fix #2388: allow consuming types without dom types

[remcohaszing]

Currently the TypeScript types for esbuild depend on the DOM types. However, esbuild itself does not depend on the DOM.

This change uses type augmentation to make the type error go away, while keeping backwards support for use with the DOM types.

Closes #2388

[evanw]

Ok, I can give this a try, but I reserve the right to revert this if it causes other problems. It looks like avoiding dom types also requires URL to be defined, so I'll add that too.

Seems kind of weird for using esbuild to be polluting the global type scope, but I guess that's just how TypeScript works. It's too bad TypeScript doesn't have some sort of if typeof WebAssembly !== 'undefined' for types.

[remcohaszing]

I reserve the right to revert this if it causes other problems

Of course you do! You are the maintainer ❤️

It looks like avoiding dom types also requires URL to be defined, so I'll add that too.

Nice catch! This is less apparent, as people often use the dom types or @types/node, both if which specify URL.

Seems kind of weird for using esbuild to be polluting the global type scope, but I guess that's just how TypeScript works. It's too bad TypeScript doesn't have some sort of if typeof WebAssembly !== 'undefined' for types.

You can, but it’s quite hacky. (playground link)

type Fallback = never

// @ts-ignore
type InternalURL = any extends URL ? Fallback : URL

This only works from handwritten type definition files, not from TypeScript source files.