NO_SIDE_EFFECTS__
comment are now able to be removed via tree-shaking if the result is unused. This is a convention from Rollup. Here is an example:// Original code const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b }) html`<a>remove</a>` x = html`<b>keep</b>` // Old output (with --tree-shaking=true) const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b }); html`<a>remove</a>`; x = html`<b>keep</b>`; // New output (with --tree-shaking=true) const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b }); x = html`<b>keep</b>`;
Note that this feature currently only works within a single file, so it's not especially useful. This feature does not yet work across separate files. I still recommend using
@__PURE__
annotations instead of this feature, as they have wider tooling support. The drawback of course is that@__PURE__
annotations need to be added at each call site, not at the declaration, and for non-call expressions such as template literals you need to wrap the expression in an IIFE (immediately-invoked function expression) to create a call expression to apply the@__PURE__
annotation to. -
Publish builds for IBM AIX PowerPC 64-bit (#3549)
This release publishes a binary executable to npm for IBM AIX PowerPC 64-bit, which means that in theory esbuild can now be installed in that environment with
npm install esbuild
. This hasn't actually been tested yet. If you have access to such a system, it would be helpful to confirm whether or not doing this actually works.
-
Add support for transforming new CSS gradient syntax for older browsers
The specification called CSS Images Module Level 4 introduces new CSS gradient syntax for customizing how the browser interpolates colors in between color stops. You can now control the color space that the interpolation happens in as well as (for "polar" color spaces) control whether hue angle interpolation happens clockwise or counterclockwise. You can read more about this in Mozilla's blog post about new CSS gradient features.
With this release, esbuild will now automatically transform this syntax for older browsers in the
target
list. For example, here's a gradient that should appear as a rainbow in a browser that supports this new syntax:/* Original code */ .rainbow-gradient { width: 100px; height: 100px; background: linear-gradient(in hsl longer hue, #7ff, #77f); } /* New output (with --target=chrome99) */ .rainbow-gradient { width: 100px; height: 100px; background: linear-gradient( #77ffff, #77ffaa 12.5%, #77ff80 18.75%, #84ff77 21.88%, #99ff77 25%, #eeff77 37.5%, #fffb77 40.62%, #ffe577 43.75%, #ffbb77 50%, #ff9077 56.25%, #ff7b77 59.38%, #ff7788 62.5%, #ff77dd 75%, #ff77f2 78.12%, #f777ff 81.25%, #cc77ff 87.5%, #7777ff); }
You can now use this syntax in your CSS source code and esbuild will automatically convert it to an equivalent gradient for older browsers. In addition, esbuild will now also transform "double position" and "transition hint" syntax for older browsers as appropriate:
/* Original code */ .stripes { width: 100px; height: 100px; background: linear-gradient(#e65 33%, #ff2 33% 67%, #99e 67%); } .glow { width: 100px; height: 100px; background: radial-gradient(white 10%, 20%, black); } /* New output (with --target=chrome33) */ .stripes { width: 100px; height: 100px; background: linear-gradient( #e65 33%, #ff2 33%, #ff2 67%, #99e 67%); } .glow { width: 100px; height: 100px; background: radial-gradient( #ffffff 10%, #aaaaaa 12.81%, #959595 15.62%, #7b7b7b 21.25%, #5a5a5a 32.5%, #444444 43.75%, #323232 55%, #161616 77.5%, #000000); }
You can see visual examples of these new syntax features by looking at esbuild's gradient transformation tests.
If necessary, esbuild will construct a new gradient that approximates the original gradient by recursively splitting the interval in between color stops until the approximation error is within a small threshold. That is why the above output CSS contains many more color stops than the input CSS.
Note that esbuild deliberately replaces the original gradient with the approximation instead of inserting the approximation before the original gradient as a fallback. The latest version of Firefox has multiple gradient rendering bugs (including incorrect interpolation of partially-transparent colors and interpolating non-sRGB colors using the incorrect color space). If esbuild didn't replace the original gradient, then Firefox would use the original gradient instead of the fallback the appearance would be incorrect in Firefox. In other words, the latest version of Firefox supports modern gradient syntax but interprets it incorrectly.
-
Add support for
color()
,lab()
,lch()
,oklab()
,oklch()
, andhwb()
in CSSCSS has recently added lots of new ways of specifying colors. You can read more about this in Chrome's blog post about CSS color spaces.
This release adds support for minifying colors that use the
color()
,lab()
,lch()
,oklab()
,oklch()
, orhwb()
syntax and/or transforming these colors for browsers that don't support it yet:/* Original code */ div { color: hwb(90deg 20% 40%); background: color(display-p3 1 0 0); } /* New output (with --target=chrome99) */ div { color: #669933; background: #ff0f0e; background: color(display-p3 1 0 0); }
As you can see, colors outside of the sRGB color space such as
color(display-p3 1 0 0)
are mapped back into the sRGB gamut and inserted as a fallback for browsers that don't support the new color syntax. -
Allow empty type parameter lists in certain cases (#3512)
TypeScript allows interface declarations and type aliases to have empty type parameter lists. Previously esbuild didn't handle this edge case but with this release, esbuild will now parse this syntax:
interface Foo<> {} type Bar<> = {}
This fix was contributed by @magic-akari.
-
Add a treemap chart to esbuild's bundle analyzer (#2848)
The bundler analyzer on esbuild's website (https://esbuild.github.io/analyze/) now has a treemap chart type in addition to the two existing chart types (sunburst and flame). This should be more familiar for people coming from other similar tools, as well as make better use of large screens.
-
Allow decorators after the
export
keyword (#104)Previously esbuild's decorator parser followed the original behavior of TypeScript's experimental decorators feature, which only allowed decorators to come before the
export
keyword. However, the upcoming JavaScript decorators feature also allows decorators to come after theexport
keyword. And with TypeScript 5.0, TypeScript now also allows experimental decorators to come after theexport
keyword too. So esbuild now allows this as well:// This old syntax has always been permitted: @decorator export class Foo {} @decorator export default class Foo {} // This new syntax is now permitted too: export @decorator class Foo {} export default @decorator class Foo {}
In addition, esbuild's decorator parser has been rewritten to fix several subtle and likely unimportant edge cases with esbuild's parsing of exports and decorators in TypeScript (e.g. TypeScript apparently does automatic semicolon insertion after
interface
andexport interface
but not afterexport default interface
). -
Pretty-print decorators using the same whitespace as the original
When printing code containing decorators, esbuild will now try to respect whether the original code contained newlines after the decorator or not. This can make generated code containing many decorators much more compact to read:
// Original code class Foo { @a @b @c abc @x @y @z xyz } // Old output class Foo { @a @b @c abc; @x @y @z xyz; } // New output class Foo { @a @b @c abc; @x @y @z xyz; }
-
Add support for bundling code that uses import attributes (#3384)
JavaScript is gaining new syntax for associating a map of string key-value pairs with individual ESM imports. The proposal is still a work in progress and is still undergoing significant changes before being finalized. However, the first iteration has already been shipping in Chromium-based browsers for a while, and the second iteration has landed in V8 and is now shipping in node, so it makes sense for esbuild to support it. Here are the two major iterations of this proposal (so far):
-
Import assertions (deprecated, will not be standardized)
- Uses the
assert
keyword - Does not affect module resolution
- Causes an error if the assertion fails
- Shipping in Chrome 91+ (and in esbuild 0.11.22+)
- Uses the
-
Import attributes (currently set to become standardized)
- Uses the
with
keyword - Affects module resolution
- Unknown attributes cause an error
- Shipping in node 21+
- Uses the
You can already use esbuild to bundle code that uses import assertions (the first iteration). However, this feature is mostly useless for bundlers because import assertions are not allowed to affect module resolution. It's basically only useful as an annotation on external imports, which esbuild will then preserve in the output for use in a browser (which would otherwise refuse to load certain imports).
With this release, esbuild now supports bundling code that uses import attributes (the second iteration). This is much more useful for bundlers because they are allowed to affect module resolution, which means the key-value pairs can be provided to plugins. Here's an example, which uses esbuild's built-in support for the upcoming JSON module standard:
// On static imports import foo from './package.json' with { type: 'json' } console.log(foo) // On dynamic imports const bar = await import('./package.json', { with: { type: 'json' } }) console.log(bar)
One important consequence of the change in semantics between import assertions and import attributes is that two imports with identical paths but different import attributes are now considered to be different modules. This is because the import attributes are provided to the loader, which might then use those attributes during loading. For example, you could imagine an image loader that produces an image of a different size depending on the import attributes.
Import attributes are now reported in the metafile and are now provided to on-load plugins as a map in the
with
property. For example, here's an esbuild plugin that turns all imports with atype
import attribute equal to'cheese'
into a module that exports the cheese emoji:const cheesePlugin = { name: 'cheese', setup(build) { build.onLoad({ filter: /.*/ }, args => { if (args.with.type === 'cheese') return { contents: `export default "🧀"`, } }) } } require('esbuild').build({ bundle: true, write: false, stdin: { contents: ` import foo from 'data:text/javascript,' with { type: 'cheese' } console.log(foo) `, }, plugins: [cheesePlugin], }).then(result => { const code = new Function(result.outputFiles[0].text) code() })
Warning: It's possible that the second iteration of this feature may change significantly again even though it's already shipping in real JavaScript VMs (since it has already happened once before). In that case, esbuild may end up adjusting its implementation to match the eventual standard behavior. So keep in mind that by using this, you are using an unstable upcoming JavaScript feature that may undergo breaking changes in the future.
-
-
Adjust TypeScript experimental decorator behavior (#3230, #3326, #3394)
With this release, esbuild will now allow TypeScript experimental decorators to access both static class properties and
#private
class names. For example:const check = <T,>(a: T, b: T): PropertyDecorator => () => console.log(a === b) async function test() { class Foo { static #foo = 1 static bar = 1 + Foo.#foo @check(Foo.#foo, 1) a: any @check(Foo.bar, await Promise.resolve(2)) b: any } } test().then(() => console.log('pass'))
This will now print
true true pass
when compiled by esbuild. Previously esbuild evaluated TypeScript decorators outside of the class body, so it didn't allow decorators to accessFoo
or#foo
. Now esbuild does something different, although it's hard to concisely explain exactly what esbuild is doing now (see the background section below for more information).Note that TypeScript's experimental decorator support is currently buggy: TypeScript's compiler passes this test if only the first
@check
is present or if only the second@check
is present, but TypeScript's compiler fails this test if both checks are present together. I haven't changed esbuild to match TypeScript's behavior exactly here because I'm waiting for TypeScript to fix these bugs instead.Some background: TypeScript experimental decorators don't have consistent semantics regarding the context that the decorators are evaluated in. For example, TypeScript will let you use
await
within a decorator, which implies that the decorator runs outside the class body (sinceawait
isn't supported inside a class body), but TypeScript will also let you use#private
names, which implies that the decorator runs inside the class body (since#private
names are only supported inside a class body). The value ofthis
in a decorator is also buggy (the run-time value ofthis
changes if any decorator in the class uses a#private
name but the type ofthis
doesn't change, leading to the type checker no longer matching reality). These inconsistent semantics make it hard for esbuild to implement this feature as decorator evaluation happens in some superposition of both inside and outside the class body that is particular to the internal implementation details of the TypeScript compiler. -
Forbid
--keep-names
when targeting old browsers (#3477)The
--keep-names
setting needs to be able to assign to thename
property on functions and classes. However, before ES6 this property was non-configurable, and attempting to assign to it would throw an error. So with this release, esbuild will no longer allow you to enable this setting while also targeting a really old browser.
-
Fix a constant folding bug with bigint equality
This release fixes a bug where esbuild incorrectly checked for bigint equality by checking the equality of the bigint literal text. This is correct if the bigint doesn't have a radix because bigint literals without a radix are always in canonical form (since leading zeros are not allowed). However, this is incorrect if the bigint has a radix (e.g.
0x123n
) because the canonical form is not enforced when a radix is present.// Original code console.log(!!0n, !!1n, 123n === 123n) console.log(!!0x0n, !!0x1n, 123n === 0x7Bn) // Old output console.log(false, true, true); console.log(true, true, false); // New output console.log(false, true, true); console.log(!!0x0n, !!0x1n, 123n === 0x7Bn);
-
Add some improvements to the JavaScript minifier
This release adds more cases to the JavaScript minifier, including support for inlining
String.fromCharCode
andString.prototype.charCodeAt
when possible:// Original code document.onkeydown = e => e.keyCode === 'A'.charCodeAt(0) && console.log(String.fromCharCode(55358, 56768)) // Old output (with --minify) document.onkeydown=o=>o.keyCode==="A".charCodeAt(0)&&console.log(String.fromCharCode(55358,56768)); // New output (with --minify) document.onkeydown=o=>o.keyCode===65&&console.log("🧀");
In addition, immediately-invoked function expressions (IIFEs) that return a single expression are now inlined when minifying. This makes it possible to use IIFEs in combination with
@__PURE__
annotations to annotate arbitrary expressions as side-effect free without the IIFE wrapper impacting code size. For example:// Original code const sideEffectFreeOffset = /* @__PURE__ */ (() => computeSomething())() use(sideEffectFreeOffset) // Old output (with --minify) const e=(()=>computeSomething())();use(e); // New output (with --minify) const e=computeSomething();use(e);
-
Automatically prefix the
mask-composite
CSS property for WebKit (#3493)The
mask-composite
property will now be prefixed as-webkit-mask-composite
for older WebKit-based browsers. In addition to prefixing the property name, handling older browsers also requires rewriting the values since WebKit uses non-standard names for the mask composite modes:/* Original code */ div { mask-composite: add, subtract, intersect, exclude; } /* New output (with --target=chrome100) */ div { -webkit-mask-composite: source-over, source-out, source-in, xor; mask-composite: add, subtract, intersect, exclude; }
-
Avoid referencing
this
from JSX elements in derived class constructors (#3454)When you enable
--jsx=automatic
and--jsx-dev
, the JSX transform is supposed to insertthis
as the last argument to thejsxDEV
function. I'm not sure exactly why this is and I can't find any specification for it, but in any case this causes the generated code to crash when you use a JSX element in a derived class constructor before the call tosuper()
asthis
is not allowed to be accessed at that point. For example// Original code class ChildComponent extends ParentComponent { constructor() { super(<div />) } } // Problematic output (with --loader=jsx --jsx=automatic --jsx-dev) import { jsxDEV } from "react/jsx-dev-runtime"; class ChildComponent extends ParentComponent { constructor() { super(/* @__PURE__ */ jsxDEV("div", {}, void 0, false, { fileName: "<stdin>", lineNumber: 3, columnNumber: 15 }, this)); // The reference to "this" crashes here } }
The TypeScript compiler doesn't handle this at all while the Babel compiler just omits
this
for the entire constructor (even after the call tosuper()
). There seems to be no specification so I can't be sure that this change doesn't break anything important. But given that Babel is pretty loose with this and TypeScript doesn't handle this at all, I'm guessing this value isn't too important. React's blog post seems to indicate that this value was intended to be used for a React-specific migration warning at some point, so it could even be that this value is irrelevant now. Anyway the crash in this case should now be fixed. -
Allow package subpath imports to map to node built-ins (#3485)
You are now able to use a subpath import in your package to resolve to a node built-in module. For example, with a
package.json
file like this:{ "type": "module", "imports": { "#stream": { "node": "stream", "default": "./stub.js" } } }
You can now import from node's
stream
module like this:import * as stream from '#stream'; console.log(Object.keys(stream));
This will import from node's
stream
module when the platform isnode
and from./stub.js
otherwise. -
No longer throw an error when a
Symbol
is missing (#3453)Certain JavaScript syntax features use special properties on the global
Symbol
object. For example, the asynchronous iteration syntax usesSymbol.asyncIterator
. Previously esbuild's generated code for older browsers required this symbol to be polyfilled. However, starting with this release esbuild will useSymbol.for()
to construct these symbols if they are missing instead of throwing an error about a missing polyfill. This means your code no longer needs to include a polyfill for missing symbols as long as your code also usesSymbol.for()
for missing symbols. -
Parse upcoming changes to TypeScript syntax (#3490, #3491)
With this release, you can now use
from
as the name of a default type-only import in TypeScript code, as well asof
as the name of anawait using
loop iteration variable:import type from from 'from' for (await using of of of) ;
This matches similar changes in the TypeScript compiler (#56376 and #55555) which will start allowing this syntax in an upcoming version of TypeScript. Please never actually write code like this.
The type-only import syntax change was contributed by @magic-akari.
-
Fix a regression in 0.19.0 regarding
paths
intsconfig.json
(#3354)The fix in esbuild version 0.19.0 to process
tsconfig.json
aliases before the--packages=external
setting unintentionally broke an edge case in esbuild's handling of certaintsconfig.json
aliases where there are multiple files with the same name in different directories. This release adjusts esbuild's behavior for this edge case so that it passes while still processing aliases before--packages=external
. Please read the linked issue for more details. -
Fix a CSS
font
property minification bug (#3452)This release fixes a bug where esbuild's CSS minifier didn't insert a space between the font size and the font family in the
font
CSS shorthand property in the edge case where the original source code didn't already have a space and the leading string token was shortened to an identifier:/* Original code */ .foo { font: 16px"Menlo"; } /* Old output (with --minify) */ .foo{font:16pxMenlo} /* New output (with --minify) */ .foo{font:16px Menlo}
-
Fix bundling CSS with asset names containing spaces (#3410)
Assets referenced via CSS
url()
tokens may cause esbuild to generate invalid output when bundling if the file name contains spaces (e.g.url(image 2.png)
). With this release, esbuild will now quote all bundled asset references inurl()
tokens to avoid this problem. This only affects assets loaded using thefile
andcopy
loaders. -
Fix invalid CSS
url()
tokens in@import
rules (#3426)In the future, CSS
url()
tokens may contain additional stuff after the URL. This is irrelevant today as no CSS specification does this. But esbuild previously had a bug where using these tokens in an@import
rule resulted in malformed output. This bug has been fixed. -
Fix
browser
+false
+type: module
inpackage.json
(#3367)The
browser
field inpackage.json
allows you to map a file tofalse
to have it be treated as an empty file when bundling for the browser. However, ifpackage.json
contains"type": "module"
then all.js
files will be considered ESM, not CommonJS. Importing a named import from an empty CommonJS file gives you undefined, but importing a named export from an empty ESM file is a build error. This release changes esbuild's interpretation of these files mapped tofalse
in this situation from ESM to CommonJS to avoid generating build errors for named imports. -
Fix a bug in top-level await error reporting (#3400)
Using
require()
on a file that contains top-level await is not allowed becauserequire()
must return synchronously and top-level await makes that impossible. You will get a build error if you try to bundle code that does this with esbuild. This release fixes a bug in esbuild's error reporting code for complex cases of this situation involving multiple levels of imports to get to the module containing the top-level await. -
Update to Unicode 15.1.0
The character tables that determine which characters form valid JavaScript identifiers have been updated from Unicode version 15.0.0 to the newly-released Unicode version 15.1.0. I'm not putting an example in the release notes because all of the new characters will likely just show up as little squares since fonts haven't been updated yet. But you can read https://www.unicode.org/versions/Unicode15.1.0/#Summary for more information about the changes.
This upgrade was contributed by @JLHwung.
