fix(export): always revoke object url on download failure

Made-with: Cursor

app/utils/markdown-export.test.ts

@@ -185,4 +185,79 @@ describe("downloadMarkdownFile", () => {
       }
     }
   });
+
+  test("still revokes object URL when anchor click throws", () => {
+    const windowDescriptor = Object.getOwnPropertyDescriptor(globalThis, "window");
+    const documentDescriptor = Object.getOwnPropertyDescriptor(globalThis, "document");
+    const urlDescriptor = Object.getOwnPropertyDescriptor(globalThis, "URL");
+
+    let revokedArg = "";
+    let removed = false;
+    const blobUrl = "blob:error-case";
+    const clickError = new Error("click failed");
+
+    const anchor = {
+      href: "",
+      download: "",
+      style: { display: "" },
+      click: () => {
+        throw clickError;
+      },
+      remove: () => {
+        removed = true;
+      },
+    };
+
+    Object.defineProperty(globalThis, "window", {
+      value: {},
+      configurable: true,
+      writable: true,
+    });
+
+    Object.defineProperty(globalThis, "document", {
+      value: {
+        createElement: (_tag: string) => anchor,
+        body: {
+          appendChild: (_node: unknown) => undefined,
+        },
+      },
+      configurable: true,
+      writable: true,
+    });
+
+    Object.defineProperty(globalThis, "URL", {
+      value: {
+        createObjectURL: (_blob: Blob) => blobUrl,
+        revokeObjectURL: (url: string) => {
+          revokedArg = url;
+        },
+      },
+      configurable: true,
+      writable: true,
+    });
+
+    try {
+      expect(() => downloadMarkdownFile("broken.md", "# broken")).toThrow("click failed");
+      expect(removed).toBe(true);
+      expect(revokedArg).toBe(blobUrl);
+    } finally {
+      if (windowDescriptor) {
+        Object.defineProperty(globalThis, "window", windowDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "window");
+      }
+
+      if (documentDescriptor) {
+        Object.defineProperty(globalThis, "document", documentDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "document");
+      }
+
+      if (urlDescriptor) {
+        Object.defineProperty(globalThis, "URL", urlDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "URL");
+      }
+    }
+  });
 });

app/utils/markdown-export.ts

@@ -36,11 +36,14 @@ export function downloadMarkdownFile(filename: string, content: string): void {
   const blob = new Blob([content], { type: "text/markdown;charset=utf-8" });
   const url = URL.createObjectURL(blob);
   const anchor = document.createElement("a");
+  try {
     anchor.href = url;
     anchor.download = filename;
     anchor.style.display = "none";
     document.body.appendChild(anchor);
     anchor.click();
+  } finally {
     anchor.remove();
     URL.revokeObjectURL(url);
   }
+}