test: add coverage for rust test (TabbyML#1411)

* add rust coverage

* add coverage

* update

* update

.github/workflows/test-rust.yml

@@ -24,6 +24,7 @@ jobs:
   tests:
     runs-on: ubuntu-latest
     env:
+      CARGO_TERM_COLOR: always
       SCCACHE_GHA_ENABLED: true
       RUSTC_WRAPPER: sccache
       CARGO_INCREMENTAL: 0
@@ -60,3 +61,50 @@ jobs:
 
       - name: Run unit tests
         run: cargo test --bin tabby --lib
+
+  coverage:
+    runs-on: ubuntu-latest
+    env:
+      CARGO_TERM_COLOR: always
+      SCCACHE_GHA_ENABLED: true
+      RUSTC_WRAPPER: sccache
+      CARGO_INCREMENTAL: 0
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ env.RUST_TOOLCHAIN }}
+
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+
+      - name: Sccache cache
+        uses: mozilla-actions/[email protected]
+        with:
+          version: "v0.4.0"
+
+      - name: Cargo registry cache
+        uses: actions/cache@v3
+        with:
+          key: cargo-${{ runner.os }}-${{ hashFiles('**/Cargo.toml') }}-${{ github.sha }}
+          restore-keys: |
+            cargo-${{ runner.os }}-${{ hashFiles('**/Cargo.toml') }}-
+            cargo-${{ runner.os }}-
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+
+      - run: bash ./ci/prepare_build_environment.sh
+
+      - name: Generate code coverage
+        run: cargo llvm-cov --bin tabby --lib --lcov --output-path lcov.info
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          files: lcov.info
+          fail_ci_if_error: true