fix: linked strategy fixes for scoped packages, aliases, and peer deps

[manzoorwanijk]

We're looking at using install-strategy=linked in the Gutenberg monorepo (~200 workspace packages), which powers the WordPress Block Editor. While testing it in a PR, we ran into several issues with the linked strategy that this PR fixes.

Summary

1. Scoped workspace packages were losing their @scope/ prefix in node_modules because the symlink name came from the folder basename instead of the package name.
2. Aliased packages (e.g. "prettier": "npm:custom-prettier@3.0.3") in workspace projects were getting symlinked under the real package name instead of the alias, so require('prettier') would fail.
3. With legacy-peer-deps = true, peer dependencies weren't being placed alongside packages in the store, so require() calls for peer deps failed from within the store.
4. With strict-peer-deps = true, the linked strategy could crash with Cannot read properties of undefined when store entries or parent nodes were missing for excluded peer deps.

Root cause

assignCommonProperties was using a single result.name for both consumer-facing symlinks and store-internal paths. For workspaces, node.name comes from the folder basename (missing the scope). For aliases, node.packageName gives the real name but we need the alias for the consumer symlink.

Separately, legacy-peer-deps tells the arborist to skip creating peer dep edges entirely, so the isolated reifier never saw them and never placed them in the store. And strict-peer-deps can cause nodes to be excluded from the tree while still being referenced by edges, leading to undefined lookups.

Changes

• Split proxy identity into result.name (consumer-facing: alias or scoped workspace name) and result.packageName (store-internal: real package name from package.json). Store paths (getKey, treeHash, generateChild, processEdges, processDeps) use packageName; consumer symlinks keep using name.
• When legacyPeerDeps is enabled, resolve missing peer dep edges from the tree via node.resolve() so they still get symlinked in the store.
• Guard against undefined from and target nodes in processEdges/processDeps to prevent crashes with strict-peer-deps.
• Guard idealTree.children.get(ws) in reify.js since the isolated tree uses an array for children, not a Map.
• Test fixture updates: recursive: true for mkdirSync, scoped workspace glob support.
• New tests for scoped workspace packages, aliased packages in workspaces, and peer deps with legacyPeerDeps.

References

Fixes #6122

[owlstronaut]

@manzoorwanijk could you get the CI passing before I do a deep-dive on this?

[manzoorwanijk]

@owlstronaut Thank you for looking into it. I have updated the test coverage that should make CI happy.

[owlstronaut]

Thank you @manzoorwanijk , this looks great! I created some experiments here to run and they all seem good as well. Appreciate your work on this!

[manzoorwanijk]

@owlstronaut Thank you for shipping this.

I was wondering whether it’s possible to backport the changes to v10.
I would be more than happy to spin up a PR.

[manzoorwanijk]

I have created #9011 to backport the changes to v10. Is there anything else that needs to be done for the backport?