What is the extent of Vite's CJS-ESM interoperability?

[silvenon]

Hello, I'm looking at #19036 and wondering if there's anything smaller that I should report, maybe to an upstream project like Rollup, regarding CommonJS interoperability.

For example I noticed that when using ssr.noExternal if a CJS package I installed does the following:

module.exports = {
  foo: require('./foo'),
}

The require() call will remain after vite build, which won't work in an ESM project, but if I move it out of the expression:

const foo = require('./foo')
module.exports = { foo }

the ./foo module will get inlined properly. Is this worth reporting to Rollup maybe?

Also, any usage of __dirname and __filename will remain as-is, they won't get converted to import.meta.dirname and import.meta.filename.

Is there some way to know the exact extent and the limitations of Vite's interoperability with CommonJS?

[sapphi-red]

For example I noticed that when using ssr.noExternal if a CJS package I installed does the following:

I guess it's because @rollup/plugin-commonjs does not support that case.
That case is difficult to determine whether it runs always:

module.exports = {
  foo: foo && require('./foo'), // this is conditional require
  bar: foo ? require('./foo') : false, // this is conditional require
}

const throw = () => { throw '' }
module.exports = {
  foo: (throw(), require('./foo')), // this is conditional require
}

any usage of __dirname and __filename will remain as-is, they won't get converted to import.meta.dirname and import.meta.filename.

Linking my comment here for reference: #19036 (comment)

Is there some way to know the exact extent and the limitations of Vite's interoperability with CommonJS?

I think there aren't any currently. For build, Vite uses @rollup/plugin-commonjs without any additional configuration so the README of it has the most information.