Adds support for PnP

[arcanis]

↪️ Pull Request

This PR adds support for PnP to the Parcel resolver.

Related: #2635

💻 Examples

Parcel running under Berry now works 💃

🚨 Test instructions

Unit tests usually are a bit impractical since it requires to run under a different environment (since it relies on process.versions.pnp). Any idea? I tested it locally by following the steps in the getting started (absolutely great experience btw!) and adding a require('lodash') in index.js.

To reproduce:

• Make a new project with Yarn and cd' into it
• Run yarn policies set-version berry
• Run yarn --version to confirm you're running with the v2
• Run yarn add lodash and add the require('lodash') to index.js
• Run yarn parcel index.html

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[DeMoorJasper]

Is there a way you could add a test for this?

Seems rather complex to test but would be nice if we have a test for it

_{Sent with GitHawk}

[arcanis]

Just pushed a commit with a test. I cheat a bit by modifying (then restoring) the environment but it should be fine as long as the tests don't run in parallel 🤞

I also had to commit the result of yarn install && yarn format, as they were changing other files than the ones affected by my PR.

[devongovett]

Awesome! Super excited about this.

[devongovett]

We may want to adjust this slightly so resolveModule is not called when using pnp, since that will still look for a node_modules directory (it calls findNodeModulePath). We'll need to split out the rest of that method so that things like aliases and builtins are still applied, but it doesn't search the filesystem.

[devongovett]

Alternatively, resolveModule could also check for pnp and skip looking for node_modules if it is available.

[arcanis]

Good idea, done 👍

[devongovett]

Does this also support pnp in yarn v1? Should it?

[arcanis]

@devongovett I haven't tested but it should, yes. The pnpapi package is exactly the same from the consumer perspective - only the internal implementation changes a bit.

Of course the v2 is so much better anyway 🤡

[arcanis]

Any blocker?

[arcanis]

Ping ? 😊

[mischnic]

@arcanis There is a lint error:

/Users/vsts/agent/2.150.3/work/1/s/packages/core/integration-tests/test/pnp.js
  2:7  error  'fs' is assigned a value but never used  no-unused-vars

[arcanis]

Ping @devongovett ? 🙂

[DeMoorJasper]

Looks good to me, although I don't think Parcel 1 should change this significantly and this should probably target Parcel 2

[texastoland]

I'm actively waiting on this to support some courses on egghead.io. Is there are part of the change that's too drastic?

[codyaverett]

This would be nice to have now. Are you all holding off on this for v2?

[DeMoorJasper]

Yes, this PR should be implemented for v2. Alpha's gonna come out soon and Parcel 1 should only receive bugfixes at this point.

It could be a seperate resolver plugin in Parcel 2

[DeMoorJasper]

closing in favor of #3582