fix(.github/workflows): add coverage reporting to all workflows (#4699)

Our code coverage appeared low because not all test results were being
uploaded to Codecov.

The language-specific CI workflows were running tests but not collecting
or uploading coverage. This change adds coverage flags to go test and
uploads coverage from each language workflow so Codecov can correctly
merge results from the tests that actually run.

For #4664

Author: julieqiu

.github/workflows/dart.yaml

@@ -39,4 +39,8 @@ jobs:
       - name: Run internal/sidekick/dart tests
         run: go test -race ./internal/sidekick/dart
       - name: Run internal/librarian/dart tests
-        run: go test -race ./internal/librarian/dart
+        run: go test -race -coverprofile=coverage.out -covermode=atomic ./internal/librarian/dart
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/java.yaml

@@ -45,4 +45,8 @@ jobs:
           test -x "$(which protoc-gen-java_grpc)"
           test -x "$(which protoc-gen-java_gapic)"
       - name: Run internal/librarian/java tests
-        run: go test -race ./internal/librarian/java
+        run: go test -race -coverprofile=coverage.out -covermode=atomic ./internal/librarian/java
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/nodejs.yaml

@@ -53,4 +53,8 @@ jobs:
         run: |
           pip install gcp-synthtool@git+https://github.com/googleapis/synthtool@5aa438a342707842d11fbbb302c6277fbf9e4655
       - name: Run internal/librarian/nodejs tests
-        run: go test -race ./internal/librarian/nodejs
+        run: go test -race -coverprofile=coverage.out -covermode=atomic ./internal/librarian/nodejs
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/python.yaml

@@ -54,4 +54,8 @@ jobs:
       - name: Verify git is available
         run: git --version
       - name: Run internal/librarian/python tests
-        run: go test -race ./internal/librarian/python
+        run: go test -race -coverprofile=coverage.out -covermode=atomic ./internal/librarian/python
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}

.github/workflows/rust.yaml

@@ -43,7 +43,11 @@ jobs:
       - name: Run sidekick tests
         run: go test -race ./internal/sidekick/...
       - name: Run internal/librarian/rust tests
-        run: go test -race ./internal/librarian/rust
+        run: go test -race -coverprofile=coverage.out -covermode=atomic ./internal/librarian/rust
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
   integration:
     runs-on: ubuntu-24.04
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'