feat: add input validation to parseFrontmatter for non-string input

Signed-off-by: leocavalcante <leo@cavalcante.dev>

Author: leocavalcante

src/paths.d.mts

@@ -147,6 +147,7 @@ export interface ParseFrontmatterResult {
  *
  * @param content - The file content to parse
  * @returns Parse result with found status, fields, and end index
+ * @throws {TypeError} If content is not a string
  */
 export function parseFrontmatter(content: string): ParseFrontmatterResult
 

src/paths.mjs

@@ -208,8 +208,14 @@ export async function retryOnTransientError(fn, options = {}) {
  *
  * @param {string} content - The file content to parse
  * @returns {{ found: boolean, reason?: "missing" | "unclosed", fields: Record<string, string>, endIndex: number }} Parse result
+ * @throws {TypeError} If content is not a string
  */
 export function parseFrontmatter(content) {
+	if (typeof content !== "string") {
+		throw new TypeError(
+			`parseFrontmatter: content must be a string, got ${content === null ? "null" : typeof content}`,
+		)
+	}
 	// Frontmatter must start at the beginning of the file
 	if (!content.startsWith("---")) {
 		return { found: false, reason: "missing", fields: {}, endIndex: 0 }

tests/paths.test.ts

@@ -613,6 +613,48 @@ url: https://example.com
 			const result = parseFrontmatter(content)
 			expect(result.fields.url).toBe("https://example.com")
 		})
+
+		it("should throw TypeError for null input", () => {
+			expect(() => parseFrontmatter(null as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter(null as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got null",
+			)
+		})
+
+		it("should throw TypeError for undefined input", () => {
+			expect(() => parseFrontmatter(undefined as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter(undefined as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got undefined",
+			)
+		})
+
+		it("should throw TypeError for number input", () => {
+			expect(() => parseFrontmatter(123 as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter(123 as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got number",
+			)
+		})
+
+		it("should throw TypeError for object input", () => {
+			expect(() => parseFrontmatter({} as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter({} as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got object",
+			)
+		})
+
+		it("should throw TypeError for array input", () => {
+			expect(() => parseFrontmatter([] as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter([] as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got object",
+			)
+		})
+
+		it("should throw TypeError for boolean input", () => {
+			expect(() => parseFrontmatter(true as unknown as string)).toThrow(TypeError)
+			expect(() => parseFrontmatter(true as unknown as string)).toThrow(
+				"parseFrontmatter: content must be a string, got boolean",
+			)
+		})
 	})
 
 	describe("validateAgentContent", () => {