Yarn PnP support

[nicolo-ribaudo]

I'm trying to upgrade Babel to use Yarn PnP, but it has a problem with debug because it require()s supports-color without declaring it in package.json.

Would it be possible to declare it as a peerDependency?

Note that this issue isn't urgent (I currently have a workaround), but PnP will be enabled by default in yarn 2.

cc @arcanis

[arcanis]

Note that in the context of debug the best option is probably an optional peer dependency, since the require is in a try/catch. This way you won't get warnings even if support-colors is missing 🙂

[Qix-]

#709 #612

[nicolo-ribaudo]

Sorry, I searched for "pnp" in issues and didn't find anything, and I forgot to search in PRs 😅

[MonstraG]

Hi. It's been about 3 years.

Both things linked here:

#709 #612

Are closed without proper resolution, in lieu of #556, which is sitting open for the last 4 years.

Can we pretty please fix this?

[arcanis]

I believe it's been fixed a while ago, supports-color is listed as an optional peer dependency. #556 has no connection I can see to this former issue.

[MonstraG]

Sadly, this is still happening to me:

vulcan.userweb:dev: warn - ../../.yarn/__virtual__/debug-virtual-252d10c791/0/cache/debug-npm-4.3.4-4513954577-3dbad3f94e.zip/node_modules/debug/src/node.js
vulcan.userweb:dev: Module not found: debug tried to access supports-color (a peer dependency) but it isn't provided by its ancestors; this makes the require call ambiguous and unsound.
vulcan.userweb:dev:
vulcan.userweb:dev: Required package: supports-color
vulcan.userweb:dev: Required by: debug@virtual:4.3.4 (via repo_folder/.yarn/__virtual__/debug-virtual-252d10c791/0/cache/debug-npm-4.3.4-4513954577-3dbad3f94e.zip/node_modules/debug/src/)
vulcan.userweb:dev:
vulcan.userweb:dev: Ancestor breaking the chain: @babel/core@npm:7.21.0
vulcan.userweb:dev: Ancestor breaking the chain: @babel/traverse@npm:7.21.2
vulcan.userweb:dev: Ancestor breaking the chain: @eslint/eslintrc@npm:0.4.3
vulcan.userweb:dev: Ancestor breaking the chain: @eslint/eslintrc@npm:2.0.0
vulcan.userweb:dev: Ancestor breaking the chain: @humanwhocodes/config-array@npm:0.11.8
vulcan.userweb:dev: Ancestor breaking the chain: @humanwhocodes/config-array@npm:0.5.0
vulcan.userweb:dev: Ancestor breaking the chain: @typescript-eslint/parser@virtual:5.54.1
vulcan.userweb:dev: Ancestor breaking the chain: @typescript-eslint/parser@virtual:5.54.1
vulcan.userweb:dev: Ancestor breaking the chain: @typescript-eslint/typescript-estree@virtual:5.54.1
vulcan.userweb:dev: Ancestor breaking the chain: @typescript-eslint/typescript-estree@virtual:5.54.1
vulcan.userweb:dev: Ancestor breaking the chain: agent-base@npm:6.0.2
vulcan.userweb:dev: Ancestor breaking the chain: agentkeepalive@npm:4.3.0
vulcan.userweb:dev: Ancestor breaking the chain: eslint@npm:7.32.0
vulcan.userweb:dev: Ancestor breaking the chain: eslint@npm:8.35.0
vulcan.userweb:dev: Ancestor breaking the chain: eslint-import-resolver-typescript@virtual:2.7.1
vulcan.userweb:dev: Ancestor breaking the chain: eslint-import-resolver-typescript@virtual:3.5.3
vulcan.userweb:dev: Ancestor breaking the chain: http-proxy-agent@npm:5.0.0
vulcan.userweb:dev: Ancestor breaking the chain: https-proxy-agent@npm:5.0.1
vulcan.userweb:dev: Ancestor breaking the chain: ioredis@npm:5.3.1
vulcan.userweb:dev: Ancestor breaking the chain: istanbul-lib-source-maps@npm:4.0.1
vulcan.userweb:dev: Ancestor breaking the chain: socks-proxy-agent@npm:7.0.0

Although it seems that my case is a bit more complicated, but I am really out of options on what to do here.

Using a monorepo, shared package accesses ioredis, which pulls down all of this. Adding packageExtensions doesn't help. Adding debug or supports-color everywhere I can, both in dependencies and resolutions doesn't help either.

Actually, scratch that, it seems that adding "supports-color": "<9.0.0", in devDependencies of root package.json and nowhere else seems to work. I have no idea why.

[arcanis]

As indicated in the error message, debug lists supports-color correctly, it just can't be found because the debug consumers don't actually fulfil the peer dependency:

debug tried to access supports-color (a peer dependency) but it isn't provided by its ancestors

It's usually not a problem because debug makes the require call within a try/catch statement, so errors are silently ignored. If you get a warning, I'd imagine it's caused by whatever your bundler is, which perhaps isn't smart enough to understand that resolution errors within try/catch statements shouldn't be surfaced.

Actually, scratch that, it seems that adding "supports-color": "<9.0.0", in devDependencies of root package.json and nowhere else seems to work. I have no idea why.

It works because of the fallback. Explicitly listing debug in the top-level manifest allows debug to access supports-color even if its consumers don't provide it themselves. Your bundler's resolution succeeds, so no warnings are emitted.