-
Fix printing of JavaScript decorators in tricky cases (#3396)
This release fixes some bugs where esbuild's pretty-printing of JavaScript decorators could incorrectly produced code with a syntax error. The problem happened because esbuild sometimes substitutes identifiers for other expressions in the pretty-printer itself, but the decision about whether to wrap the expression or not didn't account for this. Here are some examples:
// Original code import { constant } from './constants.js' import { imported } from 'external' import { undef } from './empty.js' class Foo { @constant() @imported() @undef() foo } // Old output (with --bundle --format=cjs --packages=external --minify-syntax) var import_external = require("external"); var Foo = class { @123() @(0, import_external.imported)() @(void 0)() foo; }; // New output (with --bundle --format=cjs --packages=external --minify-syntax) var import_external = require("external"); var Foo = class { @(123()) @((0, import_external.imported)()) @((void 0)()) foo; };
-
Allow pre-release versions to be passed to
target
(#3388)People want to be able to pass version numbers for unreleased versions of node (which have extra stuff after the version numbers) to esbuild's
target
setting and have esbuild do something reasonable with them. These version strings are of course not present in esbuild's internal feature compatibility table because an unreleased version has not been released yet (by definition). With this release, esbuild will now attempt to accept these version strings passed totarget
and do something reasonable with them.
-
Fix
list-style-type
with thelocal-css
loader (#3325)The
local-css
loader incorrectly treated all identifiers provided tolist-style-type
as a custom local identifier. That included identifiers such asnone
which have special meaning in CSS, and which should not be treated as custom local identifiers. This release fixes this bug:/* Original code */ ul { list-style-type: none } /* Old output (with --loader=local-css) */ ul { list-style-type: stdin_none; } /* New output (with --loader=local-css) */ ul { list-style-type: none; }
Note that this bug only affected code using the
local-css
loader. It did not affect code using thecss
loader. -
Avoid inserting temporary variables before
use strict
(#3322)This release fixes a bug where esbuild could incorrectly insert automatically-generated temporary variables before
use strict
directives:// Original code function foo() { 'use strict' a.b?.c() } // Old output (with --target=es6) function foo() { var _a; "use strict"; (_a = a.b) == null ? void 0 : _a.c(); } // New output (with --target=es6) function foo() { "use strict"; var _a; (_a = a.b) == null ? void 0 : _a.c(); }
-
Adjust TypeScript
enum
output to better approximatetsc
(#3329)TypeScript enum values can be either number literals or string literals. Numbers create a bidirectional mapping between the name and the value but strings only create a unidirectional mapping from the name to the value. When the enum value is neither a number literal nor a string literal, TypeScript and esbuild both default to treating it as a number:
// Original TypeScript code declare const foo: any enum Foo { NUMBER = 1, STRING = 'a', OTHER = foo, } // Compiled JavaScript code (from "tsc") var Foo; (function (Foo) { Foo[Foo["NUMBER"] = 1] = "NUMBER"; Foo["STRING"] = "a"; Foo[Foo["OTHER"] = foo] = "OTHER"; })(Foo || (Foo = {}));
However, TypeScript does constant folding slightly differently than esbuild. For example, it may consider template literals to be string literals in some cases:
// Original TypeScript code declare const foo = 'foo' enum Foo { PRESENT = `${foo}`, MISSING = `${bar}`, } // Compiled JavaScript code (from "tsc") var Foo; (function (Foo) { Foo["PRESENT"] = "foo"; Foo[Foo["MISSING"] = `${bar}`] = "MISSING"; })(Foo || (Foo = {}));
The template literal initializer for
PRESENT
is treated as a string while the template literal initializer forMISSING
is treated as a number. Previously esbuild treated both of these cases as a number but starting with this release, esbuild will now treat both of these cases as a string. This doesn't exactly match the behavior oftsc
but in the case where the behavior divergestsc
reports a compile error, so this seems like acceptible behavior for esbuild. Note that handling these cases completely correctly would require esbuild to parse type declarations (see thedeclare
keyword), which esbuild deliberately doesn't do. -
Ignore case in CSS in more places (#3316)
This release makes esbuild's CSS support more case-agnostic, which better matches how browsers work. For example:
/* Original code */ @KeyFrames Foo { From { OpaCity: 0 } To { OpaCity: 1 } } body { CoLoR: YeLLoW } /* Old output (with --minify) */ @KeyFrames Foo{From {OpaCity: 0} To {OpaCity: 1}}body{CoLoR:YeLLoW} /* New output (with --minify) */ @KeyFrames Foo{0%{OpaCity:0}To{OpaCity:1}}body{CoLoR:#ff0}
Please never actually write code like this.
-
Improve the error message for
null
entries inexports
(#3377)Package authors can disable package export paths with the
exports
map inpackage.json
. With this release, esbuild now has a clearer error message that points to thenull
token inpackage.json
itself instead of to the surrounding context. Here is an example of the new error message:✘ [ERROR] Could not resolve "msw/browser" lib/msw-config.ts:2:28: 2 │ import { setupWorker } from 'msw/browser'; ╵ ~~~~~~~~~~~~~ The path "./browser" cannot be imported from package "msw" because it was explicitly disabled by the package author here: node_modules/msw/package.json:17:14: 17 │ "node": null, ╵ ~~~~ You can mark the path "msw/browser" as external to exclude it from the bundle, which will remove this error and leave the unresolved path in the bundle.
-
Parse and print the
with
keyword inimport
statementsJavaScript was going to have a feature called "import assertions" that adds an
assert
keyword toimport
statements. It looked like this:import stuff from './stuff.json' assert { type: 'json' }
The feature provided a way to assert that the imported file is of a certain type (but was not allowed to affect how the import is interpreted, even though that's how everyone expected it to behave). The feature was fully specified and then actually implemented and shipped in Chrome before the people behind the feature realized that they should allow it to affect how the import is interpreted after all. So import assertions are no longer going to be added to the language.
Instead, the current proposal is to add a feature called "import attributes" instead that adds a
with
keyword to import statements. It looks like this:import stuff from './stuff.json' with { type: 'json' }
This feature provides a way to affect how the import is interpreted. With this release, esbuild now has preliminary support for parsing and printing this new
with
keyword. Thewith
keyword is not yet interpreted by esbuild, however, so bundling code with it will generate a build error. All this release does is allow you to use esbuild to process code containing it (such as removing types from TypeScript code). Note that this syntax is not yet a part of JavaScript and may be removed or altered in the future if the specification changes (which it already has once, as described above). If that happens, esbuild reserves the right to remove or alter its support for this syntax too.
-
Update how CSS nesting is parsed again
CSS nesting syntax has been changed again, and esbuild has been updated to match. Type selectors may now be used with CSS nesting:
.foo { div { color: red; } }
Previously this was disallowed in the CSS specification because it's ambiguous whether an identifier is a declaration or a nested rule starting with a type selector without requiring unbounded lookahead in the parser. It has now been allowed because the CSS working group has decided that requiring unbounded lookahead is acceptable after all.
Note that this change means esbuild no longer considers any existing browser to support CSS nesting since none of the existing browsers support this new syntax. CSS nesting will now always be transformed when targeting a browser. This situation will change in the future as browsers add support for this new syntax.
-
Fix a scope-related bug with
--drop-labels=
(#3311)The recently-released
--drop-labels=
feature previously had a bug where esbuild's internal scope stack wasn't being restored properly when a statement with a label was dropped. This could manifest as a tree-shaking issue, although it's possible that this could have also been causing other subtle problems too. The bug has been fixed in this release. -
Make renamed CSS names unique across entry points (#3295)
Previously esbuild's generated names for local names in CSS were only unique within a given entry point (or across all entry points when code splitting was enabled). That meant that building multiple entry points with esbuild could result in local names being renamed to the same identifier even when those entry points were built simultaneously within a single esbuild API call. This problem was especially likely to happen with minification enabled. With this release, esbuild will now avoid renaming local names from two separate entry points to the same name if those entry points were built with a single esbuild API call, even when code splitting is disabled.
-
Fix CSS ordering bug with
@layer
before@import
CSS lets you put
@layer
rules before@import
rules to define the order of layers in a stylesheet. Previously esbuild's CSS bundler incorrectly ordered these after the imported files because before the introduction of cascade layers to CSS, imported files could be bundled by removing the@import
rules and then joining files together in the right order. But with@layer
, CSS files may now need to be split apart into multiple pieces in the bundle. For example:/* Original code */ @layer start; @import "data:text/css,@layer inner.start;"; @import "data:text/css,@layer inner.end;"; @layer end; /* Old output (with --bundle) */ @layer inner.start; @layer inner.end; @layer start; @layer end; /* New output (with --bundle) */ @layer start; @layer inner.start; @layer inner.end; @layer end;
-
Unwrap nested duplicate
@media
rules (#3226)With this release, esbuild's CSS minifier will now automatically unwrap duplicate nested
@media
rules:/* Original code */ @media (min-width: 1024px) { .foo { color: red } @media (min-width: 1024px) { .bar { color: blue } } } /* Old output (with --minify) */ @media (min-width: 1024px){.foo{color:red}@media (min-width: 1024px){.bar{color:#00f}}} /* New output (with --minify) */ @media (min-width: 1024px){.foo{color:red}.bar{color:#00f}}
These rules are unlikely to be authored manually but may result from using frameworks such as Tailwind to generate CSS.
-
Fix a regression with
baseURL
intsconfig.json
(#3307)The previous release moved
tsconfig.json
path resolution before--packages=external
checks to allow thepaths
field intsconfig.json
to avoid a package being marked as external. However, that reordering accidentally broke the behavior of thebaseURL
field fromtsconfig.json
. This release moves these path resolution rules around again in an attempt to allow both of these cases to work. -
Parse TypeScript type arguments for JavaScript decorators (#3308)
When parsing JavaScript decorators in TypeScript (i.e. with
experimentalDecorators
disabled), esbuild previously didn't parse type arguments. Type arguments will now be parsed starting with this release. For example:@foo<number> @bar<number, string>() class Foo {}
-
Fix glob patterns matching extra stuff at the end (#3306)
Previously glob patterns such as
./*.js
would incorrectly behave like./*.js*
during path matching (also matching.js.map
files, for example). This was never intentional behavior, and has now been fixed. -
Change the permissions of esbuild's generated output files (#3285)
This release changes the permissions of the output files that esbuild generates to align with the default behavior of node's
fs.writeFileSync
function. Since most tools written in JavaScript usefs.writeFileSync
, this should make esbuild more consistent with how other JavaScript build tools behave.The full Unix-y details: Unix permissions use three-digit octal notation where the three digits mean "user, group, other" in that order. Within a digit, 4 means "read" and 2 means "write" and 1 means "execute". So 6 == 4 + 2 == read + write. Previously esbuild uses 0644 permissions (the leading 0 means octal notation) but the permissions for
fs.writeFileSync
defaults to 0666, so esbuild will now use 0666 permissions. This does not necessarily mean that the files esbuild generates will end up having 0666 permissions, however, as there is another Unix feature called "umask" where the operating system masks out some of these bits. If your umask is set to 0022 then the generated files will have 0644 permissions, and if your umask is set to 0002 then the generated files will have 0664 permissions. -
Fix a subtle CSS ordering issue with
@import
and@layer
With this release, esbuild may now introduce additional
@layer
rules when bundling CSS to better preserve the layer ordering of the input code. Here's an example of an edge case where this matters:/* entry.css */ @import "a.css"; @import "b.css"; @import "a.css";
/* a.css */ @layer a { body { background: red; } }
/* b.css */ @layer b { body { background: green; } }
This CSS should set the body background to
green
, which is what happens in the browser. Previously esbuild generated the following output which incorrectly sets the body background tored
:/* b.css */ @layer b { body { background: green; } } /* a.css */ @layer a { body { background: red; } }
This difference in behavior is because the browser evaluates
a.css
+b.css
+a.css
(in CSS, each@import
is replaced with a copy of the imported file) while esbuild was only writing outb.css
+a.css
. The first copy ofa.css
wasn't being written out by esbuild for two reasons: 1) bundlers care about code size and try to avoid emitting duplicate CSS and 2) when there are multiple copies of a CSS file, normally only the last copy matters since the last declaration with equal specificity wins in CSS.However,
@layer
was recently added to CSS and for@layer
the first copy matters because layers are ordered using their first location in source code order. This introduction of@layer
means esbuild needs to change its bundling algorithm. An easy solution would be for esbuild to write outa.css
twice, but that would be inefficient. So what I'm going to try to have esbuild do with this release is to write out an abbreviated form of the first copy of a CSS file that only includes the@layer
information, and then still only write out the full CSS file once for the last copy. So esbuild's output for this edge case now looks like this:/* a.css */ @layer a; /* b.css */ @layer b { body { background: green; } } /* a.css */ @layer a { body { background: red; } }
The behavior of the bundled CSS now matches the behavior of the unbundled CSS. You may be wondering why esbuild doesn't just write out
a.css
first followed byb.css
. That would work in this case but it doesn't work in general because for any rules outside of a@layer
rule, the last copy should still win instead of the first copy. -
Fix a bug with esbuild's TypeScript type definitions (#3299)
This release fixes a copy/paste error with the TypeScript type definitions for esbuild's JS API:
export interface TsconfigRaw { compilerOptions?: { - baseUrl?: boolean + baseUrl?: string ... } }
This fix was contributed by @privatenumber.
This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild
in your package.json
file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.18.0
or ~0.18.0
. See npm's documentation about semver for more information.
-
Handle import paths containing wildcards (#56, #700, #875, #976, #2221, #2515)
This release introduces wildcards in import paths in two places:
-
Entry points
You can now pass a string containing glob-style wildcards such as
./src/*.ts
as an entry point and esbuild will search the file system for files that match the pattern. This can be used to easily pass esbuild all files with a certain extension on the command line in a cross-platform way. Previously you had to rely on the shell to perform glob expansion, but that is obviously shell-dependent and didn't work at all on Windows. Note that to use this feature on the command line you will have to quote the pattern so it's passed verbatim to esbuild without any expansion by the shell. Here's an example:esbuild --minify "./src/*.ts" --outdir=out
Specifically the
*
character will match any character except for the/
character, and the/**/
character sequence will match a path separator followed by zero or more path elements. Other wildcard operators found in glob patterns such as?
and[...]
are not supported. -
Run-time import paths
Import paths that are evaluated at run-time can now be bundled in certain limited situations. The import path expression must be a form of string concatenation and must start with either
./
or../
. Each non-string expression in the string concatenation chain becomes a wildcard. The*
wildcard is chosen unless the previous character is a/
, in which case the/**/*
character sequence is used. Some examples:// These two forms are equivalent const json1 = await import('./data/' + kind + '.json') const json2 = await import(`./data/${kind}.json`)
This feature works with
require(...)
andimport(...)
because these can all accept run-time expressions. It does not work withimport
andexport
statements because these cannot accept run-time expressions. If you want to prevent esbuild from trying to bundle these imports, you should move the string concatenation expression outside of therequire(...)
orimport(...)
. For example:// This will be bundled const json1 = await import('./data/' + kind + '.json') // This will not be bundled const path = './data/' + kind + '.json' const json2 = await import(path)
Note that using this feature means esbuild will potentially do a lot of file system I/O to find all possible files that might match the pattern. This is by design, and is not a bug. If this is a concern, I recommend either avoiding the
/**/
pattern (e.g. by not putting a/
before a wildcard) or using this feature only in directory subtrees which do not have many files that don't match the pattern (e.g. making a subdirectory for your JSON files and explicitly including that subdirectory in the pattern).
-
-
Path aliases in
tsconfig.json
no longer count as packages (#2792, #3003, #3160, #3238)Setting
--packages=external
tells esbuild to make all import paths external when they look like a package path. For example, an import of./foo/bar
is not a package path and won't be external while an import offoo/bar
is a package path and will be external. However, thepaths
field intsconfig.json
allows you to create import paths that look like package paths but that do not resolve to packages. People do not want these paths to count as package paths. So with this release, the behavior of--packages=external
has been changed to happen after thetsconfig.json
path remapping step. -
Use the
local-css
loader for.module.css
files by default (#20)With this release the
css
loader is still used for.css
files except that.module.css
files now use thelocal-css
loader. This is a common convention in the web development community. If you need.module.css
files to use thecss
loader instead, then you can override this behavior with--loader:.module.css=css
.
-
Support advanced CSS
@import
rules (#953, #3137)CSS
@import
statements have been extended to allow additional trailing tokens after the import path. These tokens sort of make the imported file behave as if it were wrapped in a@layer
,@supports
, and/or@media
rule. Here are some examples:@import url(foo.css); @import url(foo.css) layer; @import url(foo.css) layer(bar); @import url(foo.css) layer(bar) supports(display: flex); @import url(foo.css) layer(bar) supports(display: flex) print; @import url(foo.css) layer(bar) print; @import url(foo.css) supports(display: flex); @import url(foo.css) supports(display: flex) print; @import url(foo.css) print;
You can read more about this advanced syntax here. With this release, esbuild will now bundle
@import
rules with these trailing tokens and will wrap the imported files in the corresponding rules. Note that this now means a given imported file can potentially appear in multiple places in the bundle. However, esbuild will still only load it once (e.g. on-load plugins will only run once per file, not once per import).
-
Implement
composes
from CSS modules (#20)This release implements the
composes
annotation from the CSS modules specification. It provides a way for class selectors to reference other class selectors (assuming you are using thelocal-css
loader). And with thefrom
syntax, this can even work with local names across CSS files. For example:// app.js import { submit } from './style.css' const div = document.createElement('div') div.className = submit document.body.appendChild(div)
/* style.css */ .button { composes: pulse from "anim.css"; display: inline-block; } .submit { composes: button; font-weight: bold; }
/* anim.css */ @keyframes pulse { from, to { opacity: 1 } 50% { opacity: 0.5 } } .pulse { animation: 2s ease-in-out infinite pulse; }
Bundling this with esbuild using
--bundle --outdir=dist --loader:.css=local-css
now gives the following:(() => { // style.css var submit = "anim_pulse style_button style_submit"; // app.js var div = document.createElement("div"); div.className = submit; document.body.appendChild(div); })();
/* anim.css */ @keyframes anim_pulse { from, to { opacity: 1; } 50% { opacity: 0.5; } } .anim_pulse { animation: 2s ease-in-out infinite anim_pulse; } /* style.css */ .style_button { display: inline-block; } .style_submit { font-weight: bold; }
Import paths in the
composes: ... from
syntax are resolved using the newcomposes-from
import kind, which can be intercepted by plugins during import path resolution when bundling is enabled.Note that the order in which composed CSS classes from separate files appear in the bundled output file is deliberately undefined by design (see the specification for details). You are not supposed to declare the same CSS property in two separate class selectors and then compose them together. You are only supposed to compose CSS class selectors that declare non-overlapping CSS properties.
Issue #20 (the issue tracking CSS modules) is esbuild's most-upvoted issue! With this change, I now consider esbuild's implementation of CSS modules to be complete. There are still improvements to make and there may also be bugs with the current implementation, but these can be tracked in separate issues.
