Upload CI generated fuzz corpus coverage to codecov

Because each CI job runs on a fresh runner and can't share data between jobs. We rely on Github Actions upload-artifact and download-artifact to share the CI generated fuzz corpus, then replay them in the `contrib/generate_fuzz_coverage.sh` script to generate the coverage report.

Author: Anyitechs

.github/workflows/build.yml

@@ -110,6 +110,7 @@ jobs:
         run: CI_ENV=1 CI_MINIMIZE_DISK_USAGE=1 ./ci/ci-tx-sync-tests.sh
 
   coverage:
+    needs: fuzz
     strategy:
       fail-fast: false
     runs-on: self-hosted
@@ -133,6 +134,11 @@ jobs:
           # Maybe if codecov wasn't broken we wouldn't need to do this...
           ./codecov --verbose upload-process --disable-search --fail-on-error -f target/codecov.json -t "f421b687-4dc2-4387-ac3d-dc3b2528af57" -F 'tests'
           cargo clean
+      - name: Download honggfuzz corpus
+        uses: actions/download-artifact@v4
+        with:
+          name: hfuzz-corpus
+          path: fuzz/hfuzz_workspace
       - name: Run fuzz coverage generation
         run: |
           ./contrib/generate_fuzz_coverage.sh --output-dir `pwd` --output-codecov-json
@@ -254,6 +260,11 @@ jobs:
           cargo clean
       - name: Run fuzzers
         run: cd fuzz && ./ci-fuzz.sh && cd ..
+      - name: Upload honggfuzz corpus
+        uses: actions/upload-artifact@v4
+        with:
+          name: hfuzz-corpus
+          path: fuzz/hfuzz_workspace
 
   linting:
     runs-on: ubuntu-latest

contrib/generate_fuzz_coverage.sh

@@ -62,9 +62,50 @@ if [ "$OUTPUT_CODECOV_JSON" = "0" ]; then
     cargo llvm-cov --html --ignore-filename-regex "fuzz/" --output-dir "$OUTPUT_DIR"
     echo "Coverage report generated in $OUTPUT_DIR/html/index.html"
 else
-    cargo llvm-cov -j8 --codecov --ignore-filename-regex "fuzz/" --output-path "$OUTPUT_DIR/fuzz-codecov.json"
-    echo "Fuzz codecov report available at $OUTPUT_DIR/fuzz-codecov.json"
-fi
+    # Clean previous coverage artifacts to ensure a fresh run.
+    cargo llvm-cov clean --workspace
+
+    # Import honggfuzz corpus if the artifact was downloaded.
+    imported=0
+    if [ -d "hfuzz_workspace" ]; then
+        echo "Importing corpus from hfuzz_workspace..."
+        for target_dir in hfuzz_workspace/*; do
+            [ -d "$target_dir" ] || continue
+            src_name="$(basename "$target_dir")"
+            for dest in "$src_name" "${src_name%_target}"; do
+                mkdir -p "test_cases/$dest"
+                # Copy corpus files into the test_cases directory
+                if [ -d "$target_dir/input" ]; then
+                    find "$target_dir/input" -maxdepth 1 -type f -print0 2>/dev/null | \
+                        xargs -0 -I{} cp -n {} "test_cases/$dest/" 2>/dev/null || true
+                fi
+            done
+        done
+        # Check if any files were actually imported
+        if [ -n "$(find test_cases -type f -print -quit 2>/dev/null)" ]; then
+            imported=1
+        fi
+    fi
 
+    # Generate coverage based on whether a corpus was imported.
+    if [ "$imported" = "1" ]; then
+        echo "Replaying imported corpus to generate coverage..."
+        for corpus_dir in test_cases/*; do
+            [ -d "$corpus_dir" ] || continue
+            target_name=$(basename "$corpus_dir")
+            echo "Replaying corpus for target: $target_name"
+            cargo llvm-cov run --features libfuzzer_fuzz --bin "$target_name" -- "$corpus_dir" || true
+        done
 
+        # Merge all the raw data from the runs above into a final report.
+        echo "Generating final Codecov report from all corpus replays..."
+        cargo llvm-cov report -j8 --codecov --ignore-filename-regex "fuzz/" --output-path "$OUTPUT_DIR/fuzz-codecov.json"
 
+    else
+        # When no corpus artifact is found.
+        echo "No corpus found; generating no-corpus coverage report..."
+        cargo llvm-cov -j8 --codecov --ignore-filename-regex "fuzz/" --output-path "$OUTPUT_DIR/fuzz-codecov.json" --no-run
+    fi
+
+    echo "Fuzz codecov report available at $OUTPUT_DIR/fuzz-codecov.json"
+fi