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Subpath imports in ESM mode #688
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FWIW, I got my own application to work after I did modifications summarized by this gist. The rabbithole went pretty deep. I hope this will be useful for anyone stumbling upon this until ESM mode starts working properly for Notice that my usecase might be different from yours and there might be additional setup for those |
Here are the scripts that I use to produce the file layout described in suggested solution part (entrypoint is {
"scripts": {
"build:ci": "yarn run clear-build-artifacts && yarn run compile-d-ts-files && yarn run tsc --outDir ./dist-esm && yarn run tsc --module CommonJS --outDir ./dist-cjs && yarn run format-output-files && yarn run fix-subpath-exports",
"clear-build-artifacts": "rm -rf dist dist-ts dist-cjs dist-esm build",
"compile-d-ts-files": "yarn run tsc --removeComments false --emitDeclarationOnly --declaration --declarationDir ./dist-ts && yarn run copy-d-ts-files && yarn run tsc:plain --project tsconfig.out.json",
"copy-d-ts-files": "find ./src -mindepth 1 -maxdepth 1 -name '*.d.ts' -exec cp {} ./dist-ts +",
"fix-subpath-exports": "mkdir <SUBPATH> && cp package.json.<SUBPATH> <SUBPATH>/package.json",
"format-output-files": "find dist-ts -name '*.ts' -type f -exec sh -c \"echo '/* eslint-disable */\n/* eslint-enable prettier/prettier */'\"' | cat - $1 > $1.tmp && mv $1.tmp $1' -- {} \\; && eslint --no-eslintrc --config '.eslintrc.output.ts.cjs' --fix './dist-ts/**/*.ts' && eslint --no-eslintrc --config '.eslintrc.output.cjs' --fix 'dist-cjs/*js' 'dist-esm/*js'",
"lint": "eslint ./src --ext .ts,.tsx",
"tsc": "tsc --project tsconfig.build.json",
"tsc:plain": "tsc",
}
} Notice that when dealing with large number of supported subpath exports, like all Here are the TSConfig files used by script: // tsconfig.out.json
{
// TS config file for formatting the resulting .d.ts files (<project name>/dist-ts/**/*.d.ts) that end up in NPM package for typing information.
"extends": "./tsconfig.json",
"compilerOptions": {
"rootDir": "./dist-ts",
"noEmit": true
},
"include": [
"./dist-ts/**/*"
]
} // tsconfig.build.json
{
// TS config file to use to compile <project name>/src/**/*.ts files in CI.
"extends": "./tsconfig.json",
"compilerOptions": {
// We don't want dangling // eslint-disable-xyz comments, as that will cause errors during formatting output .[m]js files.
"removeComments": true
},
} And then the normal P.S. No need to take this whole process into use. Just pick the parts which you think suits best to whatever approach you are using to build & publish packages. To be fair, I am happy with anything that makes subpath imports work in ESM mode. :) |
@gcanti I took a look at the package.json of this project, and I think I could contribute a PR related to this issue. Would you like me to do that, or are you handling this via some internal ideas/pipelines? |
I'm working on a new iteration of |
Oh, I see, really interesting to hear about the new iteration, as well as it being included to |
🐛 Bug report
Please notice that this problem actually spans a wide range of
-ts
packages. At least the following are affectedCurrent Behavior
If using the following subpath import:
And then running using
ts-node
with--esm
flag, or ESM-based bundler (e.g. Vite), while things look OK in IDE, at runtime, there will be error:This happens because there is no matching entry for
PathReporter
subpath inpackage.json
file ofio-ts
package.Note that everything works fine when in CJS mode.
Expected behavior
I expect subpath imports of
io-ts
behave successfully at both compile- as well as runtime, both with CJS modules and ESM modules.Without any additional setup.
Reproducible example
Create
package.json
withio-ts
dependency:Add basic TS configuration to
tsconfig.json
:Create file
src/index.ts
with the following code:and try to execute it:
Suggested solution(s)
It looks like a whole family of
-ts
packages should be migrated to ESM era. The current setup is extremely weird, lacking"type": "module"
entry from package.json files, and duplicating.d.ts
files, which also use/lib
or/es6
imports interchangeably (sometimes ES6 things including fromxyz-ts/lib/abc
). This results subpath imports for-ts
packages being completely unuseable in ESM.There are I guess many approaches to solve this. I think it is important to retain CJS functionality still, but also enable everything work for ESM without additional setup. I personally flavor this pattern, which I found to be working for all my packages (note that order of
"types"
,"import"
, and"require"
in the file is meaningful!). I keep.d.ts
files in their owndist-ts
folder, all the CJS-flavored.js
files in their owndist-cjs
folder, and finally all ESM-flavored.js
files in their owndist-esm
folder. I ended up with this setup after long experiments with subpath imports, both outside of module, and within.If I want to enable subpath export for e.g.
my-subpath
, I need to first modify theexports
inpackage.json
:And then create the following stub package file to
./my-subpath/package.json
path within distributed NPM package (this is only for CJS support):Technically, only
main
property is needed, but the others are just in case.This setup allows the same subpath imports always to work, no matter whether they are in TS, CJS, or ESM mode. Furthermore, it adhers to DRY principle, so that it doesn't duplicate
.d.ts
files.Additional context
Your environment
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