-
Fix non-determinism with
tsconfig.json
and symlinks (#3284)This release fixes an issue that could cause esbuild to sometimes emit incorrect build output in cases where a file under the effect of
tsconfig.json
is inconsistently referenced through a symlink. It can happen when usingnpm link
to create a symlink withinnode_modules
to an unpublished package. The build result was non-deterministic because esbuild runs module resolution in parallel and the result of thetsconfig.json
lookup depended on whether the import through the symlink or not through the symlink was resolved first. This problem was fixed by moving therealpath
operation before thetsconfig.json
lookup. -
Add a
hash
property to output files (#3084, #3293)As a convenience, every output file in esbuild's API now includes a
hash
property that is a hash of thecontents
field. This is the hash that's used internally by esbuild to detect changes between builds for esbuild's live-reload feature. You may also use it to detect changes between your own builds if its properties are sufficient for your use case.This feature has been added directly to output file objects since it's just a hash of the
contents
field, so it makes conceptual sense to store it in the same location. Another benefit of putting it there instead of including it as a part of the watch mode API is that it can be used without watch mode enabled. You can use it to compare the output of two independent builds that were done at different times.The hash algorithm (currently XXH64) is implementation-dependent and may be changed at any time in between esbuild versions. If you don't like esbuild's choice of hash algorithm then you are welcome to hash the contents yourself instead. As with any hash algorithm, note that while two different hashes mean that the contents are different, two equal hashes do not necessarily mean that the contents are equal. You may still want to compare the contents in addition to the hashes to detect with certainty when output files have been changed.
-
Avoid generating duplicate prefixed declarations in CSS (#3292)
There was a request for esbuild's CSS prefixer to avoid generating a prefixed declaration if a declaration by that name is already present in the same rule block. So with this release, esbuild will now avoid doing this:
/* Original code */ body { backdrop-filter: blur(30px); -webkit-backdrop-filter: blur(45px); } /* Old output (with --target=safari12) */ body { -webkit-backdrop-filter: blur(30px); backdrop-filter: blur(30px); -webkit-backdrop-filter: blur(45px); } /* New output (with --target=safari12) */ body { backdrop-filter: blur(30px); -webkit-backdrop-filter: blur(45px); }
This can result in a visual difference in certain cases (for example if the browser understands
blur(30px)
but notblur(45px)
, it will be able to fall back toblur(30px)
). But this change means esbuild now matches the behavior of Autoprefixer which is probably a good representation of how people expect this feature to work.
-
Fix asset references with the
--line-limit
flag (#3286)The recently-released
--line-limit
flag tells esbuild to terminate long lines after they pass this length limit. This includes automatically wrapping long strings across multiple lines using escaped newline syntax. However, using this could cause esbuild to generate incorrect code for references from generated output files to assets in the bundle (i.e. files loaded with thefile
orcopy
loaders). This is because esbuild implements asset references internally using find-and-replace with a randomly-generated string, but the find operation fails if the string is split by an escaped newline due to line wrapping. This release fixes the problem by not wrapping these strings. This issue affected asset references in both JS and CSS files. -
Support local names in CSS for
@keyframe
,@counter-style
, and@container
(#20)This release extends support for local names in CSS files loaded with the
local-css
loader to cover the@keyframe
,@counter-style
, and@container
rules (and alsoanimation
,list-style
, andcontainer
declarations). Here's an example:@keyframes pulse { from, to { opacity: 1 } 50% { opacity: 0.5 } } @counter-style moon { system: cyclic; symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔; } @container squish { li { float: left } } ul { animation: 2s ease-in-out infinite pulse; list-style: inside moon; container: squish / size; }
With the
local-css
loader enabled, that CSS will be turned into something like this (with the local name mapping exposed to JS):@keyframes stdin_pulse { from, to { opacity: 1; } 50% { opacity: 0.5; } } @counter-style stdin_moon { system: cyclic; symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔; } @container stdin_squish { li { float: left; } } ul { animation: 2s ease-in-out infinite stdin_pulse; list-style: inside stdin_moon; container: stdin_squish / size; }
If you want to use a global name within a file loaded with the
local-css
loader, you can use a:global
selector to do that:div { /* All symbols are global inside this scope (i.e. * "pulse", "moon", and "squish" are global below) */ :global { animation: 2s ease-in-out infinite pulse; list-style: inside moon; container: squish / size; } }
If you want to use
@keyframes
,@counter-style
, or@container
with a global name, make sure it's in a file that uses thecss
orglobal-css
loader instead of thelocal-css
loader. For example, you can configure--loader:.module.css=local-css
so that thelocal-css
loader only applies to*.module.css
files. -
Support strings as keyframe animation names in CSS (#2555)
With this release, esbuild will now parse animation names that are specified as strings and will convert them to identifiers. The CSS specification allows animation names to be specified using either identifiers or strings but Chrome only understands identifiers, so esbuild will now always convert string names to identifier names for Chrome compatibility:
/* Original code */ @keyframes "hide menu" { from { opacity: 1 } to { opacity: 0 } } menu.hide { animation: 0.5s ease-in-out "hide menu"; } /* Old output */ @keyframes "hide menu" { from { opacity: 1 } to { opacity: 0 } } menu.hide { animation: 0.5s ease-in-out "hide menu"; } /* New output */ @keyframes hide\ menu { from { opacity: 1; } to { opacity: 0; } } menu.hide { animation: 0.5s ease-in-out hide\ menu; }
-
Support
An+B
syntax and:nth-*()
pseudo-classes in CSSThis adds support for the
:nth-child()
,:nth-last-child()
,:nth-of-type()
, and:nth-last-of-type()
pseudo-classes to esbuild, which has the following consequences:- The
An+B
syntax is now parsed, so parse errors are now reported An+B
values inside these pseudo-classes are now pretty-printed (e.g. a leading+
will be stripped because it's not in the AST)- When minification is enabled,
An+B
values are reduced to equivalent but shorter forms (e.g.2n+0
=>2n
,2n+1
=>odd
) - Local CSS names in an
of
clause are now detected (e.g. in:nth-child(2n of :local(.foo))
the namefoo
is now renamed)
/* Original code */ .foo:nth-child(+2n+1 of :local(.bar)) { color: red; } /* Old output (with --loader=local-css) */ .stdin_foo:nth-child(+2n + 1 of :local(.bar)) { color: red; } /* New output (with --loader=local-css) */ .stdin_foo:nth-child(2n+1 of .stdin_bar) { color: red; }
- The
-
Adjust CSS nesting parser for IE7 hacks (#3272)
This fixes a regression with esbuild's treatment of IE7 hacks in CSS. CSS nesting allows selectors to be used where declarations are expected. There's an IE7 hack where prefixing a declaration with a
*
causes that declaration to only be applied in IE7 due to a bug in IE7's CSS parser. However, it's valid for nested CSS selectors to start with*
. So esbuild was incorrectly parsing these declarations and anything following it up until the next{
as a selector for a nested CSS rule. This release changes esbuild's parser to terminate the parsing of selectors for nested CSS rules when a;
is encountered to fix this edge case:/* Original code */ .item { *width: 100%; height: 1px; } /* Old output */ .item { *width: 100%; height: 1px; { } } /* New output */ .item { *width: 100%; height: 1px; }
Note that the syntax for CSS nesting is about to change again, so esbuild's CSS parser may still not be completely accurate with how browsers do and/or will interpret CSS nesting syntax. Expect additional updates to esbuild's CSS parser in the future to deal with upcoming CSS specification changes.
-
Adjust esbuild's warning about undefined imports for TypeScript
import
equals declarations (#3271)In JavaScript, accessing a missing property on an import namespace object is supposed to result in a value of
undefined
at run-time instead of an error at compile-time. This is something that esbuild warns you about by default because doing this can indicate a bug with your code. For example:// app.js import * as styles from './styles' console.log(styles.buton)
// styles.js export let button = {}
If you bundle
app.js
with esbuild you will get this:▲ [WARNING] Import "buton" will always be undefined because there is no matching export in "styles.js" [import-is-undefined] app.js:2:19: 2 │ console.log(styles.buton) │ ~~~~~ ╵ button Did you mean to import "button" instead? styles.js:1:11: 1 │ export let button = {} ╵ ~~~~~~
However, there is TypeScript-only syntax for
import
equals declarations that can represent either a type import (which esbuild should ignore) or a value import (which esbuild should respect). Since esbuild doesn't have a type system, it tries to only respectimport
equals declarations that are actually used as values. Previously esbuild always generated this warning for unused imports referenced withinimport
equals declarations even when the reference could be a type instead of a value. Starting with this release, esbuild will now only warn in this case if the import is actually used. Here is an example of some code that no longer causes an incorrect warning:// app.ts import * as styles from './styles' import ButtonType = styles.Button
// styles.ts export interface Button {}
-
Fix a regression with whitespace inside
:is()
(#3265)The change to parse the contents of
:is()
in version 0.18.14 introduced a regression that incorrectly flagged the contents as a syntax error if the contents started with a whitespace token (for examplediv:is( .foo ) {}
). This regression has been fixed.
-
Add the
--serve-fallback=
option (#2904)The web server built into esbuild serves the latest in-memory results of the configured build. If the requested path doesn't match any in-memory build result, esbuild also provides the
--servedir=
option to tell esbuild to serve the requested path from that directory instead. And if the requested path doesn't match either of those things, esbuild will either automatically generate a directory listing (for directories) or return a 404 error.Starting with this release, that last step can now be replaced with telling esbuild to serve a specific HTML file using the
--serve-fallback=
option. This can be used to provide a "not found" page for missing URLs. It can also be used to implement a single-page app that mutates the current URL and therefore requires the single app entry point to be served when the page is loaded regardless of whatever the current URL is. -
Use the
tsconfig
field inpackage.json
duringextends
resolution (#3247)This release adds a feature from TypeScript 3.2 where if a
tsconfig.json
file specifies a package name in theextends
field and that package'spackage.json
file has atsconfig
field, the contents of that field are used in the search for the basetsconfig.json
file. -
Implement CSS nesting without
:is()
when possible (#1945)Previously esbuild would always produce a warning when transforming nested CSS for a browser that doesn't support the
:is()
pseudo-class. This was because the nesting transform needs to generate an:is()
in some complex cases which means the transformed CSS would then not work in that browser. However, the CSS nesting transform can often be done without generating an:is()
. So with this release, esbuild will no longer warn when targeting browsers that don't support:is()
in the cases where an:is()
isn't needed to represent the nested CSS.In addition, esbuild's nested CSS transform has been updated to avoid generating an
:is()
in cases where an:is()
is preferable but there's a longer alternative that is also equivalent. This update means esbuild can now generate a combinatorial explosion of CSS for complex CSS nesting syntax when targeting browsers that don't support:is()
. This combinatorial explosion is necessary to accurately represent the original semantics. For example:/* Original code */ .first, .second, .third { & > & { color: red; } } /* Old output (with --target=chrome80) */ :is(.first, .second, .third) > :is(.first, .second, .third) { color: red; } /* New output (with --target=chrome80) */ .first > .first, .first > .second, .first > .third, .second > .first, .second > .second, .second > .third, .third > .first, .third > .second, .third > .third { color: red; }
This change means you can now use CSS nesting with esbuild when targeting an older browser that doesn't support
:is()
. You'll now only get a warning from esbuild if you use complex CSS nesting syntax that esbuild can't represent in that older browser without using:is()
. There are two such cases:/* Case 1 */ a b { .foo & { color: red; } } /* Case 2 */ a { > b& { color: red; } }
These two cases still need to use
:is()
, both for different reasons, and cannot be used when targeting an older browser that doesn't support:is()
:/* Case 1 */ .foo :is(a b) { color: red; } /* Case 2 */ a > a:is(b) { color: red; }
-
Automatically lower
inset
in CSS for older browsersWith this release, esbuild will now automatically expand the
inset
property to thetop
,right
,bottom
, andleft
properties when esbuild'starget
is set to a browser that doesn't supportinset
:/* Original code */ .app { position: absolute; inset: 10px 20px; } /* Old output (with --target=chrome80) */ .app { position: absolute; inset: 10px 20px; } /* New output (with --target=chrome80) */ .app { position: absolute; top: 10px; right: 20px; bottom: 10px; left: 20px; }
-
Add support for the new
@starting-style
CSS rule (#3249)This at rule allow authors to start CSS transitions on first style update. That is, you can now make the transition take effect when the
display
property changes fromnone
toblock
./* Original code */ @starting-style { h1 { background-color: transparent; } } /* Output */ @starting-style{h1{background-color:transparent}}
This was contributed by @yisibl.
-
Implement local CSS names (#20)
This release introduces two new loaders called
global-css
andlocal-css
and two new pseudo-class selectors:local()
and:global()
. This is a partial implementation of the popular CSS modules approach for avoiding unintentional name collisions in CSS. I'm not calling this feature "CSS modules" because although some people in the community call it that, other people in the community have started using "CSS modules" to refer to something completely different and now CSS modules is an overloaded term.Here's how this new local CSS name feature works with esbuild:
-
Identifiers that look like
.className
and#idName
are global with theglobal-css
loader and local with thelocal-css
loader. Global identifiers are the same across all files (the way CSS normally works) but local identifiers are different between different files. If two separate CSS files use the same local identifier.button
, esbuild will automatically rename one of them so that they don't collide. This is analogous to how esbuild automatically renames JS local variables with the same name in separate JS files to avoid name collisions. -
It only makes sense to use local CSS names with esbuild when you are also using esbuild's bundler to bundle JS files that import CSS files. When you do that, esbuild will generate one export for each local name in the CSS file. The JS code can import these names and use them when constructing HTML DOM. For example:
// app.js import { outerShell } from './app.css' const div = document.createElement('div') div.className = outerShell document.body.appendChild(div)
/* app.css */ .outerShell { position: absolute; inset: 0; }
When you bundle this with
esbuild app.js --bundle --loader:.css=local-css --outdir=out
you'll now get this (notice how the local CSS nameouterShell
has been renamed):// out/app.js (() => { // app.css var outerShell = "app_outerShell"; // app.js var div = document.createElement("div"); div.className = outerShell; document.body.appendChild(div); })();
/* out/app.css */ .app_outerShell { position: absolute; inset: 0; }
This feature only makes sense to use when bundling is enabled both because your code needs to
import
the renamed local names so that it can use them, and because esbuild needs to be able to process all CSS files containing local names in a single bundling operation so that it can successfully rename conflicting local names to avoid collisions. -
If you are in a global CSS file (with the
global-css
loader) you can create a local name using:local()
, and if you are in a local CSS file (with thelocal-css
loader) you can create a global name with:global()
. So the choice of theglobal-css
loader vs. thelocal-css
loader just sets the default behavior for identifiers, but you can override it on a case-by-case basis as necessary. For example::local(.button) { color: red; } :global(.button) { color: blue; }
Processing this CSS file with esbuild with either the
global-css
orlocal-css
loader will result in something like this:.stdin_button { color: red; } .button { color: blue; }
-
The names that esbuild generates for local CSS names are an implementation detail and are not intended to be hard-coded anywhere. The only way you should be referencing the local CSS names in your JS or HTML is with an
import
statement in JS that is bundled with esbuild, as demonstrated above. For example, when--minify
is enabled esbuild will use a different name generation algorithm which generates names that are as short as possible (analogous to how esbuild minifies local identifiers in JS). -
You can easily use both global CSS files and local CSS files simultaneously if you give them different file extensions. For example, you could pass
--loader:.css=global-css
and--loader:.module.css=local-css
to esbuild so that.css
files still use global names by default but.module.css
files use local names by default. -
Keep in mind that the
css
loader is different than theglobal-css
loader. The:local
and:global
annotations are not enabled with thecss
loader and will be passed through unchanged. This allows you to have the option of using esbuild to process CSS containing while preserving these annotations. It also means that local CSS names are disabled by default for now (since thecss
loader is currently the default for CSS files). The:local
and:global
syntax may be enabled by default in a future release.
Note that esbuild's implementation does not currently have feature parity with other implementations of modular CSS in similar tools. This is only a preliminary release with a partial implementation that includes some basic behavior to get the process started. Additional behavior may be added in future releases. In particular, this release does not implement:
- The
composes
pragma - Tree shaking for unused local CSS
- Local names for keyframe animations, grid lines,
@container
,@counter-style
, etc.
Issue #20 (the issue for this feature) is esbuild's most-upvoted issue! While this release still leaves that issue open, it's an important first step in that direction.
-
-
Parse
:is
,:has
,:not
, and:where
in CSSWith this release, esbuild will now parse the contents of these pseudo-class selectors as a selector list. This means you will now get syntax warnings within these selectors for invalid selector syntax. It also means that esbuild's CSS nesting transform behaves slightly differently than before because esbuild is now operating on an AST instead of a token stream. For example:
/* Original code */ div { :where(.foo&) { color: red; } } /* Old output (with --target=chrome90) */ :where(.foo:is(div)) { color: red; } /* New output (with --target=chrome90) */ :where(div.foo) { color: red; }
-
Add the
--drop-labels=
option (#2398)If you want to conditionally disable some development-only code and have it not be present in the final production bundle, right now the most straightforward way of doing this is to use the
--define:
flag along with a specially-named global variable. For example, consider the following code:function main() { DEV && doAnExpensiveCheck() }
You can build this for development and production like this:
- Development:
esbuild --define:DEV=true
- Production:
esbuild --define:DEV=false
One drawback of this approach is that the resulting code crashes if you don't provide a value for
DEV
with--define:
. In practice this isn't that big of a problem, and there are also various ways to work around this.However, another approach that avoids this drawback is to use JavaScript label statements instead. That's what the
--drop-labels=
flag implements. For example, consider the following code:function main() { DEV: doAnExpensiveCheck() }
With this release, you can now build this for development and production like this:
- Development:
esbuild
- Production:
esbuild --drop-labels=DEV
This means that code containing optional development-only checks can now be written such that it's safe to run without any additional configuration. The
--drop-labels=
flag takes comma-separated list of multiple label names to drop. - Development:
-
Avoid causing
unhandledRejection
during shutdown (#3219)All pending esbuild JavaScript API calls are supposed to fail if esbuild's underlying child process is unexpectedly terminated. This can happen if
SIGINT
is sent to the parentnode
process with Ctrl+C, for example. Previously doing this could also cause an unhandled promise rejection when esbuild attempted to communicate this failure to its own child process that no longer exists. This release now swallows this communication failure, which should prevent this internal unhandled promise rejection. This change means that you can now use esbuild's JavaScript API with a customSIGINT
handler that extends the lifetime of thenode
process without esbuild's internals causing an early exit due to an unhandled promise rejection. -
Update browser compatibility table scripts
The scripts that esbuild uses to compile its internal browser compatibility table have been overhauled. Briefly:
- Converted from JavaScript to TypeScript
- Fixed some bugs that resulted in small changes to the table
- Added
caniuse-lite
and@mdn/browser-compat-data
as new data sources (replacing manually-copied information)
This change means it's now much easier to keep esbuild's internal compatibility tables up to date. You can review the table changes here if you need to debug something about this change:
-
Fix a panic with
const enum
inside parentheses (#3205)This release fixes an edge case where esbuild could potentially panic if a TypeScript
const enum
statement was used inside of a parenthesized expression and was followed by certain other scope-related statements. Here's a minimal example that triggers this edge case:(() => { const enum E { a }; () => E.a })
-
Allow a newline in the middle of TypeScript
export type
statement (#3225)Previously esbuild incorrectly rejected the following valid TypeScript code:
export type { T }; export type * as foo from 'bar';
Code that uses a newline after
export type
is now allowed starting with this release. -
Fix cross-module inlining of string enums (#3210)
A refactoring typo in version 0.18.9 accidentally introduced a regression with cross-module inlining of string enums when combined with computed property accesses. This regression has been fixed.
