Enable detectAsyncLeaks in Vitest tests

[Copilot]

Enables detectAsyncLeaks: true in all node-environment Vitest configurations to detect asynchronous resource leaks (e.g., uncleared timers, pending promises) in node-based test runs. Also upgrades vitest to 4.1.5 (stable release), which includes TypeScript type support for the detectAsyncLeaks option.

Changelog

New

• detectAsyncLeaks: true added to all node-environment vitest configs:
  • packages/react/vitest.config.mts
  • packages/doc-gen/vitest.config.mts
  • packages/styled-react/vitest.config.ts
  • packages/postcss-preset-primer/vitest.config.ts

Changed

• Upgraded vitest, @vitest/browser, and @vitest/browser-playwright from ^4.0.15 to ^4.1.5 to support the detectAsyncLeaks TypeScript type in InlineConfig

Removed

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Config-only change with a vitest dev-dependency bump. No public API impact.

Testing & Reviewing

Browser-based vitest configs (vitest.config.browser.mts, vitest.config.browser.ts) are intentionally excluded — detectAsyncLeaks uses Node.js async_hooks and is not applicable to Chromium/Playwright environments.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github-ui (Learn more about how to run integration tests)

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Latest commit: 572f65c

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[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Or, apply the integration-tests: skipped manually label to skip these checks.

[siddharthkp]

@copilot Can you see the CI / type-check error and fix it?

[Copilot]

@copilot Can you see the CI / type-check error and fix it?

Fixed in b9ab414. The detectAsyncLeaks option was added in vitest 4.1.0-beta.4, but the project was on 4.0.15. The type-check in postcss-preset-primer failed because detectAsyncLeaks didn't exist in InlineConfig. I upgraded vitest, @vitest/browser, and @vitest/browser-playwright from ^4.0.15 to ^4.1.0-beta.6.

[github-actions]

Hi! This pull request has been marked as stale because it has been open with no activity for 60 days. You can comment on the pull request or remove the stale label to keep it open. If you do nothing, this pull request will be closed in 7 days.

[siddharthkp]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved in 572f65c. The conflicts were in package.json and package-lock.json — I merged with origin/main and resolved by taking the newer stable versions (vitest ^4.1.5, typescript-eslint ^8.57.0, etc.) from main. The detectAsyncLeaks: true additions in all node-environment vitest configs are preserved.