feat(coverage): Reduce coverage false-negatives using grcov

Previously, we would report some tag style macros such as
`#[repr(packed)]` as being uncovered.

We are now also including doctests in our coverage reports.

Finally, a new script `coverage_report.sh` makes coverage checking
easier.

.github/workflows/qc.yaml

@@ -194,19 +194,17 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - run: rustup default nightly
       - run: rustup component add llvm-tools-preview
       - run: |
           cargo install cargo-llvm-cov || true
-          cargo llvm-cov \
-            --workspace\
-            --all-features \
-            --lcov \
-            --output-path coverage.lcov
+          cargo install grcov || true
+          ./coverage_report.sh
       # If using tarapulin
       #- run: cargo install cargo-tarpaulin
       #- run: cargo tarpaulin --out Xml
       - name: Upload coverage reports to Codecov
         uses: codecov/codecov-action@v5
         with:
-          files: ./coverage.lcov
+          files: ./target/grcov/lcov
           verbose: true

CONTRIBUTING.md

@@ -23,5 +23,5 @@ RUST_MIN_STACK=8388608 cargo test --workspace --all-features
 Keep in mind that many of Rosenpass' tests are doctests, so to get an accurate read on our code coverage, you have to include doctests:
 
 ```bash
-cargo llvm-cov --all-features --workspace --doctests --html --open
+./coverage_report.sh
 ```

coverage_report.sh

@@ -0,0 +1,44 @@
+#! /usr/bin/env bash
+
+set -e -o pipefail
+
+OUTPUT_DIR="target/grcov"
+
+log() {
+  echo >&2 "$@"
+}
+
+exc() {
+  echo '$' "$@"
+  "$@"
+}
+
+main() {
+  exc cd "$(dirname "$0")"
+
+  local open="0"
+  if [[ "$1" == "--open" ]]; then
+    open="1"
+  fi
+
+  exc cargo llvm-cov --all-features --workspace --doctests
+
+  exc rm -rf "${OUTPUT_DIR}"
+  exc mkdir -p "${OUTPUT_DIR}"
+  exc grcov target/llvm-cov-target/ --llvm  -s . --branch \
+    --binary-path ./target/llvm-cov-target/debug/deps \
+    --ignore-not-existing --ignore '../*' --ignore "/*" \
+    --excl-line '^\s*#\[(derive|repr)\(' \
+    -t lcov,html,markdown -o "${OUTPUT_DIR}"
+
+  if (( "${open}" == 1 )); then
+    xdg-open "${PWD}/${OUTPUT_DIR}/html/index.html"
+  fi
+
+  log ""
+  log "Generated reports in \"${PWD}/${OUTPUT_DIR}\"."
+  log "Open \"${PWD}/${OUTPUT_DIR}/html/index.html\" to view HTML report."
+  log ""
+}
+
+main "$@"

flake.nix

@@ -121,6 +121,7 @@
               proverif-patched
               inputs.fenix.packages.${system}.complete.toolchain
               pkgs.cargo-llvm-cov
+              pkgs.grcov
             ];
           };
           devShells.coverage = pkgs.mkShell {
@@ -128,6 +129,7 @@
             nativeBuildInputs = [
               inputs.fenix.packages.${system}.complete.toolchain
               pkgs.cargo-llvm-cov
+              pkgs.grcov
             ];
           };