-
Rewrite
.js
to.ts
inside packages withexports
(#3201)Packages with the
exports
field are supposed to disable node's path resolution behavior that allows you to import a file with a different extension than the one in the source code (for example, importingfoo/bar
to getfoo/bar.js
). And TypeScript has behavior where you can import a non-existent.js
file and you will get the.ts
file instead. Previously the presence of theexports
field caused esbuild to disable all extension manipulation stuff which included both node's implicit file extension searching and TypeScript's file extension swapping. However, TypeScript appears to always apply file extension swapping even in this case. So with this release, esbuild will now rewrite.js
to.ts
even inside packages withexports
. -
Fix a redirect edge case in esbuild's development server (#3208)
The development server canonicalizes directory URLs by adding a trailing slash. For example, visiting
/about
redirects to/about/
if/about/index.html
would be served. However, if the requested path begins with two slashes, then the redirect incorrectly turned into a protocol-relative URL. For example, visiting//about
redirected to//about/
which the browser turns intohttp://about/
. This release fixes the bug by canonicalizing the URL path when doing this redirect.
-
Fix a TypeScript code generation edge case (#3199)
This release fixes a regression in version 0.18.4 where using a TypeScript
namespace
that exports aclass
declaration combined with--keep-names
and a--target
ofes2021
or earlier could cause esbuild to export the class from the namespace using an incorrect name (notice the assignment toX2._Y
vs.X2.Y
):// Original code // Old output (with --keep-names --target=es2021) var X; ((X2) => { const _Y = class _Y { }; __name(_Y, "Y"); let Y = _Y; X2._Y = _Y; })(X || (X = {})); // New output (with --keep-names --target=es2021) var X; ((X2) => { const _Y = class _Y { }; __name(_Y, "Y"); let Y = _Y; X2.Y = _Y; })(X || (X = {}));
-
Fix a tree-shaking bug that removed side effects (#3195)
This fixes a regression in version 0.18.4 where combining
--minify-syntax
with--keep-names
could cause expressions with side effects after a function declaration to be considered side-effect free for tree shaking purposes. The reason was because--keep-names
generates an expression statement containing a call to a helper function after the function declaration with a special flag that makes the function call able to be tree shaken, and then--minify-syntax
could potentially merge that expression statement with following expressions without clearing the flag. This release fixes the bug by clearing the flag when merging expression statements together. -
Fix an incorrect warning about CSS nesting (#3197)
A warning is currently generated when transforming nested CSS to a browser that doesn't support
:is()
because transformed nested CSS may need to use that feature to represent nesting. This was previously always triggered when an at-rule was encountered in a declaration context. Typically the only case you would encounter this is when using CSS nesting within a selector rule. However, there is a case where that's not true: when using a margin at-rule such as@top-left
within@page
. This release avoids incorrectly generating a warning in this case by checking that the at-rule is within a selector rule before generating a warning.
-
Fix
await using
declarations insideasync
generator functionsI forgot about the new
await using
declarations when implementing lowering forasync
generator functions in the previous release. This change fixes the transformation ofawait using
declarations when they are inside loweredasync
generator functions:// Original code async function* foo() { await using x = await y } // Old output (with --supported:async-generator=false) function foo() { return __asyncGenerator(this, null, function* () { await using x = yield new __await(y); }); } // New output (with --supported:async-generator=false) function foo() { return __asyncGenerator(this, null, function* () { var _stack = []; try { const x = __using(_stack, yield new __await(y), true); } catch (_) { var _error = _, _hasError = true; } finally { var _promise = __callDispose(_stack, _error, _hasError); _promise && (yield new __await(_promise)); } }); }
-
Insert some prefixed CSS properties when appropriate (#3122)
With this release, esbuild will now insert prefixed CSS properties in certain cases when the
target
setting includes browsers that require a certain prefix. This is currently done for the following properties:appearance: *;
=>-webkit-appearance: *; -moz-appearance: *;
backdrop-filter: *;
=>-webkit-backdrop-filter: *;
background-clip: text
=>-webkit-background-clip: text;
box-decoration-break: *;
=>-webkit-box-decoration-break: *;
clip-path: *;
=>-webkit-clip-path: *;
font-kerning: *;
=>-webkit-font-kerning: *;
hyphens: *;
=>-webkit-hyphens: *;
initial-letter: *;
=>-webkit-initial-letter: *;
mask-image: *;
=>-webkit-mask-image: *;
mask-origin: *;
=>-webkit-mask-origin: *;
mask-position: *;
=>-webkit-mask-position: *;
mask-repeat: *;
=>-webkit-mask-repeat: *;
mask-size: *;
=>-webkit-mask-size: *;
position: sticky;
=>position: -webkit-sticky;
print-color-adjust: *;
=>-webkit-print-color-adjust: *;
tab-size: *;
=>-moz-tab-size: *; -o-tab-size: *;
text-decoration-color: *;
=>-webkit-text-decoration-color: *; -moz-text-decoration-color: *;
text-decoration-line: *;
=>-webkit-text-decoration-line: *; -moz-text-decoration-line: *;
text-decoration-skip: *;
=>-webkit-text-decoration-skip: *;
text-emphasis-color: *;
=>-webkit-text-emphasis-color: *;
text-emphasis-position: *;
=>-webkit-text-emphasis-position: *;
text-emphasis-style: *;
=>-webkit-text-emphasis-style: *;
text-orientation: *;
=>-webkit-text-orientation: *;
text-size-adjust: *;
=>-webkit-text-size-adjust: *; -ms-text-size-adjust: *;
user-select: *;
=>-webkit-user-select: *; -moz-user-select: *; -ms-user-select: *;
Here is an example:
/* Original code */ div { mask-image: url(x.png); } /* Old output (with --target=chrome99) */ div { mask-image: url(x.png); } /* New output (with --target=chrome99) */ div { -webkit-mask-image: url(x.png); mask-image: url(x.png); }
Browser compatibility data was sourced from the tables on https://caniuse.com. Support for more CSS properties can be added in the future as appropriate.
-
Fix an obscure identifier minification bug (#2809)
Function declarations in nested scopes behave differently depending on whether or not
"use strict"
is present. To avoid generating code that behaves differently depending on whether strict mode is enabled or not, esbuild transforms nested function declarations into variable declarations. However, there was a bug where the generated variable name was not being recorded as declared internally, which meant that it wasn't being renamed correctly by the minifier and could cause a name collision. This bug has been fixed:// Original code const n = '' for (let i of [0,1]) { function f () {} } // Old output (with --minify-identifiers --format=esm) const f = ""; for (let o of [0, 1]) { let n = function() { }; var f = n; } // New output (with --minify-identifiers --format=esm) const f = ""; for (let o of [0, 1]) { let n = function() { }; var t = n; }
-
Fix a bug in esbuild's compatibility table script (#3179)
Setting esbuild's
target
to a specific JavaScript engine tells esbuild to use the JavaScript syntax feature compatibility data from https://kangax.github.io/compat-table/es6/ for that engine to determine which syntax features to allow. However, esbuild's script that builds this internal compatibility table had a bug that incorrectly ignores tests for engines that still have outstanding implementation bugs which were never fixed. This change fixes this bug with the script.The only case where this changed the information in esbuild's internal compatibility table is that the
hermes
target is marked as no longer supporting destructuring. This is because there is a failing destructuring-related test for Hermes on https://kangax.github.io/compat-table/es6/. If you want to use destructuring with Hermes anyway, you can pass--supported:destructuring=true
to esbuild to override thehermes
target and force esbuild to accept this syntax.This fix was contributed by @ArrayZoneYour.
-
Implement transforming
async
generator functions (#2780)With this release, esbuild will now transform
async
generator functions into normal generator functions when the configured target environment doesn't support them. These functions behave similar to normal generator functions except that they use theSymbol.asyncIterator
interface instead of theSymbol.iterator
interface and the iteration methods return promises. Here's an example (helper functions are omitted):// Original code async function* foo() { yield Promise.resolve(1) await new Promise(r => setTimeout(r, 100)) yield *[Promise.resolve(2)] } async function bar() { for await (const x of foo()) { console.log(x) } } bar() // New output (with --target=es6) function foo() { return __asyncGenerator(this, null, function* () { yield Promise.resolve(1); yield new __await(new Promise((r) => setTimeout(r, 100))); yield* __yieldStar([Promise.resolve(2)]); }); } function bar() { return __async(this, null, function* () { try { for (var iter = __forAwait(foo()), more, temp, error; more = !(temp = yield iter.next()).done; more = false) { const x = temp.value; console.log(x); } } catch (temp) { error = [temp]; } finally { try { more && (temp = iter.return) && (yield temp.call(iter)); } finally { if (error) throw error[0]; } } }); } bar();
This is an older feature that was added to JavaScript in ES2018 but I didn't implement the transformation then because it's a rarely-used feature. Note that esbuild already added support for transforming
for await
loops (the other part of the asynchronous iteration proposal) a year ago, so support for asynchronous iteration should now be complete.I have never used this feature myself and code that uses this feature is hard to come by, so this transformation has not yet been tested on real-world code. If you do write code that uses this feature, please let me know if esbuild's
async
generator transformation doesn't work with your code.
-
Add support for
using
declarations in TypeScript 5.2+ (#3191)TypeScript 5.2 (due to be released in August of 2023) will introduce
using
declarations, which will allow you to automatically dispose of the declared resources when leaving the current scope. You can read the TypeScript PR for this feature for more information. This release of esbuild adds support for transforming this syntax to target environments without support forusing
declarations (which is currently all targets other thanesnext
). Here's an example (helper functions are omitted):// Original code class Foo { [Symbol.dispose]() { console.log('cleanup') } } using foo = new Foo; foo.bar(); // New output (with --target=es6) var _stack = []; try { var Foo = class { [Symbol.dispose]() { console.log("cleanup"); } }; var foo = __using(_stack, new Foo()); foo.bar(); } catch (_) { var _error = _, _hasError = true; } finally { __callDispose(_stack, _error, _hasError); }
The injected helper functions ensure that the method named
Symbol.dispose
is called onnew Foo
when control exits the scope. Note that as with all new JavaScript APIs, you'll need to polyfillSymbol.dispose
if it's not present before you use it. This is not something that esbuild does for you because esbuild only handles syntax, not APIs. Polyfilling it can be done with something like this:Symbol.dispose ||= Symbol('Symbol.dispose')
This feature also introduces
await using
declarations which are likeusing
declarations but they callawait
on the disposal method (not on the initializer). Here's an example (helper functions are omitted):// Original code class Foo { async [Symbol.asyncDispose]() { await new Promise(done => { setTimeout(done, 1000) }) console.log('cleanup') } } await using foo = new Foo; foo.bar(); // New output (with --target=es2022) var _stack = []; try { var Foo = class { async [Symbol.asyncDispose]() { await new Promise((done) => { setTimeout(done, 1e3); }); console.log("cleanup"); } }; var foo = __using(_stack, new Foo(), true); foo.bar(); } catch (_) { var _error = _, _hasError = true; } finally { var _promise = __callDispose(_stack, _error, _hasError); _promise && await _promise; }
The injected helper functions ensure that the method named
Symbol.asyncDispose
is called onnew Foo
when control exits the scope, and that the returned promise is awaited. Similarly toSymbol.dispose
, you'll also need to polyfillSymbol.asyncDispose
before you use it. -
Add a
--line-limit=
flag to limit line length (#3170)Long lines are common in minified code. However, many tools and text editors can't handle long lines. This release introduces the
--line-limit=
flag to tell esbuild to wrap lines longer than the provided number of bytes. For example,--line-limit=80
tells esbuild to insert a newline soon after a given line reaches 80 bytes in length. This setting applies to both JavaScript and CSS, and works even when minification is disabled. Note that turning this setting on will make your files bigger, as the extra newlines take up additional space in the file (even after gzip compression).
-
Fix tree-shaking of classes with decorators (#3164)
This release fixes a bug where esbuild incorrectly allowed tree-shaking on classes with decorators. Each decorator is a function call, so classes with decorators must never be tree-shaken. This bug was a regression that was unintentionally introduced in version 0.18.2 by the change that enabled tree-shaking of lowered private fields. Previously decorators were always lowered, and esbuild always considered the automatically-generated decorator code to be a side effect. But this is no longer the case now that esbuild analyzes side effects using the AST before lowering takes place. This bug was fixed by considering any decorator a side effect.
-
Fix a minification bug involving function expressions (#3125)
When minification is enabled, esbuild does limited inlining of
const
symbols at the top of a scope. This release fixes a bug where inlineable symbols were incorrectly removed assuming that they were inlined. They may not be inlined in cases where they were referenced by earlier constants in the body of a function expression. The declarations involved in these edge cases are now kept instead of being removed:// Original code { const fn = () => foo const foo = 123 console.log(fn) } // Old output (with --minify-syntax) console.log((() => foo)()); // New output (with --minify-syntax) { const fn = () => foo, foo = 123; console.log(fn); }
-
Implement auto accessors (#3009)
This release implements the new auto-accessor syntax from the upcoming JavaScript decorators proposal. The auto-accessor syntax looks like this:
class Foo { accessor foo; static accessor bar; } new Foo().foo = Foo.bar;
This syntax is not yet a part of JavaScript but it was added to TypeScript in version 4.9. More information about this feature can be found in microsoft/TypeScript#49705. Auto-accessors will be transformed if the target is set to something other than
esnext
:// Output (with --target=esnext) class Foo { accessor foo; static accessor bar; } new Foo().foo = Foo.bar; // Output (with --target=es2022) class Foo { #foo; get foo() { return this.#foo; } set foo(_) { this.#foo = _; } static #bar; static get bar() { return this.#bar; } static set bar(_) { this.#bar = _; } } new Foo().foo = Foo.bar; // Output (with --target=es2021) var _foo, _bar; class Foo { constructor() { __privateAdd(this, _foo, void 0); } get foo() { return __privateGet(this, _foo); } set foo(_) { __privateSet(this, _foo, _); } static get bar() { return __privateGet(this, _bar); } static set bar(_) { __privateSet(this, _bar, _); } } _foo = new WeakMap(); _bar = new WeakMap(); __privateAdd(Foo, _bar, void 0); new Foo().foo = Foo.bar;
You can also now use auto-accessors with esbuild's TypeScript experimental decorator transformation, which should behave the same as decorating the underlying getter/setter pair.
Please keep in mind that this syntax is not yet part of JavaScript. This release enables auto-accessors in
.js
files with the expectation that it will be a part of JavaScript soon. However, esbuild may change or remove this feature in the future if JavaScript ends up changing or removing this feature. Use this feature with caution for now. -
Pass through JavaScript decorators (#104)
In this release, esbuild now parses decorators from the upcoming JavaScript decorators proposal and passes them through to the output unmodified (as long as the language target is set to
esnext
). Transforming JavaScript decorators to environments that don't support them has not been implemented yet. The only decorator transform that esbuild currently implements is still the TypeScript experimental decorator transform, which only works in.ts
files and which requires"experimentalDecorators": true
in yourtsconfig.json
file. -
Static fields with assign semantics now use static blocks if possible
Setting
useDefineForClassFields
to false in TypeScript requires rewriting class fields to assignment statements. Previously this was done by removing the field from the class body and adding an assignment statement after the class declaration. However, this also caused any private fields to also be lowered by necessity (in case a field initializer uses a private symbol, either directly or indirectly). This release changes this transform to use an inline static block if it's supported, which avoids needing to lower private fields in this scenario:// Original code class Test { static #foo = 123 static bar = this.#foo } // Old output (with useDefineForClassFields=false) var _foo; const _Test = class _Test { }; _foo = new WeakMap(); __privateAdd(_Test, _foo, 123); _Test.bar = __privateGet(_Test, _foo); let Test = _Test; // New output (with useDefineForClassFields=false) class Test { static #foo = 123; static { this.bar = this.#foo; } }
-
Fix TypeScript experimental decorators combined with
--mangle-props
(#3177)Previously using TypeScript experimental decorators combined with the
--mangle-props
setting could result in a crash, as the experimental decorator transform was not expecting a mangled property as a class member. This release fixes the crash so you can now combine both of these features together safely.
-
Bundling no longer unnecessarily transforms class syntax (#1360, #1328, #1524, #2416)
When bundling, esbuild automatically converts top-level class statements to class expressions. Previously this conversion had the unfortunate side-effect of also transforming certain other class-related syntax features to avoid correctness issues when the references to the class name within the class body. This conversion has been reworked to avoid doing this:
// Original code export class Foo { static foo = () => Foo } // Old output (with --bundle) var _Foo = class { }; var Foo = _Foo; __publicField(Foo, "foo", () => _Foo); // New output (with --bundle) var Foo = class _Foo { static foo = () => _Foo; };
This conversion process is very complicated and has many edge cases (including interactions with static fields, static blocks, private class properties, and TypeScript experimental decorators). It should already be pretty robust but a change like this may introduce new unintentional behavior. Please report any issues with this upgrade on the esbuild bug tracker.
You may be wondering why esbuild needs to do this at all. One reason to do this is that esbuild's bundler sometimes needs to lazily-evaluate a module. For example, a module may end up being both the target of a dynamic
import()
call and a staticimport
statement. Lazy module evaluation is done by wrapping the top-level module code in a closure. To avoid a performance hit for staticimport
statements, esbuild stores top-level exported symbols outside of the closure and references them directly instead of indirectly.Another reason to do this is that multiple JavaScript VMs have had and continue to have performance issues with TDZ (i.e. "temporal dead zone") checks. These checks validate that a let, or const, or class symbol isn't used before it's initialized. Here are two issues with well-known VMs:
- V8: https://bugs.chromium.org/p/v8/issues/detail?id=13723 (10% slowdown)
- JavaScriptCore: https://bugs.webkit.org/show_bug.cgi?id=199866 (1,000% slowdown!)
JavaScriptCore had a severe performance issue as their TDZ implementation had time complexity that was quadratic in the number of variables needing TDZ checks in the same scope (with the top-level scope typically being the worst offender). V8 has ongoing issues with TDZ checks being present throughout the code their JIT generates even when they have already been checked earlier in the same function or when the function in question has already been run (so the checks have already happened).
Due to esbuild's parallel architecture, esbuild both a) needs to convert class statements into class expressions during parsing and b) doesn't yet know whether this module will need to be lazily-evaluated or not in the parser. So esbuild always does this conversion during bundling in case it's needed for correctness (and also to avoid potentially catastrophic performance issues due to bundling creating a large scope with many TDZ variables).
-
Enforce TDZ errors in computed class property keys (#2045)
JavaScript allows class property keys to be generated at run-time using code, like this:
class Foo { static foo = 'foo' static [Foo.foo + '2'] = 2 }
Previously esbuild treated references to the containing class name within computed property keys as a reference to the partially-initialized class object. That meant code that attempted to reference properties of the class object (such as the code above) would get back
undefined
instead of throwing an error.This release rewrites references to the containing class name within computed property keys into code that always throws an error at run-time, which is how this JavaScript code is supposed to work. Code that does this will now also generate a warning. You should never write code like this, but it now should be more obvious when incorrect code like this is written.
