topic-commenter.yml

name: Topic PR Commenter

# this workflow is failing due to permissions problems
# until we can fix it with a better bot, i'll preserve
# the code but make it so it never matches a real path
on:
  pull_request:
    paths:
      - 'ENOSUCHPATH'

permissions:
  contents: read
  pull-requests: write

jobs:
  comment:
    runs-on: ubuntu-latest

    steps:
      - name: Comment on PR with topic info
        uses: actions/github-script@v7
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        with:
          script: |
            // Get the PR number from the event payload
            const prNumber = context.payload.pull_request.number;
            
            // List the files changed in the PR
            const { data: files } = await github.rest.pulls.listFiles({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: prNumber,
            });
            
            // Extract topics from any file changed in the "topics/" folder.
            // Assumes the file name (e.g. "python.md") indicates the topic "python"
            const topics = [];
            for (const file of files) {
              if (file.filename.startsWith('topics/')) {
                const parts = file.filename.split('/');
                const topicName = parts[parts.length - 2];
                topics.push(topicName);
              }
            }
            
            if (topics.length === 0) {
              console.log('No topics found in changed files.');
              return;
            }
            
            // Remove duplicate topic names (in case multiple files reference the same topic)
            const uniqueTopics = [...new Set(topics)];
            
            // Prepare the body of the comment
            let commentBody = '## Topic Information\n\n';
            
            for (const topic of uniqueTopics) {
              // Query the GitHub Search API for repositories with the topic.
              // Note: The Search API endpoint returns a JSON with a total_count field.
              const searchResponse = await github.request('GET /search/repositories', {
                q: `topic:${topic}`
              });
              const repoCount = searchResponse.data.total_count;
              
              // Append topic details to the comment body
              commentBody += `### ${topic}\n`;
              commentBody += `- [Topic Page](https://github.com/topics/${topic})\n`;
              commentBody += `- Repositories: ${repoCount}\n\n`;
            }
            
            // Post the comment on the PR
            await github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: prNumber,
              body: commentBody
            });