rw-preview-label.yml

name: Update Preview Label

# Ensure that only this Pull Request has the preview label.

on:
  workflow_call:

jobs:
  preview_labels:
    name: Update preview labels
    runs-on: ubuntu-latest

    steps:
    - name: Remove preview label from all other PRs
      uses: actions/github-script@v7
      with:
        script: |
          const issues = await github.rest.issues.listForRepo({
            owner: context.repo.owner,
            repo: context.repo.repo,
            labels: 'preview',
          });

          for (const issue of issues.data) {
            if (issue.number === context.issue.number) continue;
            if (!issue.pull_request) continue;

            console.log(`Removing label from #${issue.number}`);

            await github.rest.issues.removeLabel({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: issue.number,
              name: 'preview',
            });
          }

    # When two PRs get the Preview label before they can execute, the first will
    # remove the label from the second, and the second from the first. This would
    # leave no PR with a Preview label. So always make sure that if we finish,
    # our PR has a preview label. As by concurrency one PR always finishes last,
    # the last one is now guaranteed to have a preview label.
    - name: Ensure we have a preview label
      uses: actions/github-script@v7
      with:
        script: |
          await github.rest.issues.addLabels({
            owner: context.repo.owner,
            repo: context.repo.repo,
            issue_number: context.issue.number,
            labels: ['preview'],
          });