-
Fix an issue with experimental decorators and static fields (#2629)
This release also fixes a bug regarding TypeScript experimental decorators and static class fields which reference the enclosing class name in their initializer. This affected top-level classes when bundling was enabled. Previously code that does this could crash because the class name wasn't initialized yet. This case should now be handled correctly:
// Original code class Foo { @someDecorator static foo = 'foo' static bar = Foo.foo.length } // Old output const _Foo = class { static foo = "foo"; static bar = _Foo.foo.length; }; let Foo = _Foo; __decorateClass([ someDecorator ], Foo, "foo", 2); // New output const _Foo = class _Foo { static foo = "foo"; static bar = _Foo.foo.length; }; __decorateClass([ someDecorator ], _Foo, "foo", 2); let Foo = _Foo;
-
Fix a minification regression with negative numeric properties (#3169)
Version 0.18.0 introduced a regression where computed properties with negative numbers were incorrectly shortened into a non-computed property when minification was enabled. This regression has been fixed:
// Original code x = { [1]: 1, [-1]: -1, [NaN]: NaN, [Infinity]: Infinity, [-Infinity]: -Infinity, } // Old output (with --minify) x={1:1,-1:-1,NaN:NaN,1/0:1/0,-1/0:-1/0}; // New output (with --minify) x={1:1,[-1]:-1,NaN:NaN,[1/0]:1/0,[-1/0]:-1/0};
-
Fix a panic due to empty static class blocks (#3161)
This release fixes a bug where an internal invariant that was introduced in the previous release was sometimes violated, which then caused a panic. It happened when bundling code containing an empty static class block with both minification and bundling enabled.
-
Lower static blocks when static fields are lowered (#2800, #2950, #3025)
This release fixes a bug where esbuild incorrectly did not lower static class blocks when static class fields needed to be lowered. For example, the following code should print
1 2 3
but previously printed2 1 3
instead due to this bug:// Original code class Foo { static x = console.log(1) static { console.log(2) } static y = console.log(3) } // Old output (with --supported:class-static-field=false) class Foo { static { console.log(2); } } __publicField(Foo, "x", console.log(1)); __publicField(Foo, "y", console.log(3)); // New output (with --supported:class-static-field=false) class Foo { } __publicField(Foo, "x", console.log(1)); console.log(2); __publicField(Foo, "y", console.log(3));
-
Use static blocks to implement
--keep-names
on classes (#2389)This change fixes a bug where the
name
property could previously be incorrect within a class static context when using--keep-names
. The problem was that thename
property was being initialized after static blocks were run instead of before. This has been fixed by moving thename
property initializer into a static block at the top of the class body:// Original code if (typeof Foo === 'undefined') { let Foo = class { static test = this.name } console.log(Foo.test) } // Old output (with --keep-names) if (typeof Foo === "undefined") { let Foo2 = /* @__PURE__ */ __name(class { static test = this.name; }, "Foo"); console.log(Foo2.test); } // New output (with --keep-names) if (typeof Foo === "undefined") { let Foo2 = class { static { __name(this, "Foo"); } static test = this.name; }; console.log(Foo2.test); }
This change was somewhat involved, especially regarding what esbuild considers to be side-effect free. Some unused classes that weren't removed by tree shaking in previous versions of esbuild may now be tree-shaken. One example is classes with static private fields that are transformed by esbuild into code that doesn't use JavaScript's private field syntax. Previously esbuild's tree shaking analysis ran on the class after syntax lowering, but with this release it will run on the class before syntax lowering, meaning it should no longer be confused by class mutations resulting from automatically-generated syntax lowering code.
-
Fill in
null
entries in input source maps (#3144)If esbuild bundles input files with source maps and those source maps contain a
sourcesContent
array withnull
entries, esbuild previously copied thosenull
entries over to the output source map. With this release, esbuild will now attempt to fill in thosenull
entries by looking for a file on the file system with the corresponding name from thesources
array. This matches esbuild's existing behavior that automatically generates thesourcesContent
array from the file system if the entiresourcesContent
array is missing. -
Support
/* @__KEY__ */
comments for mangling property names (#2574)Property mangling is an advanced feature that enables esbuild to minify certain property names, even though it's not possible to automatically determine that it's safe to do so. The safe property names are configured via regular expression such as
--mangle-props=_$
(mangle all properties ending in_
).Sometimes it's desirable to also minify strings containing property names, even though it's not possible to automatically determine which strings are property names. This release makes it possible to do this by annotating those strings with
/* @__KEY__ */
. This is a convention that Terser added earlier this year, and which esbuild is now following too: terser/terser#1365. Using it looks like this:// Original code console.log( [obj.mangle_, obj.keep], [obj.get('mangle_'), obj.get('keep')], [obj.get(/* @__KEY__ */ 'mangle_'), obj.get(/* @__KEY__ */ 'keep')], ) // Old output (with --mangle-props=_$) console.log( [obj.a, obj.keep], [obj.get("mangle_"), obj.get("keep")], [obj.get(/* @__KEY__ */ "mangle_"), obj.get(/* @__KEY__ */ "keep")] ); // New output (with --mangle-props=_$) console.log( [obj.a, obj.keep], [obj.get("mangle_"), obj.get("keep")], [obj.get(/* @__KEY__ */ "a"), obj.get(/* @__KEY__ */ "keep")] );
-
Support
/* @__NO_SIDE_EFFECTS__ */
comments for functions (#3149)Rollup has recently added support for
/* @__NO_SIDE_EFFECTS__ */
annotations before functions to indicate that calls to these functions can be removed if the result is unused (i.e. the calls can be assumed to have no side effects). This release adds basic support for these to esbuild as well, which means esbuild will now parse these comments in input files and preserve them in output files. This should help people that use esbuild in combination with Rollup.Note that this doesn't necessarily mean esbuild will treat these calls as having no side effects, as esbuild's parallel architecture currently isn't set up to enable this type of cross-file tree-shaking information (tree-shaking decisions regarding a function call are currently local to the file they appear in). If you want esbuild to consider a function call to have no side effects, make sure you continue to annotate the function call with
/* @__PURE__ */
(which is the previously-established convention for communicating this).
This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild
in your package.json
file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.17.0
or ~0.17.0
. See npm's documentation about semver for more information.
The breaking changes in this release mainly focus on fixing some long-standing issues with esbuild's handling of tsconfig.json
files. Here are all the changes in this release, in detail:
-
Add a way to try esbuild online (#797)
There is now a way to try esbuild live on esbuild's website without installing it: https://esbuild.github.io/try/. In addition to being able to more easily evaluate esbuild, this should also make it more efficient to generate esbuild bug reports. For example, you can use it to compare the behavior of different versions of esbuild on the same input. The state of the page is stored in the URL for easy sharing. Many thanks to @hyrious for creating https://hyrious.me/esbuild-repl/, which was the main inspiration for this addition to esbuild's website.
Two forms of build options are supported: either CLI-style (example) or JS-style (example). Both are converted into a JS object that's passed to esbuild's WebAssembly API. The CLI-style argument parser is a custom one that simulates shell quoting rules, and the JS-style argument parser is also custom and parses a superset of JSON (basically JSON5 + regular expressions). So argument parsing is an approximate simulation of what happens for real but hopefully it should be close enough.
-
Changes to esbuild's
tsconfig.json
support (#3019):This release makes the following changes to esbuild's
tsconfig.json
support:-
Using experimental decorators now requires
"experimentalDecorators": true
(#104)Previously esbuild would always compile decorators in TypeScript code using TypeScript's experimental decorator transform. Now that standard JavaScript decorators are close to being finalized, esbuild will now require you to use
"experimentalDecorators": true
to do this. This new requirement makes it possible for esbuild to introduce a transform for standard JavaScript decorators in TypeScript code in the future. Such a transform has not been implemented yet, however. -
TypeScript's
target
no longer affects esbuild'starget
(#2628)Some people requested that esbuild support TypeScript's
target
setting, so support for it was added (in version 0.12.4). However, esbuild supports reading from multipletsconfig.json
files within a single build, which opens up the possibility that different files in the build have different language targets configured. There isn't really any reason to do this and it can lead to unexpected results. So with this release, thetarget
setting intsconfig.json
will no longer affect esbuild's owntarget
setting. You will have to use esbuild's own target setting instead (which is a single, global value). -
TypeScript's
jsx
setting no longer causes esbuild to preserve JSX syntax (#2634)TypeScript has a setting called
jsx
that controls how to transform JSX into JS. The tool-agnostic transform is calledreact
, and the React-specific transform is calledreact-jsx
(orreact-jsxdev
). There is also a setting calledpreserve
which indicates JSX should be passed through untransformed. Previously people would run esbuild with"jsx": "preserve"
in theirtsconfig.json
files and then be surprised when esbuild preserved their JSX. So with this release, esbuild will now ignore"jsx": "preserve"
intsconfig.json
files. If you want to preserve JSX syntax with esbuild, you now have to use--jsx=preserve
.Note: Some people have suggested that esbuild's equivalent
jsx
setting override the one intsconfig.json
. However, some projects need to legitimately have different files within the same build use different transforms (i.e.react
vs.react-jsx
) and having esbuild's globaljsx
setting overridetsconfig.json
would prevent this from working. This release ignores"jsx": "preserve"
but still allows otherjsx
values intsconfig.json
files to override esbuild's globaljsx
setting to keep the ability for multiple files within the same build to use different transforms. -
useDefineForClassFields
behavior has changed (#2584, #2993)Class fields in TypeScript look like this (
x
is a class field):class Foo { x = 123 }
TypeScript has legacy behavior that uses assignment semantics instead of define semantics for class fields when
useDefineForClassFields
is enabled (in which case class fields in TypeScript behave differently than they do in JavaScript, which is arguably "wrong").This legacy behavior exists because TypeScript added class fields to TypeScript before they were added to JavaScript. The TypeScript team decided to go with assignment semantics and shipped their implementation. Much later on TC39 decided to go with define semantics for class fields in JavaScript instead. This behaves differently if the base class has a setter with the same name:
class Base { set x(_) { console.log('x:', _) } } // useDefineForClassFields: false class AssignSemantics extends Base { constructor() { super() this.x = 123 } } // useDefineForClassFields: true class DefineSemantics extends Base { constructor() { super() Object.defineProperty(this, 'x', { value: 123 }) } } console.log( new AssignSemantics().x, // Calls the setter new DefineSemantics().x // Doesn't call the setter )
When you run
tsc
, the value ofuseDefineForClassFields
defaults tofalse
when it's not specified and thetarget
intsconfig.json
is present but earlier thanES2022
. This sort of makes sense because the class field language feature was added in ES2022, so before ES2022 class fields didn't exist (and thus TypeScript's legacy behavior is active). However, TypeScript'starget
setting currently defaults toES3
which unfortunately means that theuseDefineForClassFields
setting currently defaults to false (i.e. to "wrong"). In other words if you runtsc
with all default settings, class fields will behave incorrectly.Previously esbuild tried to do what
tsc
did. That meant esbuild's version ofuseDefineForClassFields
wasfalse
by default, and was alsofalse
if esbuild's--target=
was present but earlier thanes2022
. However, TypeScript's legacy class field behavior is becoming increasingly irrelevant and people who expect class fields in TypeScript to work like they do in JavaScript are confused when they use esbuild with default settings. It's also confusing that the behavior of class fields would change if you changed the language target (even though that's exactly how TypeScript works).So with this release, esbuild will now only use the information in
tsconfig.json
to determine whetheruseDefineForClassFields
is true or not. SpecificallyuseDefineForClassFields
will be respected if present, otherwise it will befalse
iftarget
is present intsconfig.json
and isES2021
or earlier, otherwise it will betrue
. Targets passed to esbuild's--target=
setting will no longer affectuseDefineForClassFields
.Note that this means different directories in your build can have different values for this setting since esbuild allows different directories to have different
tsconfig.json
files within the same build. This should let you migrate your code one directory at a time without esbuild's--target=
setting affecting the semantics of your code. -
Add support for
verbatimModuleSyntax
from TypeScript 5.0TypeScript 5.0 added a new option called
verbatimModuleSyntax
that deprecates and replaces two older options,preserveValueImports
andimportsNotUsedAsValues
. SettingverbatimModuleSyntax
to true intsconfig.json
tells esbuild to not drop unused import statements. Specifically esbuild now treats"verbatimModuleSyntax": true
as if you had specified both"preserveValueImports": true
and"importsNotUsedAsValues": "preserve"
. -
Add multiple inheritance for
tsconfig.json
from TypeScript 5.0TypeScript 5.0 now allows multiple inheritance for
tsconfig.json
files. You can now pass an array of filenames via theextends
parameter and yourtsconfig.json
will start off containing properties from all of those configuration files, in order. This release of esbuild adds support for this new TypeScript feature. -
Remove support for
moduleSuffixes
(#2395)The community has requested that esbuild remove support for TypeScript's
moduleSuffixes
feature, so it has been removed in this release. Instead you can use esbuild's--resolve-extensions=
feature to select which module suffix you want to build with. -
Apply
--tsconfig=
overrides tostdin
and virtual files (#385, #2543)When you override esbuild's automatic
tsconfig.json
file detection with--tsconfig=
to pass a specifictsconfig.json
file, esbuild previously didn't apply these settings to source code passed via thestdin
API option or to TypeScript files from plugins that weren't in thefile
namespace. This release changes esbuild's behavior so that settings fromtsconfig.json
also apply to these source code files as well. -
Support
--tsconfig-raw=
in build API calls (#943, #2440)Previously if you wanted to override esbuild's automatic
tsconfig.json
file detection, you had to create a newtsconfig.json
file and pass the file name to esbuild via the--tsconfig=
flag. With this release, you can now optionally use--tsconfig-raw=
instead to pass the contents oftsconfig.json
to esbuild directly instead of passing the file name. For example, you can now use--tsconfig-raw={"compilerOptions":{"experimentalDecorators":true}}
to enable TypeScript experimental decorators directly using a command-line flag (assuming you escape the quotes correctly using your current shell's quoting rules). The--tsconfig-raw=
flag previously only worked with transform API calls but with this release, it now works with build API calls too. -
Ignore all
tsconfig.json
files innode_modules
(#276, #2386)This changes esbuild's behavior that applies
tsconfig.json
to all files in the subtree of the directory containingtsconfig.json
. In version 0.12.7, esbuild started ignoringtsconfig.json
files insidenode_modules
folders. The rationale is that people typically do this by mistake and that doing this intentionally is a rare use case that doesn't need to be supported. However, this change only applied to certain syntax-specific settings (e.g.jsxFactory
) but did not apply to path resolution settings (e.g.paths
). With this release, esbuild will now ignore alltsconfig.json
files innode_modules
instead of only ignoring certain settings. -
Ignore
tsconfig.json
when resolving paths withinnode_modules
(#2481)Previously fields in
tsconfig.json
related to path resolution (e.g.paths
) were respected for all files in the subtree containing thattsconfig.json
file, even within a nestednode_modules
subdirectory. This meant that a project'spaths
settings could potentially affect any bundled packages. With this release, esbuild will no longer usetsconfig.json
settings during path resolution inside nestednode_modules
subdirectories. -
Prefer
.js
over.ts
withinnode_modules
(#3019)The default list of implicit extensions that esbuild will try appending to import paths contains
.ts
before.js
. This makes it possible to bundle TypeScript projects that reference other files in the project using extension-less imports (e.g../some-file
to load./some-file.ts
instead of./some-file.js
). However, this behavior is undesirable withinnode_modules
directories. Some package authors publish both their original TypeScript code and their compiled JavaScript code side-by-side. In these cases, esbuild should arguably be using the compiled JavaScript files instead of the original TypeScript files because the TypeScript compilation settings for files within the package should be determined by the package author, not the user of esbuild. So with this release, esbuild will now prefer implicit.js
extensions over.ts
when searching for import paths withinnode_modules
.
These changes are intended to improve esbuild's compatibility with
tsc
and reduce the number of unfortunate behaviors regardingtsconfig.json
and esbuild. -
-
Add a workaround for bugs in Safari 16.2 and earlier (#3072)
Safari's JavaScript parser had a bug (which has now been fixed) where at least something about unary/binary operators nested inside default arguments nested inside either a function or class expression was incorrectly considered a syntax error if that expression was the target of a property assignment. Here are some examples that trigger this Safari bug:
❱ x(function (y = -1) {}.z = 2) SyntaxError: Left hand side of operator '=' must be a reference. ❱ x(class { f(y = -1) {} }.z = 2) SyntaxError: Left hand side of operator '=' must be a reference.
It's not clear what the exact conditions are that trigger this bug. However, a workaround for this bug appears to be to post-process your JavaScript to wrap any in function and class declarations that are the direct target of a property access expression in parentheses. That's the workaround that UglifyJS applies for this issue: mishoo/UglifyJS#2056. So that's what esbuild now does starting with this release:
// Original code x(function (y = -1) {}.z = 2, class { f(y = -1) {} }.z = 2) // Old output (with --minify --target=safari16.2) x(function(c=-1){}.z=2,class{f(c=-1){}}.z=2); // New output (with --minify --target=safari16.2) x((function(c=-1){}).z=2,(class{f(c=-1){}}).z=2);
This fix is not enabled by default. It's only enabled when
--target=
contains Safari 16.2 or earlier, such as with--target=safari16.2
. You can also explicitly enable or disable this specific transform (calledfunction-or-class-property-access
) with--supported:function-or-class-property-access=false
. -
Fix esbuild's TypeScript type declarations to forbid unknown properties (#3089)
Version 0.17.0 of esbuild introduced a specific form of function overloads in the TypeScript type definitions for esbuild's API calls that looks like this:
interface TransformOptions { legalComments?: 'none' | 'inline' | 'eof' | 'external' } interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> { legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined) } declare function transformSync<ProvidedOptions extends TransformOptions>(input: string, options?: ProvidedOptions): TransformResult<ProvidedOptions> declare function transformSync(input: string, options?: TransformOptions): TransformResult
This more accurately reflects how esbuild's JavaScript API behaves. The result object returned by
transformSync
only has thelegalComments
property if you passlegalComments: 'external'
:// These have type "string | undefined" transformSync('').legalComments transformSync('', { legalComments: 'eof' }).legalComments // This has type "string" transformSync('', { legalComments: 'external' }).legalComments
However, this form of function overloads unfortunately allows typos (e.g.
egalComments
) to pass the type checker without generating an error as TypeScript allows all objects with unknown properties to extendTransformOptions
. These typos result in esbuild's API throwing an error at run-time.To prevent typos during type checking, esbuild's TypeScript type definitions will now use a different form that looks like this:
type SameShape<Out, In extends Out> = In & { [Key in Exclude<keyof In, keyof Out>]: never } interface TransformOptions { legalComments?: 'none' | 'inline' | 'eof' | 'external' } interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> { legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined) } declare function transformSync<T extends TransformOptions>(input: string, options?: SameShape<TransformOptions, T>): TransformResult<T>
This change should hopefully not affect correct code. It should hopefully introduce type errors only for incorrect code.
-
Fix CSS nesting transform for pseudo-elements (#3119)
This release fixes esbuild's CSS nesting transform for pseudo-elements (e.g.
