[Yarn/Lerna] Workspaces: Watcher not working in v2

[krnlde]

🐛 bug report

🎛 Configuration (.babelrc, package.json, cli command)

• My whole configuration can be seen and cloned here https://github.com/lookmom/nohands/tree/feature/parcel2 (pinned version)
• You'll need node <=14 and yarn <= 1.22.10
• Install dependencies as usual with yarn install

🤔 Expected Behavior

when I start the project with yarn start and then change the HelloWorld component that is imported from a yarn workspace the project will not recompile. We've had numerous discussions about it. I reference them in the "context" part.

😯 Current Behavior

The Change is not recognized and the page stays pristine, when I change somethin inside the app workspace itself the watcher pics the changes up and recompiles. So that is not an issue.

💁 Possible Solution

Pick up changes from workspace imports like parcel v1 does.

🔦 Context

This same repo works in parcel v1. In fact you can reproduce the same steps in the main branch of the repo for comparison.

• Discussion about Lerna/ Yarn Workspaces: Some trouble with lerna-symlinked node_modules watching for v2 #5429
• Possible duplicate issue, though not sure if: Parcel 2 doesn't detect changes in linked dependencies. #4332
• Reply in an unrelated issue, re-assuring workspaces should be no problems: Invalid Version: undefined #5943 (comment)

💻 Code Sample

https://github.com/lookmom/nohands/tree/feature/parcel2 (pinned version)

🌍 Your Environment

Software	Version(s)
Parcel	parcel@2.0.0-beta.2
Node	node@v15.12.0
npm/Yarn	npm@7.6.3 , yarn@1.22.10
Operating System	Windows 10 Pro (Insider Preview 21337)

The issue is present in every parcel v2 version, in every node version starting from 12, in every yarn version starting from 1.22, in every Windows 10 version starting from 1907. Also tested in WSL with Ubuntu 20.10 with the same results.

[krnlde]

Alright! I have more insights on this bug.

TL;DR: If there is a false yarn.lock inside the starter workspace, the .parcel-cache will be created there and as a result the Watcher does not work properly.

In my case I start the app via parcel serve src/app/index.html and I had an old yarn.lock inside src/app. Parcel v2 then creates a src/app/.parcel-cache and the Watcher won't work properly. If I then remove the yarn.lock and start parcel again the .parcel-cache will be created in the root folder (as it should) and the Watcher works.

Still a bug or an improvement maybe.

[mischnic]

Starting from your entry points, Parcel finds the first directory that contains a lockfile or a.git folder. This is the project root (any files outside of that aren't watched)

Still a bug or an improvement maybe.

I'm not sure how this could be improved

[krnlde]

To clarify, I removed the dangling src/app/yarn.lock, nothing else, and it started working.

[krnlde]

Looks like this behaviour to me:

parcel/packages/core/package-manager/src/installPackage.js

Line 137 in eabbbec

'yarn.lock',

[mischnic]

No, it's here:

parcel/packages/core/core/src/resolveOptions.js

Line 48 in dea272f

let projectRootFile =

nothing else, and it started working.

Yes, I can see how this fixed your problem. But there's not much we can do apart from documenting this behaviour.

[krnlde]

Thank you. I'll close the issue since the actual problem is resolved.