Enable esm named exports

[perrin4869]

Adds support for esm named exports

Fixes issue #2361

I tried to keep this as backwards compatible as possible, but some minor (undocumented) changes were made which may break people importing from the pkg directory directly.
Specifically we can't do require('sinon/pkg/sinon.js') or require('sinon/pkg/sinon-no-sourcemaps.js') anymore, as these were changed into cjs files.
An additional pkg/sinon.js file is produced, identical to pkg/sinon.cjs, to keep the WebWorker functional. importScripts seems to fail on cjs files.

How to verify

1. Check out this branch
2. npm ci
3. npm test
4. import { stub } from "sinon" from an esm javascript file on node >= 12 should work

Edit: this is more of a band-aid, since the preferred solution would be an esm rewrite and using rollup to produce a cjs and esm build.

[codecov]

Codecov Report

Merging #2382 (59aaaf6) into master (62b29c0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2382   +/-   ##
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  Coverage   96.07%   96.07%           
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  Files          41       41           
  Lines        1883     1883           
=======================================
  Hits         1809     1809           
  Misses         74       74           

Flag	Coverage Δ
unit	96.07% <ø> (ø)

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[fatso83]

Hi, Perrin. Thanks for this. As you probably saw in #2361 (comment), I had a go at this and found that, as you say, the best solution would just be to rewrite into ESM. I did have a go, but I found that the stuff I did always broke some kind of use case in some environment, so curious how this checks out.

Thanks!

[perrin4869]

Honestly I was thinking that even if it's a band-aid, this PR would still require a major version bump just to be on the safe side.
That said, we could still tweak around the exports field to try to make it as backwards compatible as possible.
Dropping support for node 10 would make things slightly simpler I think, it's a good chance as it has reached EOL.
I tested this on node 12 through 16 loading as commonjs and esm, and got positive results, the rest of the use-cases I wouldn't really know... but I did make sure tests are passing...

[fatso83]

I was just thinking of these use cases:

1. bundlers should not start having problems
2. node in ESM mode (i.e. loading usign import in *.mjs scripts) should work
3. node in require mode should work

Does the second point work with this? Or which envs work and how (i.e. which files need to be imported)?

[perrin4869]

1 I haven't tested neither webpack not rollup, but in theory they should work
2 and 3 I tested the following way:

❯ cat package.json
{
  "type": "module",
  "dependencies": {
    "sinon": "github:perrin4869/sinon#esm-named-exports"
  }
}
❯ cat index.js
import sinon from "sinon"
import { stub } from "sinon"

console.log(sinon)
console.log(stub)
❯ cat index.cjs
const { stub } = require('sinon');
console.log(stub);

Node >= 12 behaved as you'd expect

[mroderick]

Related to the discussion in this PR, I added some detail on converting the whole codebase to ESM: #2361 (comment)

[perrin4869]

Well, while I can totally get being hesitant about merging this in, this does get the job done for me now, and I am not sure how realistic this esm rewrite really is...
Maybe we could release this as a beta for people to test?

[fatso83]

I think this just stalled on me (and or others) just forgetting about it pre-holiday. Not intentional from my side, in any way. I do not mind merging this (AFAI can remember).

[perrin4869]

I'd love to see this merge as this is one of the biggest pain points for me moving to esm modules :)

[fatso83]

Released as Sinon 12! Thanks @perrin4869 <3

[fatso83]

@perrin4869 Seems this broke webpack bundling for CJS. See #2411. Any quickfix?

[perrin4869]

ah dammit ><;; Let me look into this!