ci: build separate CI image per python version to reduce disk usage

Author: camille-004

.github/workflows/ci.yml

@@ -48,15 +48,18 @@ jobs:
               - 'docs/**'
               - '*.md'
 
-  build-ci-image:
-    name: Build CI Image
+  build-ci-images:
+    name: Build CI Image (Python ${{ matrix.python-version }})
     runs-on: ubuntu-latest
     timeout-minutes: 30
     needs: check-changes
     if: needs.check-changes.outputs.source-changed == 'true'
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
     outputs:
-      image-tag: ${{ steps.meta.outputs.tags }}
-      image-digest: ${{ steps.build.outputs.digest }}
+      image-tag-py${{ matrix.python-version }}: ${{ steps.meta.outputs.tags }}
     steps:
       - name: Free disk space
         run: |
@@ -86,7 +89,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ghcr.io/${{ github.repository }}/ci
+          images: ghcr.io/${{ github.repository }}/ci-py${{ matrix.python-version }}
           tags: |
             type=sha,prefix={{branch}}-
 
@@ -103,9 +106,11 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          cache-from: type=gha,scope=py${{ matrix.python-version }}
+          cache-to: type=gha,mode=max,scope=py${{ matrix.python-version }}
           outputs: type=registry,compression=zstd
+          build-args: |
+            PYTHON_VERSION=${{ matrix.python-version }}
   lint:
     name: Lint
     runs-on: ubuntu-latest
@@ -136,11 +141,11 @@ jobs:
   build-wheel:
     name: Build wheel (Linux x86_64, Python ${{ matrix.python-version }})
     runs-on: ubuntu-latest
-    needs: [check-changes, build-ci-image]
+    needs: [check-changes, build-ci-images]
     if: needs.check-changes.outputs.source-changed == 'true'
     timeout-minutes: 30
     container:
-      image: ${{ needs.build-ci-image.outputs.image-tag }}
+      image: ghcr.io/${{ github.repository }}/ci-py${{ matrix.python-version }}:${{ github.ref_name }}-${{ github.sha }}
       credentials:
         username: ${{ github.actor }}
         password: ${{ secrets.GITHUB_TOKEN }}
@@ -169,11 +174,11 @@ jobs:
   build-docs:
     name: Build docs
     runs-on: ubuntu-latest
-    needs: [check-changes, build-ci-image, build-wheel]
+    needs: [check-changes, build-ci-images, build-wheel]
     if: always() && (needs.check-changes.outputs.source-changed == 'true' || needs.check-changes.outputs.docs-changed == 'true')
     timeout-minutes: 15
     container:
-      image: ${{ needs.build-ci-image.outputs.image-tag }}
+      image: ghcr.io/${{ github.repository }}/ci-py3.10:${{ github.ref_name }}-${{ github.sha }}
       credentials:
         username: ${{ github.actor }}
         password: ${{ secrets.GITHUB_TOKEN }}

Dockerfile.ci

@@ -9,7 +9,7 @@ ARG PYTHON_VERSION=3.10
 ENV PYTHON_VERSION=${PYTHON_VERSION}
 ENV DEBIAN_FRONTEND=noninteractive
 
-# Install system dependencies and Python versions in one layer with aggressive cleanup
+# Install system dependencies and specific Python version
 RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
     --mount=type=cache,target=/var/lib/apt,sharing=locked \
     apt-get update && \
@@ -18,10 +18,7 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
     add-apt-repository -y ppa:deadsnakes/ppa && \
     apt-get update && \
     apt-get install -y --no-install-recommends \
-        python3.10 python3.10-venv python3.10-dev \
-        python3.11 python3.11-venv python3.11-dev \
-        python3.12 python3.12-venv python3.12-dev \
-        python3.13 python3.13-venv python3.13-dev \
+        python${PYTHON_VERSION} python${PYTHON_VERSION}-venv python${PYTHON_VERSION}-dev \
         python3-pip && \
     rm -rf /var/lib/apt/lists/* /var/cache/apt/* /tmp/*