FIX for webpack: Export binary files in javascript package

[dlech]

Description

This adds the distributed binary files to the "exports" section of the package.json file. This allows the files to be referenced, e.g. by require.resolve('pyodide/distutils.tar') which is useful for tools like webpack.

Checklists

• Add a CHANGELOG entry

[dlech]

Another user who would benefit from this change: https://github.com/mneil/pyodide-webpack/blob/main/patch.js

[hoodmane]

Well we can do this but we probably won't call it a breaking change if we rename, move, or delete these files since they are supposed to be internal.

[hoodmane]

But I suppose that the webpack use case only relies on the fact that we export all files that we need internally so if we move them it won't break webpack users.

[hoodmane]

Oh I see they are here:
https://github.com/mneil/pyodide-webpack/blob/main/webpack.config.js#L39-L44
We should probably have our own webpack plugin that does this so that downstream doesn't need to know the exact list of files we use.

[dlech]

We should probably have our own webpack plugin

That would be great - unless you use something like Create React App that doesn't allow access to the webpack config.

[hoodmane]

unless you use something like Create React App that doesn't allow access to the webpack config.

I don't think Pyodide is ever likely to work with create react app, though of course if someone figures out a way maybe we can think about supporting it. The best we can do for now is to document that we don't know how to use them together.

[hoodmane]

webpack plugin

I would appreciate it if someone else could help with this though. I've tried to write a webpack plugin several times but always run into the problem that I was unable to use webpack with Pyodide at all. Perhaps with @mneil's example I would have an easier time, but the webpack plugin API is also very confusing. If it's just a wrapper around CopyPlugin then that probably isn't too hard.

In @mneil's example, he also patches pyodide.js to remove the global assignment to loadPyodide, but if you use pyodide.mjs instead of pyodide.js it doesn't assign loadPyodide to the global scope. We make pyodide.js out of pyodide.umd.ts which just adds the globalThis assignment to pyodide.ts:
https://github.com/pyodide/pyodide/blob/main/src/js/pyodide.umd.ts
Whereas pyodide.mjs is made from pyodide.ts directly. Though deleting that line is also an option if using webpack to load a module is not possible.

[hoodmane]

Thanks for all your help with this @dlech!

[hoodmane]

Okay after some discussion @mneil and @dlech have convinced me that this is a good idea. Thanks guys!

[hoodmane]

Since this PR was opened, we apparently changed the name of distutils.tar to distutils-1.0.0.zip.