Merge user resolve.conditions in @tailwindcss/vite CSS @import resolver

[Dextheking1]

Fixes #20426.

Summary

@tailwindcss/vite resolves CSS @import with a custom Vite resolver. That resolver spread the user's resolve config but then overwrote conditions with a hardcoded list (['style', 'development|production']), so user-configured resolve.conditions were silently dropped for CSS @import even though they were honoured for JS imports. This happened in both resolver branches (legacy pre-Environment-API and Environment API).

The fix merges instead of overwrites:

conditions: ['style', 'development|production', ...(config!.resolve.conditions ?? [])]

so the built-in conditions keep priority while user conditions still apply.

Test plan

• Added regression tests in integrations/vite/resolvers.test.ts covering both resolver branches: vite ^8 (Environment API) and vite ^5.3.5 (legacy). A fixture package exposes ./custom.css under a my-custom-condition export and ./default.css under style/default; with resolve.conditions: ['my-custom-condition'] the built CSS must contain the custom-condition rule. 2/2 new tests pass; full vite/resolvers.test.ts: 15/15 pass.
• Verified with the real Vite 8 resolver using the exact option shapes: old shape resolved default.css (bug reproduced), new shape resolves custom.css (fixed).
• Prettier clean on both changed files; tsc reports 0 errors in the changed file (remaining 39 errors elsewhere in the monorepo are pre-existing environmental issues unrelated to this change).

Note: the fixture includes @import 'tailwindcss'; in the test CSS (with an explanatory comment) because the plugin returns early for files without Tailwind features, so the resolver under test would never run otherwise.

[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: ff18815c-3019-4e25-ad4a-0bcfdfde04ad

📥 Commits

Reviewing files that changed from the base of the PR and between 41d9cae and 5a7e9bc.

📒 Files selected for processing (2)

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

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

---

Walkthrough

The Vite plugin now appends user-provided resolve.conditions to the built-in CSS resolver conditions in both the legacy and Environment API paths. A parameterized integration test covers Vite ^8 and ^5.3.5 and verifies that a custom conditional CSS export is selected.

Priority: ➖ Normal

Severity of issue fixed: Medium

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the bug, the fix, the affected resolver branches, and the regression tests. It directly matches the changeset and objectives.
Title check	✅ Passed	The title clearly and concisely describes the main change: merging user-provided Vite resolve conditions in the CSS import resolver.
Linked Issues check	✅ Passed	The pull request satisfies issue #20426. In packages/@tailwindcss-vite/src/index.ts, the legacy resolver appends config.resolve.conditions after style and development|production. The Environme…
Out of Scope Changes check	✅ Passed	The changes stay within issue #20426. The source changes modify only CSS resolver condition merging in the two supported resolver branches. The added test changes verify this behavior. No unrelated pr…

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the implementation is narrowly scoped and both supported resolver paths have meaningful regression coverage.

_{Reviews (1) · Last reviewed commit: "fix(vite): merge user resolve.conditions..."}