experiment.yaml

name: Next-Gen CI Prototype

on:
  pull_request:
    branches: [ main ]

# 1. CONCURRENCY: Stop burning money on abandoned commits
concurrency:
  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
  cancel-in-progress: true

jobs:
  # 2. DISCOVERY: Find exactly what changed and output JSON
  discover:
    runs-on: ubuntu-latest
    outputs:
      packages: ${{ steps.set-matrix.outputs.packages }}
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0 # Needed to diff against main

      - name: Calculate Changed Packages
        id: set-matrix
        run: |
          # Find all modified directories inside packages/
          CHANGED=$(git diff --name-only origin/main...HEAD | grep "^packages/" | cut -d/ -f2 | sort -u || true)
          
          if [ -z "$CHANGED" ]; then
            echo "packages=[]" >> $GITHUB_OUTPUT
            exit 0
          fi
          
          # Convert bash list to JSON array using jq
          JSON_ARRAY=$(jq -R -s -c 'split("\n")[:-1]' <<< "$CHANGED")
          echo "Discovered packages: $JSON_ARRAY"
          echo "packages=$JSON_ARRAY" >> $GITHUB_OUTPUT

  # 3. EXECUTION: Native Fan-out Matrix
  unit-test:
    needs: discover
    if: ${{ needs.discover.outputs.packages != '[]' }}
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false # Don't kill the whole matrix if one package fails
      matrix:
        package: ${{ fromJSON(needs.discover.outputs.packages) }}
        # Risk-Tiering: Smoke test on presubmit to save money
        python: ["3.11"] 
    
    steps:
      - uses: actions/checkout@v4

      # 4. THE ENGINE SWAP: Rust-based uv instead of setup-python + pip
      - name: Install uv and Python
        uses: astral-sh/setup-uv@v5
        with:
          python-version: ${{ matrix.python }}
          enable-cache: true
          cache-dependency-glob: "packages/${{ matrix.package }}/setup.py"

      - name: Execute Tests (High-Density)
        # uvx downloads and runs nox in milliseconds without a global pip install
        run: |
          cd packages/${{ matrix.package }}
          
          # Force nox to use uv as its backend for lightning-fast venv creation
          export VIRTUALENV_CREATOR=uv
          
          echo "Running targeted tests for ${{ matrix.package }} on Python ${{ matrix.python }}"
          uvx nox -s unit-${{ matrix.python }}