CI: Improve actions/setup workflow

.github/actions/setup/action.yml

@@ -1,24 +1,54 @@
 name: python_lib
 description: Installs the given GardenLinux Python library
+
 inputs:
-    version:
-        description: GardenLinux Python library version
-        default: "0.8.9"
+  version:
+    description: GardenLinux Python library version
+    default: "0.8.9"
+  python_version:
+    description: Python version to setup
+    default: "3.13"
+
+outputs:
+  version:
+    description: GardenLinux Python library version
+    value: ${{ inputs.version }}
+  python_version:
+    description: Python version to setup
+    value: ${{ inputs.python_version }}
+  package_tool:
+    description: "Detected Python cache strategy."
+    value: ${{ steps.env-check.outputs.package_tool }}
+
 runs:
-    using: composite
-    steps:
-        - name: Verify requirements.txt for "actions/setup-python" with enabled "pip" cache
-          shell: bash
-          run: |
-            if [ ! -f "requirements.txt" ]; then
-                echo "python-gardenlinux-lib @ git+https://github.com/gardenlinux/python-gardenlinux-lib.git@${{ inputs.version }}" | tee -a requirements.txt
-            fi
-        - name: Set up Python 3.13
-          uses: actions/setup-python@v5
-          with:
-              python-version: "3.13"
-              cache: 'pip'
-        - name: Install GardenLinux Python library
-          shell: bash
-          run: |
-              pip install git+https://github.com/gardenlinux/python-gardenlinux-lib.git@${{ inputs.version }}
+  using: composite
+  steps:
+    - name: Evaluate Python environment
+      id: env-check
+      shell: bash
+      run: |
+        # Determine cache type based on available lockfile
+        if [ -f poetry.lock ]; then
+          echo "package_tool=poetry" >> $GITHUB_OUTPUT
+        elif [ -f requirements.txt ]; then
+          echo "package_tool=pip" >> $GITHUB_OUTPUT
+        else
+          # no lockfile present: create one and use pip caching
+          echo "gardenlinux @ git+https://github.com/gardenlinux/python-gardenlinux-lib.git@${{ inputs.version }}" | tee -a requirements.txt
+          echo "package_tool=pip" >> $GITHUB_OUTPUT
+        fi
+
+    - name: Install Poetry
+      if: steps.env-check.outputs.package_tool == 'poetry'
+      uses: snok/install-poetry@v1
+
+    - name: Set up Python ${{ inputs.python_version }}
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ inputs.python_version }}
+        cache: ${{ steps.env-check.outputs.package_tool }}
+
+    - name: Install GardenLinux Python library
+      shell: bash
+      run: |
+        pip install git+https://github.com/gardenlinux/python-gardenlinux-lib.git@${{ inputs.version }}

.github/workflows/pytests.yml

@@ -11,6 +11,9 @@ jobs:
   test:
     name: Run tests and collect coverage
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python_version: [ "3.13" ]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -19,9 +22,8 @@ jobs:
 
       - name: Setup Gardenlinux
         uses: ./.github/actions/setup
-
-      - name: Install Poetry
-        uses: snok/install-poetry@v1
+        with:
+          python_version: ${{ matrix.python_version }}
 
       - name: Install dependencies
         run: poetry install --with dev
@@ -30,7 +32,7 @@ jobs:
         run: make install-test
 
       - name: Run tests
-        run: | 
+        run: |
           export GLOCI_REGISTRY_TOKEN="invalid"
           make test-coverage-ci