react-native/.github/actions/diff-js-api-changes/action.yml

name: diff-js-api-changes
description: Check for breaking changes in the public React Native JS API
outputs:
  message:
    description: Formatted markdown message describing API changes, or empty if no changes
    value: ${{ steps.format_output.outputs.message }}
runs:
  using: composite
  steps:
    - name: Resolve API diff inputs
      id: api_diff
      uses: actions/github-script@v8
      with:
        script: |
          // Check if we are targeting main or a stable branch
          const baseRef = context.payload.pull_request.base.ref;
          if (baseRef !== 'main' && !baseRef.endsWith('-stable')) {
            core.setOutput('changed', false);
            return;
          }

          // Check if the diff touches ReactNativeApi.d.ts
          const files = await github.paginate(github.rest.pulls.listFiles, {
            ...context.repo,
            pull_number: context.payload.pull_request.number,
          });
          const changed = files.some(f => f.filename === 'packages/react-native/ReactNativeApi.d.ts');
          core.setOutput('changed', changed);
          if (!changed) return;

          // Calculate merge base
          const {data} = await github.rest.repos.compareCommits({
            ...context.repo,
            base: context.payload.pull_request.base.ref,
            head: context.payload.pull_request.head.sha,
          });
          core.setOutput('merge_base', data.merge_base_commit.sha);

    - name: Fetch commits and extract API snapshots
      if: steps.api_diff.outputs.changed == 'true'
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
      run: |
        mkdir -p $SCRATCH_DIR
        git fetch origin "${{ steps.api_diff.outputs.merge_base }}" --depth=1
        git fetch origin "${{ github.event.pull_request.head.sha }}" --depth=1
        git show "${{ steps.api_diff.outputs.merge_base }}":packages/react-native/ReactNativeApi.d.ts > $SCRATCH_DIR/ReactNativeApi-before.d.ts \
          || echo "" > $SCRATCH_DIR/ReactNativeApi-before.d.ts
        git show "${{ github.event.pull_request.head.sha }}":packages/react-native/ReactNativeApi.d.ts > $SCRATCH_DIR/ReactNativeApi-after.d.ts \
          || echo "" > $SCRATCH_DIR/ReactNativeApi-after.d.ts

    - name: Run breaking change detection
      if: steps.api_diff.outputs.changed == 'true'
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
      run: |
        node ./scripts/js-api/diff-api-snapshot \
          $SCRATCH_DIR/ReactNativeApi-before.d.ts \
          $SCRATCH_DIR/ReactNativeApi-after.d.ts \
          > $SCRATCH_DIR/output.json

    - name: Format output message
      id: format_output
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
      run: |
        if [ ! -f "$SCRATCH_DIR/output.json" ]; then
          echo "message=" >> $GITHUB_OUTPUT
          exit 0
        fi

        RESULT=$(cat $SCRATCH_DIR/output.json | jq -r '.result // empty')
        if [ -z "$RESULT" ] || [ "$RESULT" = "NON_BREAKING" ]; then
          echo "message=" >> $GITHUB_OUTPUT
          exit 0
        fi

        # Use delimiter for multiline output
        {
          echo "message<<EOF"
          echo "> [!WARNING]"
          echo "> **JavaScript API change detected**"
          echo ">"
          echo "> This PR commits an update to \`ReactNativeApi.d.ts\`, indicating a change to React Native's public JavaScript API."
          echo ">"
          echo "> - Please include a **clear changelog message**."
          echo "> - This change will be subject to additional review."
          echo ">"
          echo "> This change was flagged as: \`${RESULT}\`"
          echo "EOF"
        } >> $GITHUB_OUTPUT