ci: handle min+max python version specs from pyproject.toml

Supports requires-python formats: >=3.9, >=3.9,<3.13, >=3.9,<=3.12.
Falls back to 3.x (latest stable) when no upper bound is specified.

Author: schultzp2020

.github/workflows/ci.yml

@@ -14,20 +14,27 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       min-version: ${{ steps.resolve.outputs.min }}
+      max-version: ${{ steps.resolve.outputs.max }}
       matrix: ${{ steps.resolve.outputs.matrix }}
     steps:
       - uses: actions/checkout@v4
 
       - id: resolve
         run: |
-          MIN=$(python3 -c "
-          import re
+          python3 << 'PYEOF' >> "$GITHUB_OUTPUT"
+          import re, json
           with open('pyproject.toml') as f:
-              m = re.search(r'requires-python\s*=\s*\">=(\d+\.\d+)\"', f.read())
-              print(m.group(1) if m else '3.9')
-          ")
-          echo "min=$MIN" >> "$GITHUB_OUTPUT"
-          echo "matrix=[\"$MIN\", \"3.x\"]" >> "$GITHUB_OUTPUT"
+              spec = re.search(r'requires-python\s*=\s*"([^"]+)"', f.read())
+          spec = spec.group(1) if spec else '>=3.9'
+          min_m = re.search(r'>=\s*([\d.]+)', spec)
+          max_m = re.search(r'<=?\s*([\d.]+)', spec)
+          min_v = min_m.group(1) if min_m else '3.9'
+          max_v = max_m.group(1) if max_m else '3.x'
+          matrix = [min_v, max_v] if min_v != max_v else [min_v]
+          print(f'min={min_v}')
+          print(f'max={max_v}')
+          print(f'matrix={json.dumps(matrix)}')
+          PYEOF
 
   lint:
     needs: resolve-python
@@ -41,7 +48,7 @@ jobs:
 
       - uses: actions/setup-python@v5
         with:
-          python-version: "3.x"
+          python-version: ${{ needs.resolve-python.outputs.max-version }}
 
       - run: uv sync --frozen --extra dev