[rush] (pnpm) Ignoring peer dependency

[anantoghosh]

Summary

For example when I install @emotion/react which has a optional peer dependency on @babel/core. We are not installing @babel/core as it not required for our build.

I tried to ignore it by setting in the projects's package.json

"pnpm": {
  "peerDependencyRules": {
    "ignoreMissing": [
      "@babel/core"
    ]
  }
}

as recommended by pnpm, but that does not seem to work within a rush repo. It works normally in a pnpm project just fine.

This prevents our projects from using strict peer dependencies, as it throws an error. Furthermore, it makes the rush update output quite verbose and full of warnings.

Repro steps

https://github.com/anantoghosh/rush-peer

Details

Current workaround is to install all the optional peers as well, but that may lead to unintended effects under certain cases.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/rush globally installed version?	5.62.2
rushVersion from rush.json?	5.63.0
useWorkspaces from rush.json?	true
Operating system?	Windows
Would you consider contributing a PR?	Yes
Node.js version (node -v)?	v16.13.2
pnpm	v6.32.3

[D4N14L]

We just run PNPM install when performing rush install, so I'm unsure why this wouldn't be working for you. Our own modifications on top of this are limited to .pnpmfile.cjs and generate a workspace file. Have you tried doing this with a vanilla PNPM workspace?

[anantoghosh]

@D4N14L thank you for your input, it helped me with further investigation. It turns out in a pnpm workspace, the pnpm key must be specified in the root package.json.
pnpm/pnpm#4306 (comment). Since rush does not expose the root package.json, is there any way we could specify it?

[elliot-nelson]

This configuration option is now officially supported in Rush 5.79+ in the pnpm-config file: https://github.com/microsoft/rushstack/blob/main/libraries/rush-lib/assets/rush-init/common/config/rush/pnpm-config.json

(if you run into any issues please file a new ticket.)