ci: add cargo mutants weekly job

.github/workflows/cron_cargo_mutants.yml

@@ -0,0 +1,49 @@
+name: Weekly cargo-mutants
+
+permissions: {}
+
+on:
+  schedule:
+    - cron: "0 0 * * 0" # runs weekly on Sunday at 00:00
+  workflow_dispatch: # allows manual triggering
+
+jobs:
+  cargo-mutants:
+    name: Cargo Mutants
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - uses: taiki-e/install-action@2383334cf567d78771fc7d89b6b3802ef1412cf6
+        with:
+          tool: cargo-mutants
+      - run: cargo mutants --in-place --no-shuffle
+      - uses: actions/upload-artifact@v4
+        with:
+          name: mutants.out
+          path: mutants.out
+      - name: Check for new mutants
+        if: always()
+        run: |
+          if [ -s mutants.out/missed.txt ]; then
+            echo "New missed mutants found"
+            MUTANTS_VERSION=$(cargo mutants --version)
+            gh issue create \
+            --title "cargo-mutants: new mutants found" \
+            --body "$(cat <<EOF
+          Displaying up to the first 10 mutants:
+          \`\`\`
+          $(head -n 10 mutants.out/missed.txt)
+          \`\`\`
+          Running cargo mutants version: ${MUTANTS_VERSION}
+          For the complete list, please check the [mutants.out artifact](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}).
+          EOF
+          )"
+            echo "create_issue=true" >> $GITHUB_ENV
+          else
+            echo "No new mutants found"
+            echo "create_issue=false" >> $GITHUB_ENV
+          fi
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

justfile

@@ -3,6 +3,7 @@ alias c := check
 alias f := fmt
 alias t := test
 alias p := pre-push
+alias m := mutants
 
 # Build the project
 build:
@@ -26,4 +27,8 @@ test:
    cargo test --workspace --exclude 'example_*' --all-features
 
 # Run pre-push suite: format, check, and test
-pre-push: fmt check test
+pre-push: fmt check test
+
+# Run `cargo-mutants` for mutation testing
+mutants:
+   cargo mutants --in-place --no-shuffle