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claude-code

Claude-skill-registry feature-flags

Use when feature flag tests fail, flags need updating, understanding @gate pragmas, debugging channel-specific test failures, or adding new flags to React.

install
source · Clone the upstream repo
git clone https://github.com/majiayu000/claude-skill-registry
Claude Code · Install into ~/.claude/skills/
T=$(mktemp -d) && git clone --depth=1 https://github.com/majiayu000/claude-skill-registry "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/data/feature-flags-chltjs1921-udemy-github-tags-de" ~/.claude/skills/majiayu000-claude-skill-registry-feature-flags && rm -rf "$T"
manifest: skills/data/feature-flags-chltjs1921-udemy-github-tags-de/SKILL.md
source content

React Feature Flags

Flag Files

FilePurpose
packages/shared/ReactFeatureFlags.js
Default flags (canary), 
__EXPERIMENTAL__
overrides
packages/shared/forks/ReactFeatureFlags.www.js
www channel, 
__VARIANT__
overrides
packages/shared/forks/ReactFeatureFlags.native-fb.js
React Native, 
__VARIANT__
overrides
packages/shared/forks/ReactFeatureFlags.test-renderer.js
Test renderer

Gating Tests

@gate
pragma (test-level)

Use when the feature is completely unavailable without the flag:

// @gate enableViewTransition
it('supports view transitions', () => {
  // This test only runs when enableViewTransition is true
  // and is SKIPPED (not failed) when false
});


gate()
inline (assertion-level)

Use when the feature exists but behavior differs based on flag:

it('renders component', async () => {
  await act(() => root.render(<App />));

  if (gate(flags => flags.enableNewBehavior)) {
    expect(container.textContent).toBe('new output');
  } else {
    expect(container.textContent).toBe('legacy output');
  }
});

Adding a New Flag

  1. Add to 
    ReactFeatureFlags.js
    with default value
  2. Add to each fork file (
    *.www.js
    , 
    *.native-fb.js
    , etc.)
  3. If it should vary in www/RN, set to 
    __VARIANT__
    in the fork file
  4. Gate tests with 
    @gate flagName
    or inline 
    gate()

Checking Flag States

Use 

/flags
to view states across channels. See the 
flags
skill for full command options.

__VARIANT__
Flags (GKs)

Flags set to 

__VARIANT__
simulate gatekeepers - tested twice (true and false):

/test www <pattern>              # __VARIANT__ = true
/test www variant false <pattern> # __VARIANT__ = false

Debugging Channel-Specific Failures

  1. Run 
    /flags --diff <channel1> <channel2>
    to compare values
  2. Check 
    @gate
    conditions - test may be gated to specific channels
  3. Run 
    /test <channel> <pattern>
    to isolate the failure
  4. Verify flag exists in all fork files if newly added

Common Mistakes

  • Forgetting both variants - Always test 
    www
    AND 
    www variant false
    for 
    __VARIANT__
    flags
  • Using @gate for behavior differences - Use inline 
    gate()
    if both paths should run
  • Missing fork files - New flags must be added to ALL fork files, not just the main one
  • Wrong gate syntax - It's 
    gate(flags => flags.name)
    , not 
    gate('name')