::before
and::after
). The CSS nesting specification says that the nesting selector does not work with pseudo-elements. This can be seen in the example below: esbuild does not carry the parent pseudo-element::before
through the nesting selector&
. However, that doesn't apply to pseudo-elements that are within the same selector. Previously esbuild had a bug where it considered pseudo-elements in both locations as invalid. This release changes esbuild to only consider those from the parent selector invalid, which should align with the specification:/* Original code */ a, b::before { &.c, &::after { content: 'd'; } } /* Old output (with --target=chrome90) */ a:is(.c, ::after) { content: "d"; } /* New output (with --target=chrome90) */ a.c, a::after { content: "d"; }
-
Forbid
&
before a type selector in nested CSSThe people behind the work-in-progress CSS nesting specification have very recently decided to forbid nested CSS that looks like
&div
. You will have to use eitherdiv&
or&:is(div)
instead. This release of esbuild has been updated to take this new change into consideration. Doing this now generates a warning. The suggested fix is slightly different depending on where in the overall selector it happened:▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error] example.css:2:3: 2 │ &input { │ ~~~~~ ╵ :is(input) CSS nesting syntax does not allow the "&" selector to come before a type selector. You can wrap this selector in ":is()" as a workaround. This restriction exists to avoid problems with SASS nesting, where the same syntax means something very different that has no equivalent in real CSS (appending a suffix to the parent selector). ▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error] example.css:6:8: 6 │ .form &input { │ ~~~~~~ ╵ input& CSS nesting syntax does not allow the "&" selector to come before a type selector. You can move the "&" to the end of this selector as a workaround. This restriction exists to avoid problems with SASS nesting, where the same syntax means something very different that has no equivalent in real CSS (appending a suffix to the parent selector).
-
Fix CSS transform bugs with nested selectors that start with a combinator (#3096)
This release fixes several bugs regarding transforming nested CSS into non-nested CSS for older browsers. The bugs were due to lack of test coverage for nested selectors with more than one compound selector where they all start with the same combinator. Here's what some problematic cases look like before and after these fixes:
/* Original code */ .foo { > &a, > &b { color: red; } } .bar { > &a, + &b { color: green; } } /* Old output (with --target=chrome90) */ .foo :is(> .fooa, > .foob) { color: red; } .bar :is(> .bara, + .barb) { color: green; } /* New output (with --target=chrome90) */ .foo > :is(a.foo, b.foo) { color: red; } .bar > a.bar, .bar + b.bar { color: green; }
-
Fix bug with TypeScript parsing of instantiation expressions followed by
=
(#3111)This release fixes esbuild's TypeScript-to-JavaScript conversion code in the case where a potential instantiation expression is followed immediately by a
=
token (such that the trailing>
becomes a>=
token). Previously esbuild considered that to still be an instantiation expression, but the official TypeScript compiler considered it to be a>=
operator instead. This release changes esbuild's interpretation to match TypeScript. This edge case currently appears to be problematic for other TypeScript-to-JavaScript converters as well:Original code TypeScript esbuild 0.17.18 esbuild 0.17.19 Sucrase Babel x<y>=a<b<c>>()
x<y>=a();
x=a();
x<y>=a();
x=a()
Invalid left-hand side in assignment expression -
Avoid removing unrecognized directives from the directive prologue when minifying (#3115)
The directive prologue in JavaScript is a sequence of top-level string expressions that come before your code. The only directives that JavaScript engines currently recognize are
use strict
and sometimesuse asm
. However, the people behind React have made up their own directive for their own custom dialect of JavaScript. Previously esbuild only preserved theuse strict
directive when minifying, although you could still write React JavaScript with esbuild using something like--banner:js="'your directive here';"
. With this release, you can now put arbitrary directives in the entry point and esbuild will preserve them in its minified output:// Original code 'use wtf'; console.log(123) // Old output (with --minify) console.log(123); // New output (with --minify) "use wtf";console.log(123);
Note that this means esbuild will no longer remove certain stray top-level strings when minifying. This behavior is an intentional change because these stray top-level strings are actually part of the directive prologue, and could potentially have semantics assigned to them (as was the case with React).
-
Improved minification of binary shift operators
With this release, esbuild's minifier will now evaluate the
<<
and>>>
operators if the resulting code would be shorter:// Original code console.log(10 << 10, 10 << 20, -123 >>> 5, -123 >>> 10); // Old output (with --minify) console.log(10<<10,10<<20,-123>>>5,-123>>>10); // New output (with --minify) console.log(10240,10<<20,-123>>>5,4194303);
-
Fix non-default JSON import error with
export {} from
(#3070)This release fixes a bug where esbuild incorrectly identified statements of the form
export { default as x } from "y" assert { type: "json" }
as a non-default import. The bug did not affect code of the formimport { default as x } from ...
(only code that used theexport
keyword). -
Fix a crash with an invalid subpath import (#3067)
Previously esbuild could crash when attempting to generate a friendly error message for an invalid subpath import (i.e. an import starting with
#
). This happened because esbuild originally only supported theexports
field and the code for that error message was not updated when esbuild later added support for theimports
field. This crash has been fixed.
-
Fix CSS nesting transform for top-level
&
(#3052)Previously esbuild could crash with a stack overflow when lowering CSS nesting rules with a top-level
&
, such as in the code below. This happened because esbuild's CSS nesting transform didn't handle top-level&
, causing esbuild to inline the top-level selector into itself. This release handles top-level&
by replacing it with the:scope
pseudo-class:/* Original code */ &, a { .b { color: red; } } /* New output (with --target=chrome90) */ :is(:scope, a) .b { color: red; }
-
Support
exports
inpackage.json
forextends
intsconfig.json
(#3058)TypeScript 5.0 added the ability to use
extends
intsconfig.json
to reference a path in a package whosepackage.json
file contains anexports
map that points to the correct location. This doesn't automatically work in esbuild becausetsconfig.json
affects esbuild's path resolution, so esbuild's normal path resolution logic doesn't apply.This release adds support for doing this by adding some additional code that attempts to resolve the
extends
path using theexports
field. The behavior should be similar enough to esbuild's main path resolution logic to work as expected.Note that esbuild always treats this
extends
import as arequire()
import since that's what TypeScript appears to do. Specifically therequire
condition will be active and theimport
condition will be inactive. -
Fix watch mode with
NODE_PATH
(#3062)Node has a rarely-used feature where you can extend the set of directories that node searches for packages using the
NODE_PATH
environment variable. While esbuild supports this too, previously a bug prevented esbuild's watch mode from picking up changes to imported files that were contained directly in aNODE_PATH
directory. You're supposed to useNODE_PATH
for packages, but some people abuse this feature by putting files in that directory instead (e.g.node_modules/some-file.js
instead ofnode_modules/some-pkg/some-file.js
). The watch mode bug happens when you do this because esbuild first tries to readsome-file.js
as a directory and then as a file. Watch mode was incorrectly waiting forsome-file.js
to become a valid directory. This release fixes this edge case bug by changing watch mode to watchsome-file.js
as a file when this happens.
-
Fix CSS nesting transform for triple-nested rules that start with a combinator (#3046)
This release fixes a bug with esbuild where triple-nested CSS rules that start with a combinator were not transformed correctly for older browsers. Here's an example of such a case before and after this bug fix:
/* Original input */ .a { color: red; > .b { color: green; > .c { color: blue; } } } /* Old output (with --target=chrome90) */ .a { color: red; } .a > .b { color: green; } .a .b > .c { color: blue; } /* New output (with --target=chrome90) */ .a { color: red; } .a > .b { color: green; } .a > .b > .c { color: blue; }
-
Support
--inject
with a file loaded using thecopy
loader (#3041)This release now allows you to use
--inject
with a file that is loaded using thecopy
loader. Thecopy
loader copies the imported file to the output directory verbatim and rewrites the path in theimport
statement to point to the copied output file. When used with--inject
, this means the injected file will be copied to the output directory as-is and a bareimport
statement for that file will be inserted in any non-copy output files that esbuild generates.Note that since esbuild doesn't parse the contents of copied files, esbuild will not expose any of the export names as usable imports when you do this (in the way that esbuild's
--inject
feature is typically used). However, any side-effects that the injected file has will still occur.
-
Allow keywords as type parameter names in mapped types (#3033)
TypeScript allows type keywords to be used as parameter names in mapped types. Previously esbuild incorrectly treated this as an error. Code that does this is now supported:
type Foo = 'a' | 'b' | 'c' type A = { [keyof in Foo]: number } type B = { [infer in Foo]: number } type C = { [readonly in Foo]: number }
-
Add annotations for re-exported modules in node (#2486, #3029)
Node lets you import named imports from a CommonJS module using ESM import syntax. However, the allowed names aren't derived from the properties of the CommonJS module. Instead they are derived from an arbitrary syntax-only analysis of the CommonJS module's JavaScript AST.
To accommodate node doing this, esbuild's ESM-to-CommonJS conversion adds a special non-executable "annotation" for node that describes the exports that node should expose in this scenario. It takes the form
0 && (module.exports = { ... })
and comes at the end of the file (0 && expr
meansexpr
is never evaluated).Previously esbuild didn't do this for modules re-exported using the
export * from
syntax. Annotations for these re-exports will now be added starting with this release:// Original input export { foo } from './foo' export * from './bar' // Old output (with --format=cjs --platform=node) ... 0 && (module.exports = { foo }); // New output (with --format=cjs --platform=node) ... 0 && (module.exports = { foo, ...require("./bar") });
Note that you need to specify both
--format=cjs
and--platform=node
to get these node-specific annotations. -
Avoid printing an unnecessary space in between a number and a
.
(#3026)JavaScript typically requires a space in between a number token and a
.
token to avoid the.
being interpreted as a decimal point instead of a member expression. However, this space is not required if the number token itself contains a decimal point, an exponent, or uses a base other than 10. This release of esbuild now avoids printing the unnecessary space in these cases:// Original input foo(1000 .x, 0 .x, 0.1 .x, 0.0001 .x, 0xFFFF_0000_FFFF_0000 .x) // Old output (with --minify) foo(1e3 .x,0 .x,.1 .x,1e-4 .x,0xffff0000ffff0000 .x); // New output (with --minify) foo(1e3.x,0 .x,.1.x,1e-4.x,0xffff0000ffff0000.x);
-
Fix server-sent events with live reload when writing to the file system root (#3027)
This release fixes a bug where esbuild previously failed to emit server-sent events for live reload when
outdir
was the file system root, such as/
. This happened because/
is the only path on Unix that cannot have a trailing slash trimmed from it, which was fixed by improved path handling.
-
Allow the TypeScript 5.0
const
modifier in object type declarations (#3021)The new TypeScript 5.0
const
modifier was added to esbuild in version 0.17.5, and works with classes, functions, and arrow expressions. However, support for it wasn't added to object type declarations (e.g. interfaces) due to an oversight. This release adds support for these cases, so the following TypeScript 5.0 code can now be built with esbuild:interface Foo { <const T>(): T } type Bar = { new <const T>(): T }
-
Implement preliminary lowering for CSS nesting (#1945)
Chrome has implemented the new CSS nesting specification in version 112, which is currently in beta but will become stable very soon. So CSS nesting is now a part of the web platform!
This release of esbuild can now transform nested CSS syntax into non-nested CSS syntax for older browsers. The transformation relies on the
:is()
pseudo-class in many cases, so the transformation is only guaranteed to work when targeting browsers that support:is()
(e.g. Chrome 88+). You'll need to set esbuild'starget
to the browsers you intend to support to tell esbuild to do this transformation. You will get a warning if you use CSS nesting syntax with atarget
which includes older browsers that don't support:is()
.The lowering transformation looks like this:
/* Original input */ a.btn { color: #333; &:hover { color: #444 } &:active { color: #555 } } /* New output (with --target=chrome88) */ a.btn { color: #333; } a.btn:hover { color: #444; } a.btn:active { color: #555; }
More complex cases may generate the
:is()
pseudo-class:/* Original input */ div, p { .warning, .error { padding: 20px; } } /* New output (with --target=chrome88) */ :is(div, p) :is(.warning, .error) { padding: 20px; }
In addition, esbuild now has a special warning message for nested style rules that start with an identifier. This isn't allowed in CSS because the syntax would be ambiguous with the existing declaration syntax. The new warning message looks like this:
▲ [WARNING] A nested style rule cannot start with "p" because it looks like the start of a declaration [css-syntax-error] <stdin>:1:7: 1 │ main { p { margin: auto } } │ ^ ╵ :is(p) To start a nested style rule with an identifier, you need to wrap the identifier in ":is(...)" to prevent the rule from being parsed as a declaration.
Keep in mind that the transformation in this release is a preliminary implementation. CSS has many features that interact in complex ways, and there may be some edge cases that don't work correctly yet.
-
Minification now removes unnecessary
&
CSS nesting selectorsThis release introduces the following CSS minification optimizations:
/* Original input */ a { font-weight: bold; & { color: blue; } & :hover { text-decoration: underline; } } /* Old output (with --minify) */ a{font-weight:700;&{color:#00f}& :hover{text-decoration:underline}} /* New output (with --minify) */ a{font-weight:700;:hover{text-decoration:underline}color:#00f}
-
Minification now removes duplicates from CSS selector lists
This release introduces the following CSS minification optimization:
/* Original input */ div, div { color: red } /* Old output (with --minify) */ div,div{color:red} /* New output (with --minify) */ div{color:red}
-
Work around an issue with
NODE_PATH
and Go's WebAssembly internals (#3001)Go's WebAssembly implementation returns
EINVAL
instead ofENOTDIR
when using thereaddir
syscall on a file. This messes up esbuild's implementation of node's module resolution algorithm since encounteringENOTDIR
causes esbuild to continue its search (since it's a normal condition) while other encountering other errors causes esbuild to fail with an I/O error (since it's an unexpected condition). You can encounter this issue in practice if you use node's legacyNODE_PATH
feature to tell esbuild to resolve node modules in a custom directory that was not installed by npm. This release works around this problem by convertingEINVAL
intoENOTDIR
for thereaddir
syscall. -
Fix a minification bug with CSS
@layer
rules that have parsing errors (#3016)CSS at-rules require either a
{}
block or a semicolon at the end. Omitting both of these causes esbuild to treat the rule as an unknown at-rule. Previous releases of esbuild had a bug that incorrectly removed unknown at-rules without any children during minification if the at-rule token matched an at-rule that esbuild can handle. Specifically cssnano can generate@layer
rules with parsing errors, and empty@layer
rules cannot be removed because they have side effects (@layer
didn't exist when esbuild's CSS support was added, so esbuild wasn't written to handle this). This release changes esbuild to no longer discard@layer
rules with parsing errors when minifying (the rule@layer c
has a parsing error):/* Original input */ @layer a { @layer b { @layer c } } /* Old output (with --minify) */ @layer a.b; /* New output (with --minify) */ @layer a.b.c;
-
Unterminated strings in CSS are no longer an error
The CSS specification provides rules for handling parsing errors. One of those rules is that user agents must close strings upon reaching the end of a line (i.e., before an unescaped line feed, carriage return or form feed character), but then drop the construct (declaration or rule) in which the string was found. For example:
p { color: green; font-family: 'Courier New Times color: red; color: green; }
...would be treated the same as:
p { color: green; color: green; }
...because the second declaration (from
font-family
to the semicolon aftercolor: red
) is invalid and is dropped.Previously using this CSS with esbuild failed to build due to a syntax error, even though the code can be interpreted by a browser. With this release, the code now produces a warning instead of an error, and esbuild prints the invalid CSS such that it stays invalid in the output:
/* esbuild's new non-minified output: */ p { color: green; font-family: 'Courier New Times color: red; color: green; }
/* esbuild's new minified output: */ p{font-family:'Courier New Times color: red;color:green}
-
Fix a crash when parsing inline TypeScript decorators (#2991)
Previously esbuild's TypeScript parser crashed when parsing TypeScript decorators if the definition of the decorator was inlined into the decorator itself:
@(function sealed(constructor: Function) { Object.seal(constructor); Object.seal(constructor.prototype); }) class Foo {}
This crash was not noticed earlier because this edge case did not have test coverage. The crash is fixed in this release.
-
Fix the
alias
feature to always prefer the longest match (#2963)It's possible to configure conflicting aliases such as
--alias:a=b
and--alias:a/c=d
, which is ambiguous for the import patha/c/x
(since it could map to eitherb/c/x
ord/x
). Previously esbuild would pick the first matchingalias
, which would non-deterministically pick between one of the possible matches. This release fixes esbuild to always deterministically pick the longest possible match. -
Minify calls to some global primitive constructors (#2962)
With this release, esbuild's minifier now replaces calls to
Boolean
/Number
/String
/BigInt
with equivalent shorter code when relevant:// Original code console.log( Boolean(a ? (b | c) !== 0 : (c & d) !== 0), Number(e ? '1' : '2'), String(e ? '1' : '2'), BigInt(e ? 1n : 2n), ) // Old output (with --minify) console.log(Boolean(a?(b|c)!==0:(c&d)!==0),Number(e?"1":"2"),String(e?"1":"2"),BigInt(e?1n:2n)); // New output (with --minify) console.log(!!(a?b|c:c&d),+(e?"1":"2"),e?"1":"2",e?1n:2n);
-
Adjust some feature compatibility tables for node (#2940)
This release makes the following adjustments to esbuild's internal feature compatibility tables for node, which tell esbuild which versions of node are known to support all aspects of that feature:
class-private-brand-checks
: node v16.9+ => node v16.4+ (a decrease)hashbang
: node v12.0+ => node v12.5+ (an increase)optional-chain
: node v16.9+ => node v16.1+ (a decrease)template-literal
: node v4+ => node v10+ (an increase)
Each of these adjustments was identified by comparing against data from the
node-compat-table
package and was manually verified using old node executables downloaded from https://nodejs.org/download/release/.
-
Update esbuild's handling of CSS nesting to match the latest specification changes (#1945)
The syntax for the upcoming CSS nesting feature has recently changed. The
@nest
prefix that was previously required in some cases is now gone, and nested rules no longer have to start with&
(as long as they don't start with an identifier or function token).This release updates esbuild's pass-through handling of CSS nesting syntax to match the latest specification changes. So you can now use esbuild to bundle CSS containing nested rules and try them out in a browser that supports CSS nesting (which includes nightly builds of both Chrome and Safari).
However, I'm not implementing lowering of nested CSS to non-nested CSS for older browsers yet. While the syntax has been decided, the semantics are still in flux. In particular, there is still some debate about changing the fundamental way that CSS nesting works. For example, you might think that the following CSS is equivalent to a
.outer .inner button { ... }
rule:.inner button { .outer & { color: red; } }
But instead it's actually equivalent to a
.outer :is(.inner button) { ... }
rule which unintuitively also matches the following DOM structure:<div class="inner"> <div class="outer"> <button></button> </div> </div>
The
:is()
behavior is preferred by browser implementers because it's more memory-efficient, but the straightforward translation into a.outer .inner button { ... }
rule is preferred by developers used to the existing CSS preprocessing ecosystem (e.g. SASS). It seems premature to commit esbuild to specific semantics for this syntax at this time given the ongoing debate. -
Fix cross-file CSS rule deduplication involving
url()
tokens (#2936)Previously cross-file CSS rule deduplication didn't handle
url()
tokens correctly. These tokens contain references to import paths which may be internal (i.e. in the bundle) or external (i.e. not in the bundle). When comparing twourl()
tokens for equality, the underlying import paths should be compared instead of their references. This release of esbuild fixesurl()
token comparisons. One side effect is that@font-face
rules should now be deduplicated correctly across files:/* Original code */ @import "data:text/css, \ @import 'http://example.com/style.css'; \ @font-face { src: url(http://example.com/font.ttf) }"; @import "data:text/css, \ @font-face { src: url(http://example.com/font.ttf) }"; /* Old output (with --bundle --minify) */ @import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}@font-face{src:url(http://example.com/font.ttf)} /* New output (with --bundle --minify) */ @import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}
-
Parse rest bindings in TypeScript types (#2937)
Previously esbuild was unable to parse the following valid TypeScript code:
let tuple: (...[e1, e2, ...es]: any) => any
This release includes support for parsing code like this.
