label_pr_on_title.yml

name: Label PR based on title

on:
  workflow_run:
    workflows: ["Record PR number"]
    types:
      - completed

jobs:
  upload:
    runs-on: ubuntu-latest
    # Guardrails to only ever run if PR recording workflow was indeed
    # run in a PR event and ran successfully
    if: >
      ${{ github.event.workflow_run.event == 'pull_request' &&
      github.event.workflow_run.conclusion == 'success' }}
    steps:
      - name: 'Download artifact'
        uses: actions/github-script@v6
        # For security, we only download artifacts tied to the successful PR recording workflow
        with:
          script: |
            const fs = require('fs');

            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
               owner: context.repo.owner,
               repo: context.repo.repo,
               run_id: ${{github.event.workflow_run.id }},
            });

            const matchArtifact = artifacts.data.artifacts.filter(artifact => artifact.name == "pr")[0];

            const artifact = await github.rest.actions.downloadArtifact({
               owner: context.repo.owner,
               repo: context.repo.repo,
               artifact_id: matchArtifact.id,
               archive_format: 'zip',
            });

            fs.writeFileSync('${{github.workspace}}/pr.zip', Buffer.from(artifact.data));
      # NodeJS standard library doesn't provide ZIP capabilities; use system `unzip` command instead
      - run: unzip pr.zip

      - name: 'Label PR based on title'
        uses: actions/github-script@v6
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          # This safely runs in our base repo, not on fork
          # thus allowing us to provide a write access token to label based on PR title
          # and label PR based on semantic title accordingly
          script: |
            const fs = require('fs');
            const pr_number = Number(fs.readFileSync('./number'));
            const pr_title = fs.readFileSync('./title', 'utf-8').trim();

            const FEAT_REGEX = /feat(\((.+)\))?(\:.+)/
            const BUG_REGEX = /(fix|bug)(\((.+)\))?(\:.+)/
            const DOCS_REGEX = /(docs|doc)(\((.+)\))?(\:.+)/
            const CHORE_REGEX = /(chore)(\((.+)\))?(\:.+)/
            const DEPRECATED_REGEX = /(deprecated)(\((.+)\))?(\:.+)/
            const REFACTOR_REGEX = /(refactor)(\((.+)\))?(\:.+)/

            const labels = {
                "feature": FEAT_REGEX,
                "bug": BUG_REGEX,
                "documentation": DOCS_REGEX,
                "internal": CHORE_REGEX,
                "enhancement": REFACTOR_REGEX,
                "deprecated": DEPRECATED_REGEX,
            }

            for (const label in labels) {
                const matcher = new RegExp(labels[label])
                const isMatch = matcher.exec(pr_title)
                if (isMatch != null) {
                    console.info(`Auto-labeling PR ${pr_number} with ${label}`)

                    await github.rest.issues.addLabels({
                      issue_number: pr_number,
                      owner: context.repo.owner,
                      repo: context.repo.repo,
                      labels: [label]
                    })

                    break
                }
            }