labels.yml

name: Apply PR Labels

# workflow_run is used intentionally here: the elevated-permission step runs
# in the base-repo context but never checks out PR code, so it is safe.
on:
  workflow_run: # zizmor: ignore[dangerous-triggers]
    workflows: ["Labels Trigger"]
    types:
      - completed

permissions: {}

concurrency:
  group: labels-apply-${{ github.event.workflow_run.id }}
  cancel-in-progress: true

jobs:
  labels-by-language:
    name: labels-by-language
    runs-on: ubuntu-slim
    if: github.event.workflow_run.conclusion == 'success'
    permissions:
      pull-requests: write  # So we can add labels to the pull request
    steps:
      - uses: actions/github-script@v9
        with:
          script: |
            // For same-repo PRs the pull_requests array is populated directly.
            // For fork PRs it is empty, so fall back to a commit-SHA lookup.
            let prNumber;

            const prs = context.payload.workflow_run.pull_requests;
            if (prs && prs.length > 0) {
              prNumber = prs[0].number;
            } else {
              // For fork PRs, commits don't exist in the base repo history so
              // listPullRequestsAssociatedWithCommit returns empty. Use the
              // head owner + branch from the workflow_run payload instead.
              const headOwner = context.payload.workflow_run.head_repository.owner.login;
              const headBranch = context.payload.workflow_run.head_branch;
              const result = await github.rest.pulls.list({
                owner: context.repo.owner,
                repo: context.repo.repo,
                head: `${headOwner}:${headBranch}`,
                state: 'open',
              });
              if (result.data.length === 0) {
                core.warning(`No open PR found for ${headOwner}:${headBranch}`);
                return;
              }
              prNumber = result.data[0].number;
            }

            const filenames = (await github.paginate(github.rest.pulls.listFiles, {
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: prNumber,
              per_page: 100,
            })).map(file => file.filename);
            console.log(filenames);

            const vehicle_labels = {
              AntennaTracker: 'AntennaTracker',
              ArduCopter: 'Copter',
              ArduPlane: 'Plane',
              ArduSub: 'Sub',
              Blimp: 'Blimp',
              Rover: 'Rover',
            };

            const vehicle_sim_labels = {
              Helicopter: 'TradHeli',
              QuadPlane: 'VTOL-Plane',
              Sailboat: 'Sailboat',
              Blimp: 'Blimp',
              Plane: 'Plane',
              Rover: 'Rover',
              Submarine: 'Sub',
            };

            const generic_suffix_labels = {
              '.lua': 'Scripting',
              '.py': 'Python',
            };

            const generic_prefix_labels = {
              'libraries/AP_ExternalAHRS': 'ExternalAHRS',
              'libraries/AP_Compass': 'Compass',
              'libraries/AP_NavEKF': 'EKF',
              'libraries/AP_HAL_Linux': 'Linux',
              'libraries/GCS_MAVLink': 'MAVLink',
              'libraries/SITL': 'SITL',
              'Tools/AP_Periph': 'AP_Periph',
              'Tools/autotest': 'CI',
              '.github/workflows': 'github_actions',
            };

            const specific_vehicle_checks = {
              'VTOL-Plane': ['ArduPlane/quadplane'],
              'TradHeli': [
                'ArduCopter/heli.cpp',
                'Tools/autotest/default_params/copter-heli',
                'libraries/AP_Motors/AP_MotorsHeli',
              ],
              'Sailboat': ['Rover/sailboat'],
              'Sub': ['libraries/AP_Motors/AP_Motors6DOF'],
            };

            const labels = new Set();
            for (const filename of filenames) {
              // Generic checks
              for (const [suffix, label] of Object.entries(generic_suffix_labels)) {
                if (filename.endsWith(suffix)) {
                  labels.add(label);
                  break;
                }
              }
              for (const [prefix, label] of Object.entries(generic_prefix_labels)) {
                if (filename.startsWith(prefix)) {
                  labels.add(label);
                  break;
                }
              }

              // Specific/niche vehicle checks
              var specific = false;  // There can only be one specific label per file.
              for (const [vehicle, prefixes] of Object.entries(specific_vehicle_checks)) {
                for (const prefix of prefixes) {
                  if (filename.startsWith(prefix)) {
                    labels.add(vehicle);
                    specific = true;
                    break;
                  }
                }
                if (specific) break;
              }

              if (specific) continue;
              
              for (const [vehicle, label] of Object.entries(vehicle_sim_labels)) {
                if (
                  filename === `Tools/autotest/${vehicle.toLowerCase()}.py` ||
                  filename.startsWith(`Tools/autotest/default_params/${vehicle.toLowerCase()}`) ||
                  filename.startsWith(`libraries/SITL/SIM_${vehicle}`)
                ) {
                  labels.add(label);
                  specific = true;
                  break;
                }
              }

              if (specific) continue;

              // General vehicle checks
              for (const [vehicle, label] of Object.entries(vehicle_labels)) {
                if (
                  filename.startsWith(vehicle) ||
                  filename.startsWith(`Tools/autotest/${vehicle}_Test`) ||
                  filename === `Tools/autotest/${vehicle.toLowerCase()}.py`
                ) {
                  labels.add(label);
                  break;
                }
              }
            }
            console.log(labels);

            if (labels.size > 0) {
              github.rest.issues.addLabels({
                issue_number: prNumber,
                owner: context.repo.owner,
                repo: context.repo.repo,
                labels: Array.from(labels),
              });
            }