-
Fix TypeScript code translation for certain computed
declare
class fields (#2914)In TypeScript, the key of a computed
declare
class field should only be preserved if there are no decorators for that field. Previously esbuild always preserved the key, but esbuild will now remove the key to match the output of the TypeScript compiler:// Original code declare function dec(a: any, b: any): any declare const removeMe: unique symbol declare const keepMe: unique symbol class X { declare [removeMe]: any @dec declare [keepMe]: any } // Old output var _a; class X { } removeMe, _a = keepMe; __decorateClass([ dec ], X.prototype, _a, 2); // New output var _a; class X { } _a = keepMe; __decorateClass([ dec ], X.prototype, _a, 2);
-
Fix a crash with path resolution error generation (#2913)
In certain situations, a module containing an invalid import path could previously cause esbuild to crash when it attempts to generate a more helpful error message. This crash has been fixed.
-
Fix a minification bug with non-ASCII identifiers (#2910)
This release fixes a bug with esbuild where non-ASCII identifiers followed by a keyword were incorrectly not separated by a space. This bug affected both the
in
andinstanceof
keywords. Here's an example of the fix:// Original code π in a // Old output (with --minify --charset=utf8) πin a; // New output (with --minify --charset=utf8) π in a;
-
Fix a regression with esbuild's WebAssembly API in version 0.17.6 (#2911)
Version 0.17.6 of esbuild updated the Go toolchain to version 1.20.0. This had the unfortunate side effect of increasing the amount of stack space that esbuild uses (presumably due to some changes to Go's WebAssembly implementation) which could cause esbuild's WebAssembly-based API to crash with a stack overflow in cases where it previously didn't crash. One such case is the package
grapheme-splitter
which contains code that looks like this:if ( (0x0300 <= code && code <= 0x036F) || (0x0483 <= code && code <= 0x0487) || (0x0488 <= code && code <= 0x0489) || (0x0591 <= code && code <= 0x05BD) || // ... many hundreds of lines later ... ) { return; }
This edge case involves a chain of binary operators that results in an AST over 400 nodes deep. Normally this wouldn't be a problem because Go has growable call stacks, so the call stack would just grow to be as large as needed. However, WebAssembly byte code deliberately doesn't expose the ability to manipulate the stack pointer, so Go's WebAssembly translation is forced to use the fixed-size WebAssembly call stack. So esbuild's WebAssembly implementation is vulnerable to stack overflow in cases like these.
It's not unreasonable for this to cause a stack overflow, and for esbuild's answer to this problem to be "don't write code like this." That's how many other AST-manipulation tools handle this problem. However, it's possible to implement AST traversal using iteration instead of recursion to work around limited call stack space. This version of esbuild implements this code transformation for esbuild's JavaScript parser and printer, so esbuild's WebAssembly implementation is now able to process the
grapheme-splitter
package (at least when compiled with Go 1.20.0 and run with node's WebAssembly implementation).
-
Change esbuild's parsing of TypeScript instantiation expressions to match TypeScript 4.8+ (#2907)
This release updates esbuild's implementation of instantiation expression erasure to match microsoft/TypeScript#49353. The new rules are as follows (copied from TypeScript's PR description):
When a potential type argument list is followed by
- a line break,
- an
(
token, - a template literal string, or
- any token except
<
or>
that isn't the start of an expression,
we consider that construct to be a type argument list. Otherwise we consider the construct to be a
<
relational expression followed by a>
relational expression. -
Ignore
sideEffects: false
for imported CSS files (#1370, #1458, #2905)This release ignores the
sideEffects
annotation inpackage.json
for CSS files that are imported into JS files using esbuild'scss
loader. This means that these CSS files are no longer be tree-shaken.Importing CSS into JS causes esbuild to automatically create a CSS entry point next to the JS entry point containing the bundled CSS. Previously packages that specified some form of
"sideEffects": false
could potentially cause esbuild to consider one or more of the JS files on the import path to the CSS file to be side-effect free, which would result in esbuild removing that CSS file from the bundle. This was problematic because the removal of that CSS is outwardly observable, since all CSS is global, so it was incorrect for previous versions of esbuild to tree-shake CSS files imported into JS files. -
Add constant folding for certain additional equality cases (#2394, #2895)
This release adds constant folding for expressions similar to the following:
// Original input console.log( null === 'foo', null === undefined, null == undefined, false === 0, false == 0, 1 === true, 1 == true, ) // Old output console.log( null === "foo", null === void 0, null == void 0, false === 0, false == 0, 1 === true, 1 == true ); // New output console.log( false, false, true, false, true, false, true );
-
Fix a CSS parser crash on invalid CSS (#2892)
Previously the following invalid CSS caused esbuild's parser to crash:
@media screen
The crash was caused by trying to construct a helpful error message assuming that there was an opening
{
token, which is not the case here. This release fixes the crash. -
Inline TypeScript enums that are referenced before their declaration
Previously esbuild inlined enums within a TypeScript file from top to bottom, which meant that references to TypeScript enum members were only inlined within the same file if they came after the enum declaration. With this release, esbuild will now inline enums even when they are referenced before they are declared:
// Original input export const foo = () => Foo.FOO const enum Foo { FOO = 0 } // Old output (with --tree-shaking=true) export const foo = () => Foo.FOO; var Foo = /* @__PURE__ */ ((Foo2) => { Foo2[Foo2["FOO"] = 0] = "FOO"; return Foo2; })(Foo || {}); // New output (with --tree-shaking=true) export const foo = () => 0 /* FOO */;
This makes esbuild's TypeScript output smaller and faster when processing code that does this. I noticed this issue when I ran the TypeScript compiler's source code through esbuild's bundler. Now that the TypeScript compiler is going to be bundled with esbuild in the upcoming TypeScript 5.0 release, improvements like this will also improve the TypeScript compiler itself!
-
Fix esbuild installation on Arch Linux (#2785, #2812, #2865)
Someone made an unofficial
esbuild
package for Linux that adds theESBUILD_BINARY_PATH=/usr/bin/esbuild
environment variable to the user's default environment. This breaks all npm installations of esbuild for users with this unofficial Linux package installed, which has affected many people. Most (all?) people who encounter this problem haven't even installed this unofficial package themselves; instead it was installed for them as a dependency of another Linux package. The problematic change to add theESBUILD_BINARY_PATH
environment variable was reverted in the latest version of this unofficial package. However, old versions of this unofficial package are still there and will be around forever. With this release,ESBUILD_BINARY_PATH
is now ignored by esbuild's install script when it's set to the value/usr/bin/esbuild
. This should unbreak using npm to installesbuild
in these problematic Linux environments.Note: The
ESBUILD_BINARY_PATH
variable is an undocumented way to override the location of esbuild's binary when esbuild's npm package is installed, which is necessary to substitute your own locally-built esbuild binary when debugging esbuild's npm package. It's only meant for very custom situations and should absolutely not be forced on others by default, especially without their knowledge. I may remove the code in esbuild's installer that readsESBUILD_BINARY_PATH
in the future to prevent these kinds of issues. It will unfortunately make debugging esbuild harder. IfESBUILD_BINARY_PATH
is ever removed, it will be done in a "breaking change" release.
-
Parse
const
type parameters from TypeScript 5.0The TypeScript 5.0 beta announcement adds
const
type parameters to the language. You can now add theconst
modifier on a type parameter of a function, method, or class like this:type HasNames = { names: readonly string[] }; const getNamesExactly = <const T extends HasNames>(arg: T): T["names"] => arg.names; const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] });
The type of
names
in the above example isreadonly ["Alice", "Bob", "Eve"]
. Marking the type parameter asconst
behaves as if you had writtenas const
at every use instead. The above code is equivalent to the following TypeScript, which was the only option before TypeScript 5.0:type HasNames = { names: readonly string[] }; const getNamesExactly = <T extends HasNames>(arg: T): T["names"] => arg.names; const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] } as const);
You can read the announcement for more information.
-
Make parsing generic
async
arrow functions more strict in.tsx
filesPreviously esbuild's TypeScript parser incorrectly accepted the following code as valid:
let fn = async <T> () => {};
The official TypeScript parser rejects this code because it thinks it's the identifier
async
followed by a JSX element starting with<T>
. So with this release, esbuild will now reject this syntax in.tsx
files too. You'll now have to add a comma after the type parameter to get generic arrow functions like this to parse in.tsx
files:let fn = async <T,> () => {};
-
Allow the
in
andout
type parameter modifiers on class expressionsTypeScript 4.7 added the
in
andout
modifiers on the type parameters of classes, interfaces, and type aliases. However, while TypeScript supported them on both class expressions and class statements, previously esbuild only supported them on class statements due to an oversight. This release now allows these modifiers on class expressions too:declare let Foo: any; Foo = class <in T> { }; Foo = class <out T> { };
-
Update
enum
constant folding for TypeScript 5.0TypeScript 5.0 contains an updated definition of what it considers a constant expression:
An expression is considered a constant expression if it is
- a number or string literal,
- a unary
+
,-
, or~
applied to a numeric constant expression, - a binary
+
,-
,*
,/
,%
,**
,<<
,>>
,>>>
,|
,&
,^
applied to two numeric constant expressions, - a binary
+
applied to two constant expressions whereof at least one is a string, - a template expression where each substitution expression is a constant expression,
- a parenthesized constant expression,
- a dotted name (e.g.
x.y.z
) that references aconst
variable with a constant expression initializer and no type annotation, - a dotted name that references an enum member with an enum literal type, or
- a dotted name indexed by a string literal (e.g.
x.y["z"]
) that references an enum member with an enum literal type.
This impacts esbuild's implementation of TypeScript's
const enum
feature. With this release, esbuild will now attempt to follow these new rules. For example, you can now initialize anenum
member with a template literal expression that contains a numeric constant:// Original input const enum Example { COUNT = 100, ERROR = `Expected ${COUNT} items`, } console.log( Example.COUNT, Example.ERROR, ) // Old output (with --tree-shaking=true) var Example = /* @__PURE__ */ ((Example2) => { Example2[Example2["COUNT"] = 100] = "COUNT"; Example2[Example2["ERROR"] = `Expected ${100 /* COUNT */} items`] = "ERROR"; return Example2; })(Example || {}); console.log( 100 /* COUNT */, Example.ERROR ); // New output (with --tree-shaking=true) console.log( 100 /* COUNT */, "Expected 100 items" /* ERROR */ );
These rules are not followed exactly due to esbuild's limitations. The rule about dotted references to
const
variables is not followed both because esbuild's enum processing is done in an isolated module setting and because doing so would potentially require esbuild to use a type system, which it doesn't have. For example:// The TypeScript compiler inlines this but esbuild doesn't: declare const x = 'foo' const enum Foo { X = x } console.log(Foo.X)
Also, the rule that requires converting numbers to a string currently only followed for 32-bit signed integers and non-finite numbers. This is done to avoid accidentally introducing a bug if esbuild's number-to-string operation doesn't exactly match the behavior of a real JavaScript VM. Currently esbuild's number-to-string constant folding is conservative for safety.
-
Forbid definite assignment assertion operators on class methods
In TypeScript, class methods can use the
?
optional property operator but not the!
definite assignment assertion operator (while class fields can use both):class Foo { // These are valid TypeScript a? b! x?() {} // This is invalid TypeScript y!() {} }
Previously esbuild incorrectly allowed the definite assignment assertion operator with class methods. This will no longer be allowed starting with this release.
-
Implement HTTP
HEAD
requests in serve mode (#2851)Previously esbuild's serve mode only responded to HTTP
GET
requests. With this release, esbuild's serve mode will also respond to HTTPHEAD
requests, which are just like HTTPGET
requests except that the body of the response is omitted. -
Permit top-level await in dead code branches (#2853)
Adding top-level await to a file has a few consequences with esbuild:
- It causes esbuild to assume that the input module format is ESM, since top-level await is only syntactically valid in ESM. That prevents you from using
module
andexports
for exports and also enables strict mode, which disables certain syntax and changes how function hoisting works (among other things). - This will cause esbuild to fail the build if either top-level await isn't supported by your language target (e.g. it's not supported in ES2021) or if top-level await isn't supported by the chosen output format (e.g. it's not supported with CommonJS).
- Doing this will prevent you from using
require()
on this file or on any file that imports this file (even indirectly), since therequire()
function doesn't return a promise and so can't represent top-level await.
This release relaxes these rules slightly: rules 2 and 3 will now no longer apply when esbuild has identified the code branch as dead code, such as when it's behind an
if (false)
check. This should make it possible to use esbuild to convert code into different output formats that only uses top-level await conditionally. This release does not relax rule 1. Top-level await will still cause esbuild to unconditionally consider the input module format to be ESM, even when the top-levelawait
is in a dead code branch. This is necessary because whether the input format is ESM or not affects the whole file, not just the dead code branch. - It causes esbuild to assume that the input module format is ESM, since top-level await is only syntactically valid in ESM. That prevents you from using
-
Fix entry points where the entire file name is the extension (#2861)
Previously if you passed esbuild an entry point where the file extension is the entire file name, esbuild would use the parent directory name to derive the name of the output file. For example, if you passed esbuild a file
./src/.ts
then the output name would besrc.js
. This bug happened because esbuild first strips the file extension to get./src/
and then joins the path with the working directory to get the absolute path (e.g.join("/working/dir", "./src/")
gives/working/dir/src
). However, the join operation also canonicalizes the path which strips the trailing/
. Later esbuild uses the "base name" operation to extract the name of the output file. Since there is no trailing/
, esbuild returns"src"
as the base name instead of""
, which causes esbuild to incorrectly include the directory name in the output file name. This release fixes this bug by deferring the stripping of the file extension until after all path manipulations have been completed. So now the file./src/.ts
will generate an output file named.js
. -
Support replacing property access expressions with inject
At a high level, this change means the
inject
feature can now replace all of the same kinds of names as thedefine
feature. Soinject
is basically now a more powerful version ofdefine
, instead of previously only being able to do some of the things thatdefine
could do.Soem background is necessary to understand this change if you aren't already familiar with the
inject
feature. Theinject
feature lets you replace references to global variable with a shim. It works like this:- Put the shim in its own file
- Export the shim as the name of the global variable you intend to replace
- Pass the file to esbuild using the
inject
feature
For example, if you inject the following file using
--inject:./injected.js
:// injected.js let processShim = { cwd: () => '/' } export { processShim as process }
Then esbuild will replace all references to
process
with theprocessShim
variable, which will causeprocess.cwd()
to return'/'
. This feature is sort of abusing the ESM export alias syntax to specify the mapping of global variables to shims. But esbuild works this way because using this syntax for that purpose is convenient and terse.However, if you wanted to replace a property access expression, the process was more complicated and not as nice. You would have to:
- Put the shim in its own file
- Export the shim as some random name
- Pass the file to esbuild using the
inject
feature - Use esbuild's
define
feature to map the property access expression to the random name you made in step 2
For example, if you inject the following file using
--inject:./injected2.js --define:process.cwd=someRandomName
:// injected2.js let cwdShim = () => '/' export { cwdShim as someRandomName }
Then esbuild will replace all references to
process.cwd
with thecwdShim
variable, which will also causeprocess.cwd()
to return'/'
(but which this time will not mess with other references toprocess
, which might be desirable).With this release, using the inject feature to replace a property access expression is now as simple as using it to replace an identifier. You can now use JavaScript's "arbitrary module namespace identifier names" feature to specify the property access expression directly using a string literal. For example, if you inject the following file using
--inject:./injected3.js
:// injected3.js let cwdShim = () => '/' export { cwdShim as 'process.cwd' }
Then esbuild will now replace all references to
process.cwd
with thecwdShim
variable, which will also causeprocess.cwd()
to return'/'
(but which will also not mess with other references toprocess
).In addition to inserting a shim for a global variable that doesn't exist, another use case is replacing references to static methods on global objects with cached versions to both minify them better and to make access to them potentially faster. For example:
// Injected file let cachedMin = Math.min let cachedMax = Math.max export { cachedMin as 'Math.min', cachedMax as 'Math.max', } // Original input function clampRGB(r, g, b) { return { r: Math.max(0, Math.min(1, r)), g: Math.max(0, Math.min(1, g)), b: Math.max(0, Math.min(1, b)), } } // Old output (with --minify) function clampRGB(a,t,m){return{r:Math.max(0,Math.min(1,a)),g:Math.max(0,Math.min(1,t)),b:Math.max(0,Math.min(1,m))}} // New output (with --minify) var a=Math.min,t=Math.max;function clampRGB(h,M,m){return{r:t(0,a(1,h)),g:t(0,a(1,M)),b:t(0,a(1,m))}}
-
Fix incorrect CSS minification for certain rules (#2838)
Certain rules such as
@media
could previously be minified incorrectly. Due to a typo in the duplicate rule checker, two known@
-rules that share the same hash code were incorrectly considered to be equal. This problem was made worse by the rule hashing code considering two unknown declarations (such as CSS variables) to have the same hash code, which also isn't optimal from a performance perspective. Both of these issues have been fixed:/* Original input */ @media (prefers-color-scheme: dark) { body { --VAR-1: #000; } } @media (prefers-color-scheme: dark) { body { --VAR-2: #000; } } /* Old output (with --minify) */ @media (prefers-color-scheme: dark){body{--VAR-2: #000}} /* New output (with --minify) */ @media (prefers-color-scheme: dark){body{--VAR-1: #000}}@media (prefers-color-scheme: dark){body{--VAR-2: #000}}
-
Add
onDispose
to the plugin API (#2140, #2205)If your plugin wants to perform some cleanup after it's no longer going to be used, you can now use the
onDispose
API to register a callback for cleanup-related tasks. For example, if a plugin starts a long-running child process then it may want to terminate that process when the plugin is discarded. Previously there was no way to do this. Here's an example:let examplePlugin = { name: 'example', setup(build) { build.onDispose(() => { console.log('This plugin is no longer used') }) }, }
These
onDispose
callbacks will be called after everybuild()
call regardless of whether the build failed or not as well as after the firstdispose()
call on a given build context.
