action: use the most recent python from tool cache to run the GitHub …

…Action

.github/workflows/test.yml

@@ -66,6 +66,19 @@ jobs:
         name: sample_wheels
         path: wheelhouse
 
+    - name: Get some sample wheels (GitHub Action)
+      uses: ./
+      with:
+        package-dir: sample_proj
+        output-dir: wheelhouse_action
+      env:
+        CIBW_ARCHS_MACOS: x86_64 universal2 arm64
+
+    - uses: actions/upload-artifact@v3
+      with:
+        name: sample_wheels_action
+        path: wheelhouse_action
+
     - name: Test cibuildwheel
       run: |
         python ./bin/run_tests.py

action.yml

@@ -20,10 +20,52 @@ branding:
 runs:
   using: composite
   steps:
+    # Set up a non-EOL, cibuildwheel & pipx supported Python version
+    - name: Find python interpreter
+      id: python
+      run: |
+        from pathlib import Path
+        import os
+        import platform
+        import sys
+
+        SUPPORTED_VERSIONS=("3.10", "3.9", "3.8", "3.7", "3.6")
+        EXT = "${{ runner.os == 'Windows' && '.exe' || '3' }}"
+        PREFIX = "${{ runner.os != 'Windows' && 'bin/' || '' }}"
+        ARCH_MAP = {"AMD64": "x64", "x86_64": "x64"}
+
+        arch = ARCH_MAP.get(platform.machine(), None)
+        base_path = Path(os.environ.get("RUNNER_TOOL_CACHE", "not_existing")) / "Python"
+        if arch and base_path.exists():
+            for version in SUPPORTED_VERSIONS:
+                pattern = "{}.*/{}/{}python{}".format(version, arch, PREFIX, EXT)
+                matches = list(base_path.glob(pattern))
+                if matches:
+                    exact_version = matches[0].relative_to(base_path).parts[0]
+                    print("Using cached CPython {} at {}".format(exact_version, matches[0]))
+                    print("::set-output name=interpreter-path::{}".format(matches[0]))
+                    exit(0)
+        # fallback
+        print("::warning ::Couldn't find a suitable python version in the toolcache, fallback to current interpreter")
+        current_version = ".".join(map(str, sys.version_info[:2]))
+        if current_version in SUPPORTED_VERSIONS:
+            exact_version = ".".join(map(str, sys.version_info[:3]))
+            print("Using Python {} at {}".format(exact_version, sys.executable))
+            print("::set-output name=interpreter-path::{}".format(sys.executable))
+            exit(0)
+        print(
+            "::error ::The current interpreter is Python {}, cibuildwheel requires one of {}.".format(
+                current_version, ", ".join(SUPPORTED_VERSIONS)
+            ),
+            "You can use actions/setup-python to install a supported version."
+        )
+        exit(1)
+      shell: "python3 {0}"
 
     # Redirecting stderr to stdout to fix interleaving issue in Actions.
     - run: >
         pipx run
+        --python '${{ steps.python.outputs.interpreter-path }}'
         --spec '${{ github.action_path }}'
         cibuildwheel
         ${{ inputs.package-dir }}