fix(vite): resolve tsconfig paths in CSS and JS resolvers

[nightah]

Change aliasOnly from true to false when calling Vite's resolver so that the full resolution pipeline runs, including the oxc resolver responsible for tsconfig path resolution.

When aliasOnly was true, only the @rollup/plugin-alias plugin ran, which meant resolve.tsconfigPaths: true had no effect on CSS @import or JS @plugin resolution in @tailwindcss/vite.

Closes #19802.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Review profile: CHILL

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Run ID: d1c0bc1e-509b-44cb-be18-bcf7ee45b47e

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Reviewing files that changed from the base of the PR and between 12c1e7e and 941631b.

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• packages/@tailwindcss-vite/src/index.ts

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Walkthrough

The pull request adds an import for json in the Vite resolvers test and two new tests that verify tsconfig path resolution in both production build and dev server modes, asserting emitted CSS contains expected utilities. Separately, the Vite integration resolver logic is changed so CSS and JS resolvers are invoked with false for the CSS-related flag and CSS-only results are enforced by returning undefined when a resolved path does not end with .css; these changes apply to both environment-less and environment-present code paths.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly describes the main change: fixing Vite resolver to support tsconfig path resolution for CSS and JS resolvers.
Description check	✅ Passed	The description accurately explains the root cause and solution: changing aliasOnly from true to false to enable the full Vite resolution pipeline including oxc resolver.
Linked Issues check	✅ Passed	The PR changes address the core requirement from #19802: modifying aliasOnly from true to false in both environment-less and environment-present branches to enable tsconfig path resolution.
Out of Scope Changes check	✅ Passed	All changes are directly related to the objective: modifying CSS/JS resolver calls and adding test cases for tsconfig path resolution in Vite builds.

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[coderabbitai]

🧹 Nitpick comments (1)

integrations/vite/resolvers.test.ts (1)

15-165: Optional: extract shared fixture setup to reduce duplication.

Both new tests repeat the same filesystem fixture; extracting a small helper/object for shared files would make future resolver test updates less error-prone.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@integrations/vite/resolvers.test.ts` around lines 15 - 165, Extract the
duplicated filesystem fixture used in the two tests titled "resolves tsconfig
paths in production build" and "resolves tsconfig paths in dev mode" into a
shared constant (e.g., sharedFs) and reference that constant in each test's
options instead of duplicating the object; update the tests to pass the sharedFs
to the test helper (replace the inline fs: { ... } blocks with fs: sharedFs) so
future changes to the fixture live in one place and both tests (production build
and dev mode) reuse the same setup.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@integrations/vite/resolvers.test.ts`:
- Around line 15-165: Extract the duplicated filesystem fixture used in the two
tests titled "resolves tsconfig paths in production build" and "resolves
tsconfig paths in dev mode" into a shared constant (e.g., sharedFs) and
reference that constant in each test's options instead of duplicating the
object; update the tests to pass the sharedFs to the test helper (replace the
inline fs: { ... } blocks with fs: sharedFs) so future changes to the fixture
live in one place and both tests (production build and dev mode) reuse the same
setup.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: a1c6b6ce-a66b-41d5-a9dd-78be04245a20

📥 Commits

Reviewing files that changed from the base of the PR and between a4be983 and 12c1e7e.

📒 Files selected for processing (2)

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

[RobinMalfait]

Hey! Looks like CI is failing. Do you mind making sure that things work as expected? Thanks!

[nightah]

Thanks for the ping @RobinMalfait. I believe this is now fixed.

When aliasOnly was changed to false, the full Vite resolution pipeline could resolve bare specifiers like tailwindcss to JS entry points (e.g. lib.mjs) instead of CSS files. The enhanced-resolve fallback, which respects mainFields: ['style'], never ran.

That said, I'm unsure whether the remaining test failures are related to my change or an environmental issue.
Following the contribution guidelines after getting to pnpm build and pnpm test:integrations against a4be983 for a baseline, the following tests failed for me:

• oxide/wasm.test.ts: wasm32-wasi loading (timeout)
• postcss/source.test.ts: (these look like they didn't even fail in CI)
• vite/nuxt.test.ts: build (timeout)
• vite/qwik.test.ts: dev mode (pnpm install warning causing failure)