-
Make it possible to cancel a build (#2725)
The context object introduced in version 0.17.0 has a new
cancel()
method. You can use it to cancel a long-running build so that you can start a new one without needing to wait for the previous one to finish. When this happens, the previous build should always have at least one error and have no output files (i.e. it will be a failed build).Using it might look something like this:
-
JS:
let ctx = await esbuild.context({ // ... }) let rebuildWithTimeLimit = timeLimit => { let timeout = setTimeout(() => ctx.cancel(), timeLimit) return ctx.rebuild().finally(() => clearTimeout(timeout)) } let build = await rebuildWithTimeLimit(500)
-
Go:
ctx, err := api.Context(api.BuildOptions{ // ... }) if err != nil { return } rebuildWithTimeLimit := func(timeLimit time.Duration) api.BuildResult { t := time.NewTimer(timeLimit) go func() { <-t.C ctx.Cancel() }() result := ctx.Rebuild() t.Stop() return result } build := rebuildWithTimeLimit(500 * time.Millisecond)
This API is a quick implementation and isn't maximally efficient, so the build may continue to do some work for a little bit before stopping. For example, I have added stop points between each top-level phase of the bundler and in the main module graph traversal loop, but I haven't added fine-grained stop points within the internals of the linker. How quickly esbuild stops can be improved in future releases. This means you'll want to wait for
cancel()
and/or the previousrebuild()
to finish (i.e. await the returned promise in JavaScript) before starting a new build, otherwiserebuild()
will give you the just-canceled build that still hasn't ended yet. Note thatonEnd
callbacks will still be run regardless of whether or not the build was canceled. -
-
Fix server-sent events without
servedir
(#2827)The server-sent events for live reload were incorrectly using
servedir
to calculate the path to modified output files. This means events couldn't be sent whenservedir
wasn't specified. This release uses the internal output directory (which is always present) instead ofservedir
(which might be omitted), so live reload should now work whenservedir
is not specified. -
Custom entry point output paths now work with the
copy
loader (#2828)Entry points can optionally provide custom output paths to change the path of the generated output file. For example,
esbuild foo=abc.js bar=xyz.js --outdir=out
generates the filesout/foo.js
andout/bar.js
. However, this previously didn't work when using thecopy
loader due to an oversight. This bug has been fixed. For example, you can now doesbuild foo=abc.html bar=xyz.html --outdir=out --loader:.html=copy
to generate the filesout/foo.html
andout/bar.html
. -
The JS API can now take an array of objects (#2828)
Previously it was not possible to specify two entry points with the same custom output path using the JS API, although it was possible to do this with the Go API and the CLI. This will not cause a collision if both entry points use different extensions (e.g. if one uses
.js
and the other uses.css
). You can now pass the JS API an array of objects to work around this API limitation:// The previous API didn't let you specify duplicate output paths let result = await esbuild.build({ entryPoints: { // This object literal contains a duplicate key, so one is ignored 'dist': 'foo.js', 'dist': 'bar.css', }, }) // You can now specify duplicate output paths as an array of objects let result = await esbuild.build({ entryPoints: [ { in: 'foo.js', out: 'dist' }, { in: 'bar.css', out: 'dist' }, ], })
This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild
in your package.json
file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.16.0
or ~0.16.0
. See npm's documentation about semver for more information.
At a high level, the breaking changes in this release fix some long-standing issues with the design of esbuild's incremental, watch, and serve APIs. This release also introduces some exciting new features such as live reloading. In detail:
-
Move everything related to incremental builds to a new
context
API (#1037, #1606, #2280, #2418)This change removes the
incremental
andwatch
options as well as theserve()
method, and introduces a newcontext()
method. The context method takes the same arguments as thebuild()
method but only validates its arguments and does not do an initial build. Instead, builds can be triggered using therebuild()
,watch()
, andserve()
methods on the returned context object. The new context API looks like this:// Create a context for incremental builds const context = await esbuild.context({ entryPoints: ['app.ts'], bundle: true, }) // Manually do an incremental build const result = await context.rebuild() // Enable watch mode await context.watch() // Enable serve mode await context.serve() // Dispose of the context context.dispose()
The switch to the context API solves a major issue with the previous API which is that if the initial build fails, a promise is thrown in JavaScript which prevents you from accessing the returned result object. That prevented you from setting up long-running operations such as watch mode when the initial build contained errors. It also makes tearing down incremental builds simpler as there is now a single way to do it instead of three separate ways.
In addition, this release also makes some subtle changes to how incremental builds work. Previously every call to
rebuild()
started a new build. If you weren't careful, then builds could actually overlap. This doesn't cause any problems with esbuild itself, but could potentially cause problems with plugins (esbuild doesn't even give you a way to identify which overlapping build a given plugin callback is running on). Overlapping builds also arguably aren't useful, or at least aren't useful enough to justify the confusion and complexity that they bring. With this release, there is now only ever a single active build per context. Callingrebuild()
before the previous rebuild has finished now "merges" with the existing rebuild instead of starting a new build. -
Allow using
watch
andserve
together (#805, #1650, #2576)Previously it was not possible to use watch mode and serve mode together. The rationale was that watch mode is one way of automatically rebuilding your project and serve mode is another (since serve mode automatically rebuilds on every request). However, people want to combine these two features to make "live reloading" where the browser automatically reloads the page when files are changed on the file system.
This release now allows you to use these two features together. You can only call the
watch()
andserve()
APIs once each per context, but if you call them together on the same context then esbuild will automatically rebuild both when files on the file system are changed and when the server serves a request. -
Support "live reloading" through server-sent events (#802)
Server-sent events are a simple way to pass one-directional messages asynchronously from the server to the client. Serve mode now provides a
/esbuild
endpoint with anchange
event that triggers every time esbuild's output changes. So you can now implement simple "live reloading" (i.e. reloading the page when a file is edited and saved) like this:new EventSource('/esbuild').addEventListener('change', () => location.reload())
The event payload is a JSON object with the following shape:
interface ChangeEvent { added: string[] removed: string[] updated: string[] }
This JSON should also enable more complex live reloading scenarios. For example, the following code hot-swaps changed CSS
<link>
tags in place without reloading the page (but still reloads when there are other types of changes):new EventSource('/esbuild').addEventListener('change', e => { const { added, removed, updated } = JSON.parse(e.data) if (!added.length && !removed.length && updated.length === 1) { for (const link of document.getElementsByTagName("link")) { const url = new URL(link.href) if (url.host === location.host && url.pathname === updated[0]) { const next = link.cloneNode() next.href = updated[0] + '?' + Math.random().toString(36).slice(2) next.onload = () => link.remove() link.parentNode.insertBefore(next, link.nextSibling) return } } } location.reload() })
Implementing live reloading like this has a few known caveats:
-
These events only trigger when esbuild's output changes. They do not trigger when files unrelated to the build being watched are changed. If your HTML file references other files that esbuild doesn't know about and those files are changed, you can either manually reload the page or you can implement your own live reloading infrastructure instead of using esbuild's built-in behavior.
-
The
EventSource
API is supposed to automatically reconnect for you. However, there's a bug in Firefox that breaks this if the server is ever temporarily unreachable: https://bugzilla.mozilla.org/show_bug.cgi?id=1809332. Workarounds are to use any other browser, to manually reload the page if this happens, or to write more complicated code that manually closes and re-creates theEventSource
object if there is a connection error. I'm hopeful that this bug will be fixed. -
Browser vendors have decided to not implement HTTP/2 without TLS. This means that each
/esbuild
event source will take up one of your precious 6 simultaneous per-domain HTTP/1.1 connections. So if you open more than six HTTP tabs that use this live-reloading technique, you will be unable to use live reloading in some of those tabs (and other things will likely also break). The workaround is to enable HTTPS, which is now possible to do in esbuild itself (see below).
-
-
Add built-in support for HTTPS (#2169)
You can now tell esbuild's built-in development server to use HTTPS instead of HTTP. This is sometimes necessary because browser vendors have started making modern web features unavailable to HTTP websites. Previously you had to put a proxy in front of esbuild to enable HTTPS since esbuild's development server only supported HTTP. But with this release, you can now enable HTTPS with esbuild without an additional proxy.
To enable HTTPS with esbuild:
-
Generate a self-signed certificate. There are many ways to do this. Here's one way, assuming you have
openssl
installed:openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 9999 -nodes -subj /CN=127.0.0.1
-
Add
--keyfile=key.pem
and--certfile=cert.pem
to your esbuild development server command -
Click past the scary warning in your browser when you load your page
If you have more complex needs than this, you can still put a proxy in front of esbuild and use that for HTTPS instead. Note that if you see the message "Client sent an HTTP request to an HTTPS server" when you load your page, then you are using the incorrect protocol. Replace
http://
withhttps://
in your browser's URL bar.Keep in mind that esbuild's HTTPS support has nothing to do with security. The only reason esbuild now supports HTTPS is because browsers have made it impossible to do local development with certain modern web features without jumping through these extra hoops. Please do not use esbuild's development server for anything that needs to be secure. It's only intended for local development and no considerations have been made for production environments whatsoever.
-
-
Better support copying
index.html
into the output directory (#621, #1771)Right now esbuild only supports JavaScript and CSS as first-class content types. Previously this meant that if you were building a website with a HTML file, a JavaScript file, and a CSS file, you could use esbuild to build the JavaScript file and the CSS file into the output directory but not to copy the HTML file into the output directory. You needed a separate
cp
command for that.Or so I thought. It turns out that the
copy
loader added in version 0.14.44 of esbuild is sufficient to have esbuild copy the HTML file into the output directory as well. You can add something likeindex.html --loader:.html=copy
and esbuild will copyindex.html
into the output directory for you. The benefits of this are a) you don't need a separatecp
command and b) theindex.html
file will automatically be re-copied when esbuild is in watch mode and the contents ofindex.html
are edited. This also goes for other non-HTML file types that you might want to copy.This pretty much already worked. The one thing that didn't work was that esbuild's built-in development server previously only supported implicitly loading
index.html
(e.g. loading/about/index.html
when you visit/about/
) whenindex.html
existed on the file system. Previously esbuild didn't support implicitly loadingindex.html
if it was a build result. That bug has been fixed with this release so it should now be practical to use thecopy
loader to do this. -
Fix
onEnd
not being called in serve mode (#1384)Previous releases had a bug where plugin
onEnd
callbacks weren't called when using the top-levelserve()
API. This API no longer exists and the internals have been reimplemented such thatonEnd
callbacks should now always be called at the end of every build. -
Incremental builds now write out build results differently (#2104)
Previously build results were always written out after every build. However, this could cause the output directory to fill up with files from old builds if code splitting was enabled, since the file names for code splitting chunks contain content hashes and old files were not deleted.
With this release, incremental builds in esbuild will now delete old output files from previous builds that are no longer relevant. Subsequent incremental builds will also no longer overwrite output files whose contents haven't changed since the previous incremental build.
-
The
onRebuild
watch mode callback was removed (#980, #2499)Previously watch mode accepted an
onRebuild
callback which was called whenever watch mode rebuilt something. This was not great in practice because if you are running code after a build, you likely want that code to run after every build, not just after the second and subsequent builds. This release removes option to provide anonRebuild
callback. You can create a plugin with anonEnd
callback instead. TheonEnd
plugin API already exists, and is a way to run some code after every build. -
You can now return errors from
onEnd
(#2625)It's now possible to add additional build errors and/or warnings to the current build from within your
onEnd
callback by returning them in an array. This is identical to how theonStart
callback already works. The evaluation ofonEnd
callbacks have been moved around a bit internally to make this possible.Note that the build will only fail (i.e. reject the promise) if the additional errors are returned from
onEnd
. Adding additional errors to the result object that's passed toonEnd
won't affect esbuild's behavior at all. -
Print URLs and ports from the Go and JS APIs (#2393)
Previously esbuild's CLI printed out something like this when serve mode is active:
> Local: http://127.0.0.1:8000/ > Network: http://192.168.0.1:8000/
The CLI still does this, but now the JS and Go serve mode APIs will do this too. This only happens when the log level is set to
verbose
,debug
, orinfo
but not when it's set towarning
,error
, orsilent
.
-
Rebuild (a.k.a. incremental build):
Before:
const result = await esbuild.build({ ...buildOptions, incremental: true }); builds.push(result); for (let i = 0; i < 4; i++) builds.push(await result.rebuild()); await result.rebuild.dispose(); // To free resources
After:
const ctx = await esbuild.context(buildOptions); for (let i = 0; i < 5; i++) builds.push(await ctx.rebuild()); await ctx.dispose(); // To free resources
Previously the first build was done differently than subsequent builds. Now both the first build and subsequent builds are done using the same API.
-
Serve:
Before:
const serveResult = await esbuild.serve(serveOptions, buildOptions); ... serveResult.stop(); await serveResult.wait; // To free resources
After:
const ctx = await esbuild.context(buildOptions); const serveResult = await ctx.serve(serveOptions); ... await ctx.dispose(); // To free resources
-
Watch:
Before:
const result = await esbuild.build({ ...buildOptions, watch: true }); ... result.stop(); // To free resources
After:
const ctx = await esbuild.context(buildOptions); await ctx.watch(); ... await ctx.dispose(); // To free resources
-
Watch with
onRebuild
:Before:
const onRebuild = (error, result) => { if (error) console.log('subsequent build:', error); else console.log('subsequent build:', result); }; try { const result = await esbuild.build({ ...buildOptions, watch: { onRebuild } }); console.log('first build:', result); ... result.stop(); // To free resources } catch (error) { console.log('first build:', error); }
After:
const plugins = [{ name: 'my-plugin', setup(build) { let count = 0; build.onEnd(result => { if (count++ === 0) console.log('first build:', result); else console.log('subsequent build:', result); }); }, }]; const ctx = await esbuild.context({ ...buildOptions, plugins }); await ctx.watch(); ... await ctx.dispose(); // To free resources
The
onRebuild
function has now been removed. The replacement is to make a plugin with anonEnd
callback.Previously
onRebuild
did not fire for the first build (only for subsequent builds). This was usually problematic, so usingonEnd
instead ofonRebuild
is likely less error-prone. But if you need to emulate the old behavior ofonRebuild
that ignores the first build, then you'll need to manually count and ignore the first build in your plugin (as demonstrated above).
Notice how all of these API calls are now done off the new context object. You should now be able to use all three kinds of incremental builds (rebuild
, serve
, and watch
) together on the same context object. Also notice how calling dispose
on the context is now the common way to discard the context and free resources in all of these situations.
-
Fix additional comment-related regressions (#2814)
This release fixes more edge cases where the new comment preservation behavior that was added in 0.16.14 could introduce syntax errors. Specifically:
x = () => (/* comment */ {}) for ((/* comment */ let).x of y) ; function *f() { yield (/* comment */class {}) }
These cases caused esbuild to generate code with a syntax error in version 0.16.14 or above. These bugs have now been fixed.
-
Fix a regression caused by comment preservation (#2805)
The new comment preservation behavior that was added in 0.16.14 introduced a regression where comments in certain locations could cause esbuild to omit certain necessary parentheses in the output. The outermost parentheses were incorrectly removed for the following syntax forms, which then introduced syntax errors:
(/* comment */ { x: 0 }).x; (/* comment */ function () { })(); (/* comment */ class { }).prototype;
This regression has been fixed.
-
Add
format
to input files in the JSON metafile dataWhen
--metafile
is enabled, input files may now have an additionalformat
field that indicates the export format used by this file. When present, the value will either becjs
for CommonJS-style exports oresm
for ESM-style exports. This can be useful in bundle analysis.For example, esbuild's new Bundle Size Analyzer now uses this information to visualize whether ESM or CommonJS was used for each directory and file of source code (click on the CJS/ESM bar at the top).
This information is helpful when trying to reduce the size of your bundle. Using the ESM variant of a dependency instead of the CommonJS variant always results in a faster and smaller bundle because it omits CommonJS wrappers, and also may result in better tree-shaking as it allows esbuild to perform tree-shaking at the statement level instead of the module level.
-
Fix a bundling edge case with dynamic import (#2793)
This release fixes a bug where esbuild's bundler could produce incorrect output. The problematic edge case involves the entry point importing itself using a dynamic
import()
expression in an imported file, like this:// src/a.js export const A = 42; // src/b.js export const B = async () => (await import(".")).A // src/index.js export * from "./a" export * from "./b"
-
Remove new type syntax from type declarations in the
esbuild
package (#2798)Previously you needed to use TypeScript 4.3 or newer when using the
esbuild
package from TypeScript code due to the use of a getter in an interface innode_modules/esbuild/lib/main.d.ts
. This release removes this newer syntax to allow people with versions of TypeScript as far back as TypeScript 3.5 to use this latest version of theesbuild
package. Here is change that was made to esbuild's type declarations:export interface OutputFile { /** "text" as bytes */ contents: Uint8Array; /** "contents" as text (changes automatically with "contents") */ - get text(): string; + readonly text: string; }
-
Preserve some comments in expressions (#2721)
Various tools give semantic meaning to comments embedded inside of expressions. For example, Webpack and Vite have special "magic comments" that can be used to affect code splitting behavior:
import(/* webpackChunkName: "foo" */ '../foo'); import(/* @vite-ignore */ dynamicVar); new Worker(/* webpackChunkName: "bar" */ new URL("../bar.ts", import.meta.url)); new Worker(new URL('./path', import.meta.url), /* @vite-ignore */ dynamicOptions);
Since esbuild can be used as a preprocessor for these tools (e.g. to strip TypeScript types), it can be problematic if esbuild doesn't do additional work to try to retain these comments. Previously esbuild special-cased Webpack comments in these specific locations in the AST. But Vite would now like to use similar comments, and likely other tools as well.
So with this release, esbuild now will attempt to preserve some comments inside of expressions in more situations than before. This behavior is mainly intended to preserve these special "magic comments" that are meant for other tools to consume, although esbuild will no longer only preserve Webpack-specific comments so it should now be tool-agnostic. There is no guarantee that all such comments will be preserved (especially when
--minify-syntax
is enabled). So this change does not mean that esbuild is now usable as a code formatter. In particular comment preservation is more likely to happen with leading comments than with trailing comments. You should put comments that you want to be preserved before the relevant expression instead of after it. Also note that this change does not retain any more statement-level comments than before (i.e. comments not embedded inside of expressions). Comment preservation is not enabled when--minify-whitespace
is enabled (which is automatically enabled when you use--minify
).
-
Publish a new bundle visualization tool
While esbuild provides bundle metadata via the
--metafile
flag, previously esbuild left analysis of it completely up to third-party tools (well, outside of the rudimentary--analyze
flag). However, the esbuild website now has a built-in bundle visualization tool:You can pass
--metafile
to esbuild to output bundle metadata, then upload that JSON file to this tool to visualize your bundle. This is helpful for answering questions such as:- Which packages are included in my bundle?
- How did a specific file get included?
- How small did a specific file compress to?
- Was a specific file tree-shaken or not?
I'm publishing this tool because I think esbuild should provide some answer to "how do I visualize my bundle" without requiring people to reach for third-party tools. At the moment the tool offers two types of visualizations: a radial "sunburst chart" and a linear "flame chart". They serve slightly different but overlapping use cases (e.g. the sunburst chart is more keyboard-accessible while the flame chart is easier with the mouse). This tool may continue to evolve over time.
-
Fix
--metafile
and--mangle-cache
with--watch
(#1357)The CLI calls the Go API and then also writes out the metafile and/or mangle cache JSON files if those features are enabled. This extra step is necessary because these files are returned by the Go API as in-memory strings. However, this extra step accidentally didn't happen for all builds after the initial build when watch mode was enabled. This behavior used to work but it was broken in version 0.14.18 by the introduction of the mangle cache feature. This release fixes the combination of these features, so the metafile and mangle cache features should now work with watch mode. This behavior was only broken for the CLI, not for the JS or Go APIs.
-
Add an
original
field to the metafileThe metadata file JSON now has an additional field: each import in an input file now contains the pre-resolved path in the
original
field in addition to the post-resolved path in thepath
field. This means it's now possible to run certain additional analysis over your bundle. For example, you should be able to use this to detect when the same package subpath is represented multiple times in the bundle, either because multiple versions of a package were bundled or because a package is experiencing the dual-package hazard.
All esbuild versions published in the year 2022 (versions 0.14.11 through 0.16.12) can be found in CHANGELOG-2022.md.
All esbuild versions published in the year 2021 (versions 0.8.29 through 0.14.10) can be found in CHANGELOG-2021.md.
All esbuild versions published in the year 2020 (versions 0.3.0 through 0.8.28) can be found in CHANGELOG-2020.md.