fix(turbopack): ignore missing optional peerDependencies

[scs0209]

Bug

Fixes #97870

Turbopack fails to resolve packages that require() a missing optional peer dependency, while webpack succeeds via OptionalPeerDependencyResolverPlugin.

Reproduction: https://github.com/scs0209/nextjs-optional-peer-turbopack-repro

• next build (Turbopack) → Module not found: Can't resolve 'foo'
• next build --webpack → succeeds

Fix

In Turbopack module resolution, when a bare package request cannot be found, check the nearest package.json for peerDependenciesMeta[name].optional === true and resolve to Ignore (same outcome as webpack’s path: false).

Also restores the long-skipped e2e case in test/e2e/transpile-packages by moving the route out of the private _peer-deps folder (App Router ignores _ segments) to peer-deps.

Test plan

• cargo test -p turbopack-tests --test execution optional_peer_dependency
• Unskipped test/e2e/transpile-packages optional peer case (route rename)
• CI e2e for test/e2e/transpile-packages

Made with Cursor