Fix scanning Yarn PnP workspace packages

[OllieinCanada]

Summary

• Resolve Yarn PnP virtual source bases to their real backing directories only at the Vite-to-native-scanner boundary.
• Preserve the original CSS/JS module identity and every source pattern and negation for compiler and resolver behavior.
• Leave ZIP-backed paths untouched because resolveVirtual can still return a path inside a ZIP archive; this is not a general PnP filesystem implementation.
• Add a packed-artifact Yarn PnP integration test whose React peer dependency demonstrably creates a virtual workspace path. The test covers source(none), an explicit source, a negated source, prefixing, and a relative JS plugin.

Fixes #17739.

Test plan

pnpm --filter @tailwindcss/vite build
pnpm exec prettier --check packages/@tailwindcss-vite/src/index.ts integrations/vite/yarn-pnp.test.ts
pnpm exec vitest run --root=./integrations vite/yarn-pnp.test.ts

The packed-artifact regression was checked against an unmodified current-main Vite tarball: baseline fails to emit the workspace utilities, the candidate passes, swapping back to baseline fails again, and restoring the candidate passes. A normal non-PnP Vite smoke build produced byte-identical CSS, and an alternating 20-build benchmark showed no meaningful overhead.

Scope

This fixes scanning for Yarn virtual packages backed by real files. It intentionally does not make Oxide scan Yarn ZIP archives or Vite in-memory virtual modules.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with no concrete correctness, security, or repository-rule violations identified.

_{Reviews (1) · Last reviewed commit: "Fix scanning Yarn PnP workspace packages"}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: 559400ab-6a78-486a-a603-da69a0a30eb2

📥 Commits

Reviewing files that changed from the base of the PR and between 41d9cae and 249ff13.

📒 Files selected for processing (2)

• integrations/vite/yarn-pnp.test.ts
• packages/@tailwindcss-vite/src/index.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review.

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Walkthrough

The Vite plugin now resolves Yarn PnP virtual source paths before constructing its scanner. It preserves paths that resolve inside zip archives. A new integration test creates a Yarn 4 workspace, verifies virtual dependency resolution, runs a Vite build, and checks that expected utilities are generated while excluded utilities are absent.

Priority: ➖ Normal

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 249ff

The Yarn PnP scanner-path change is covered by an integration test and does not leave a concrete merge-blocking risk.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description directly explains the Yarn PnP scanning fix, its scope, integration test coverage, validation steps, and known ZIP-backed limitations.
Title check	✅ Passed	The title clearly and concisely identifies the main change: fixing scanning of Yarn PnP workspace packages.
Linked Issues check	✅ Passed	The PR addresses issue #17739. packages/@tailwindcss-vite/src/index.ts resolves Yarn PnP virtual source bases with Module.findPnpApi(...).resolveVirtual(...) before native scanner construction. It…
Out of Scope Changes check	✅ Passed	The changed files stay within issue #17739. The implementation changes Vite scanner path handling for Yarn PnP packages. The integration test validates the reported monorepo failure mode and related s…

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