perf(ActionList): enable React Compiler

[hectahertz]

Closes #

Enable React Compiler for ActionList, the foundational component used by ActionMenu, SelectPanel, NavList, and FilteredActionList.

ActionList was originally excluded from the compiler during the initial migration. After analysis (build, lint with eslint-plugin-react-compiler, and manual Storybook verification), all ActionList source files are fully compiler-compatible. The only fix needed was a Rules of Hooks violation in a story file (ChildWithSideEffects, moved SideEffectDescription to module scope).

With the compiler enabled, React will automatically memoize ActionList's components (Item, List, Group, Selection, Visuals, etc.), reducing unnecessary re-renders without manual React.memo / useMemo / useCallback.

Changelog

New

N/A

Changed

• Removed src/ActionList/**/*.tsx from the React Compiler unsupported list in react-compiler.mjs
• Fixed nested component definition in ChildWithSideEffects story

Removed

N/A

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

Testing & Reviewing

1. Ran npx eslint with react-compiler/react-compiler rule on all ActionList files (source, stories, tests): 0 warnings
2. npx turbo build --filter=@primer/react --force passes with ActionList compiled
3. Verified in Storybook: ActionList Default, Single Select, Multi Select, With Avatars, ActionMenu with 100 items, SelectPanel default, NavList default

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

[changeset-bot]

🦋 Changeset detected

Latest commit: 7bb57e1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

👋 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.

[Copilot]

Pull request overview

This PR enables React Compiler for ActionList components — a foundational component used by ActionMenu, SelectPanel, NavList, and FilteredActionList. The compiler will automatically optimize re-renders without manual memoization, improving performance for one of the most-rendered list components in the design system.

Changes:

• Removed ActionList from the React Compiler unsupported list
• Fixed a Rules of Hooks violation by moving a nested component to module scope in a story file

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/react/src/ActionList/ActionList.features.stories.tsx	Moved SideEffectDescription component from nested definition to module scope to comply with Rules of Hooks
packages/react/script/react-compiler.mjs	Removed src/ActionList/**/*.tsx from the unsupported components list
.changeset/actionlist-react-compiler.md	Added changeset documenting the performance improvement

[francinelucca]

✨

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/13846

[primer-integration]

Integration test results from github/github-ui:

  CI Passed
  VRT Passed
  Projects Passed

All checks passed!