pr-build.yml

# Advisory only. This check is never marked as a required status check, and main
# has no branch protection rule referencing it. It builds and tests exactly the
# article folder(s) a PR touches -- nothing else. Folders in .github/ci-skip-folders.txt
# are filtered out before the matrix is built, so they never show up as a run,
# passing or failing (edit that file, not this one, to change what's excluded).
name: PR Build

on:
  pull_request:
    branches: [main]

# Cancel superseded runs on the same PR when new commits land.
concurrency:
  group: pr-build-${{ github.event.pull_request.number }}
  cancel-in-progress: true

permissions:
  contents: read

jobs:
  detect-changes:
    name: Detect changed article folders
    runs-on: ubuntu-latest
    outputs:
      folders: ${{ steps.compute.outputs.folders }}
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Compute changed, buildable folders
        id: compute
        shell: bash
        run: |
          set -euo pipefail

          BASE_SHA="${{ github.event.pull_request.base.sha }}"
          HEAD_SHA="${{ github.event.pull_request.head.sha }}"
          SKIP_FILE=".github/ci-skip-folders.txt"

          # Skip list: strip comments and blank lines.
          mapfile -t skip_list < <(
            sed 's/\r$//' "$SKIP_FILE" | grep -vE '^\s*#' | grep -vE '^\s*$'
          )

          is_skipped() {
            local f="$1"
            for s in "${skip_list[@]:-}"; do
              [ "$f" = "$s" ] && return 0
            done
            return 1
          }

          # Reduce every changed path to its "<category>/<article>" prefix.
          # Every article folder in this repo is exactly two levels deep.
          mapfile -t folders < <(
            git diff --name-only "$BASE_SHA" "$HEAD_SHA" \
              | awk -F/ 'NF>=2 {print $1"/"$2}' \
              | sort -u
          )

          entries="[]"
          for f in "${folders[@]:-}"; do
            [ -z "$f" ] && continue

            if is_skipped "$f"; then
              echo "::notice::Skipping '$f' -- listed in $SKIP_FILE."
              continue
            fi

            # Folder may have been deleted in this PR -- skip if no .sln remains at HEAD.
            if ! compgen -G "$f"/*.sln > /dev/null 2>&1; then
              echo "::notice::Skipping '$f' -- no .sln at HEAD (deleted or restructured)."
              continue
            fi

            entries=$(jq -c --arg folder "$f" '. + [{folder: $folder}]' <<<"$entries")
          done

          echo "folders=$entries" >> "$GITHUB_OUTPUT"
          echo "Changed, buildable folders:"
          echo "$entries" | jq .

  build-and-test:
    name: Build & test (${{ matrix.folder }})
    needs: detect-changes
    if: needs.detect-changes.outputs.folders != '[]'
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        include: ${{ fromJson(needs.detect-changes.outputs.folders) }}
    steps:
      - name: Checkout (sparse)
        uses: actions/checkout@v4
        with:
          sparse-checkout: |
            ${{ matrix.folder }}
          sparse-checkout-cone-mode: true

      - name: Setup .NET SDKs
        uses: actions/setup-dotnet@v4
        with:
          dotnet-version: |
            6.0.x
            7.0.x
            8.0.x
            9.0.x
            10.0.x

      - name: Build and test
        working-directory: ${{ matrix.folder }}
        shell: bash
        run: |
          set -euo pipefail
          sln=$(find . -maxdepth 1 -iname "*.sln" | head -n1)
          if [ -z "$sln" ]; then
            echo "::notice::No .sln found in ${{ matrix.folder }} -- skipping."
            exit 0
          fi
          echo "Building $sln"
          dotnet build "$sln" --configuration Release
          echo "Testing $sln (no-op for folders with no test project)"
          dotnet test "$sln" --configuration Release --no-build

  # Stable, folder-independent name for branch protection to require -- the
  # build-and-test job's displayed name varies with the matrix (one leg per
  # changed folder), so it can't be set as a required check directly. This
  # job always runs (even if earlier jobs are skipped) and only fails when a
  # needed job actually failed or was cancelled; an empty build matrix (a PR
  # touching no buildable folders) is a skip, not a failure, and passes here.
  ci-result:
    name: CI result
    needs: [detect-changes, build-and-test]
    if: always()
    runs-on: ubuntu-latest
    steps:
      - name: Check required jobs
        shell: bash
        run: |
          detect="${{ needs.detect-changes.result }}"
          build="${{ needs.build-and-test.result }}"
          echo "detect-changes: $detect"
          echo "build-and-test: $build"
          if [ "$detect" = "failure" ] || [ "$detect" = "cancelled" ] || [ "$build" = "failure" ] || [ "$build" = "cancelled" ]; then
            echo "A required job failed or was cancelled."
            exit 1
          fi
          echo "All required jobs passed (or were skipped)."