Summary

I would like to have a monorepo package that declares a peerDependency, but doesn't install it. Installing it has the effect of causing it to reference that version of the dependency when run within the monorepo. That is incorrect behavior, I want it to never install and always depend on the depending package's installation. (When useWorkspaces is set to true, this works correctly).

When autoInstallPeers is false (via pnpm-config.json or .npmrc, and useWorkspaces is set to false, Rush will incorrectly install all peerDependencies of packages in the monorepo.

Repro steps

See repro repo here

But:

1. Use pnpm as the package manager
2. Have useWorkspaces disabled
3. Have autoInstallPeers:false
4. Have a monorepo package that has a peerDependency declared

Expected result:
The peerDependency is not listed in the package's node_modules folder
Actual result:
The peerDependency IS listed in he package's node_modules folder

Details

This problem is caused by RushInstallManager's usage of PackageJsonEditor.dependencyList. It adds peerDependencies to the same list as regular dependencies. This makes sense if autoInstallPeers is false, but not when it's true.

I'm going to open a PR with a suggested fix, but I think there should be a case specifically for PNPM & autoInstallPeers:false, that checks for peerDeps and excludes them from being added to the tempDependencies Map.

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