perf: optimize extractWorkflowNameFromFile by eliminating unnecessary YAML parse (#21012)

* Initial plan

* perf: optimize extractWorkflowNameFromFile to skip YAML parsing

Co-authored-by: pelikhan <[email protected]>

* refactor: extract fastParseTitle function and add tests

Co-authored-by: pelikhan <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: pelikhan <[email protected]>
Co-authored-by: Peli de Halleux <[email protected]>

Author: Copilot

pkg/cli/commands_utils_test.go

@@ -113,6 +113,113 @@ func TestExtractWorkflowNameFromFile_NonExistentFile(t *testing.T) {
 	}
 }
 
+func TestFastParseTitle(t *testing.T) {
+	tests := []struct {
+		name        string
+		content     string
+		expected    string
+		expectError bool
+	}{
+		{
+			name: "H1 after frontmatter",
+			content: `---
+title: Test
+---
+
+# My Workflow Title
+
+Some content.`,
+			expected: "My Workflow Title",
+		},
+		{
+			name: "H1 with trailing spaces",
+			content: `---
+engine: copilot
+---
+
+# Weekly Research   
+
+Content here.`,
+			expected: "Weekly Research",
+		},
+		{
+			name: "H1 without frontmatter",
+			content: `# Simple Title
+
+No frontmatter here.`,
+			expected: "Simple Title",
+		},
+		{
+			name:     "H1 is first line (no frontmatter)",
+			content:  `# Inline Title`,
+			expected: "Inline Title",
+		},
+		{
+			name:     "no H1 header",
+			content:  "Just some text without headers.",
+			expected: "",
+		},
+		{
+			name: "only H2 headers",
+			content: `---
+engine: copilot
+---
+
+## Not an H1`,
+			expected: "",
+		},
+		{
+			name:     "empty content",
+			content:  "",
+			expected: "",
+		},
+		{
+			name: "unclosed frontmatter returns error",
+			content: `---
+title: Oops
+`,
+			expectError: true,
+		},
+		{
+			name: "dash in middle of content is not frontmatter",
+			content: `Some text
+
+---
+
+# Not Skipped`,
+			expected: "Not Skipped",
+		},
+		{
+			name: "H1 inside frontmatter is ignored",
+			content: `---
+# not a header
+---
+
+# Real Title`,
+			expected: "Real Title",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := fastParseTitle(tt.content)
+			if tt.expectError {
+				if err == nil {
+					t.Errorf("fastParseTitle(%q) expected error, got nil", tt.content)
+				}
+				return
+			}
+			if err != nil {
+				t.Errorf("fastParseTitle(%q) unexpected error: %v", tt.content, err)
+				return
+			}
+			if got != tt.expected {
+				t.Errorf("fastParseTitle(%q) = %q, want %q", tt.content, got, tt.expected)
+			}
+		})
+	}
+}
+
 func TestIsGitRepo(t *testing.T) {
 	// Test in current directory (should be a git repo based on project setup)
 	result := isGitRepo()

pkg/cli/workflows.go

@@ -282,26 +282,59 @@ func getMarkdownWorkflowFiles(workflowDir string) ([]string, error) {
 	return mdFiles, nil
 }
 
+// fastParseTitle scans markdown content for the first H1 header, skipping an
+// optional frontmatter block, without performing a full YAML parse.
+//
+// Frontmatter is recognised only when "---" appears on the very first line
+// (matching the behaviour of ExtractFrontmatterFromContent). Returns the H1
+// title text, or ("", nil) when no H1 header is present. Returns an error if
+// frontmatter is opened but never closed.
+func fastParseTitle(content string) (string, error) {
+	firstLine := true
+	inFrontmatter := false
+	pastFrontmatter := false
+	for line := range strings.SplitSeq(content, "\n") {
+		trimmed := strings.TrimSpace(line)
+		if firstLine {
+			firstLine = false
+			if trimmed == "---" {
+				inFrontmatter = true
+				continue
+			}
+			// No frontmatter on first line; treat the entire file as markdown.
+			pastFrontmatter = true
+		} else if inFrontmatter && !pastFrontmatter {
+			if trimmed == "---" {
+				pastFrontmatter = true
+			}
+			continue
+		}
+		if pastFrontmatter && strings.HasPrefix(trimmed, "# ") {
+			return strings.TrimSpace(trimmed[2:]), nil
+		}
+	}
+
+	// Unclosed frontmatter is an error (consistent with ExtractFrontmatterFromContent).
+	if inFrontmatter && !pastFrontmatter {
+		return "", errors.New("frontmatter not properly closed")
+	}
+
+	return "", nil
+}
+
 // extractWorkflowNameFromFile extracts the workflow name from a file's H1 header
 func extractWorkflowNameFromFile(filePath string) (string, error) {
 	content, err := os.ReadFile(filePath)
 	if err != nil {
 		return "", err
 	}
 
-	// Extract markdown content (excluding frontmatter)
-	result, err := parser.ExtractFrontmatterFromContent(string(content))
+	title, err := fastParseTitle(string(content))
 	if err != nil {
 		return "", err
 	}
-
-	// Look for first H1 header
-	lines := strings.SplitSeq(result.Markdown, "\n")
-	for line := range lines {
-		line = strings.TrimSpace(line)
-		if strings.HasPrefix(line, "# ") {
-			return strings.TrimSpace(line[2:]), nil
-		}
+	if title != "" {
+		return title, nil
 	}
 
 	// No H1 header found, generate default name from filename