Add fuzz tests for frontmatter YAML parser (#3851)

Author: Copilot

.github/workflows/ci.yml

@@ -233,4 +233,6 @@ jobs:
         run: go mod verify
 
       - name: Run fuzz tests
-        run: go test -fuzz=FuzzExpressionParser -fuzztime=10s ./pkg/workflow/
+        run: |
+          go test -fuzz=FuzzParseFrontmatter -fuzztime=10s ./pkg/parser/
+          go test -fuzz=FuzzExpressionParser -fuzztime=10s ./pkg/workflow/

Makefile

@@ -71,6 +71,13 @@ bench-compare:
 	go test -bench=. -benchmem -benchtime=100x -run=^$$ ./pkg/... | tee bench_results.txt
 	@echo "Benchmark results saved to bench_results.txt"
 
+# Run fuzz tests
+.PHONY: fuzz
+fuzz:
+	@echo "Running fuzz tests for 30 seconds..."
+	go test -fuzz=FuzzParseFrontmatter -fuzztime=30s ./pkg/parser/
+	go test -fuzz=FuzzExpressionParser -fuzztime=30s ./pkg/workflow/
+
 # Test JavaScript files
 .PHONY: test-js
 test-js: build-js
@@ -278,6 +285,9 @@ help:
 	@echo "  test-js          - Run JavaScript tests"
 	@echo "  test-all         - Run all tests (Go and JavaScript)"
 	@echo "  test-coverage    - Run tests with coverage report"
+	@echo "  bench            - Run benchmarks for performance testing"
+	@echo "  bench-compare    - Run benchmarks with comparison output"
+	@echo "  fuzz             - Run fuzz tests for 30 seconds"
 	@echo "  bundle-js        - Build JavaScript bundler tool (./bundle-js <input> [output])"
 	@echo "  clean            - Clean build artifacts"
 	@echo "  deps             - Install dependencies"

pkg/parser/frontmatter.go

@@ -143,6 +143,11 @@ func ExtractFrontmatterFromContent(content string) (*FrontmatterResult, error) {
 		return nil, fmt.Errorf("failed to parse frontmatter: %w", err)
 	}
 
+	// Ensure frontmatter is never nil (yaml.Unmarshal sets it to nil for empty YAML)
+	if frontmatter == nil {
+		frontmatter = make(map[string]any)
+	}
+
 	// Extract markdown content (everything after the closing ---)
 	var markdownLines []string
 	if endIndex+1 < len(lines) {