Code coverage for Rust/Python (#3278)

.github/workflows/coverage.yaml

@@ -0,0 +1,41 @@
+name: Coverage
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  coverage:
+    name: Coverage for ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: ["ubuntu"]
+    runs-on: ${{ matrix.os }}-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: "3.10"
+          cache: "pip"
+          cache-dependency-path: "py-polars/build.requirements.txt"
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly-2022-04-01
+          override: true
+          profile: minimal
+          components: llvm-tools-preview
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - uses: Swatinem/rust-cache@v1
+        with:
+          key: coverage-cargo-${{ matrix.os }}
+        continue-on-error: true
+      - name: Run coverage
+        run: make coverage
+      - uses: codecov/codecov-action@v3
+        with:
+          files: coverage.lcov,coverage.xml
+          name: ${{ matrix.os }}
+          fail_ci_if_error: true

.gitignore

@@ -14,3 +14,5 @@ node_modules/
 .coverage
 venv/
 *.iml
+coverage.lcov
+coverage.xml

Makefile

@@ -7,3 +7,17 @@ changelog-rust:
 
 fmt_toml:
 	dprint fmt
+
+coverage:
+	@bash -c "\
+		rustup override set nightly-2022-04-01; \
+		source <(cargo llvm-cov show-env --export-prefix); \
+		export CARGO_TARGET_DIR=\$$CARGO_LLVM_COV_TARGET_DIR; \
+		export CARGO_INCREMENTAL=1; \
+		cargo llvm-cov clean --workspace; \
+		$(MAKE) -C py-polars venv; \
+		source py-polars/venv/bin/activate; \
+		$(MAKE) -C polars test; \
+		$(MAKE) -C py-polars test-with-cov; \
+		cargo llvm-cov --no-run --lcov --output-path coverage.lcov; \
+		"

py-polars/Makefile

@@ -28,7 +28,11 @@ test: venv
 	$(PYTHON) -m pytest tests
 
 test-with-cov: venv
-	@cd tests && ../$(PYTHON) -m pytest --cov=polars --cov-fail-under=90 --import-mode=importlib
+	@cd tests && ../$(PYTHON) -m pytest \
+		--cov=polars \
+		--cov-report xml \
+		--cov-fail-under=90 \
+		--import-mode=importlib
 
 doctest:
 	cd tests && ../$(PYTHON) run_doc_examples.py