fix(openapi-resource-mocks): sanitize FormData/File/Blob args before DOM dispatch

CustomEvent.detail is cloned via structured clone when crossing Chrome Extension
isolated worlds. FormData (and File/Blob) cannot be cloned across that boundary,
causing detail to arrive as null in the content script and throwing on destructure.

Sanitize non-cloneable args to descriptive strings in dispatchDomEvent (in-page
history retains originals for getHistory()). Also add a null guard in the content
script as a safety net for any future uncloneable type.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: constantant

tools/openapi-resource-devtools/src/content/content.ts

@@ -14,7 +14,11 @@ function send(msg: unknown): void {
 
 // ── Page → panel: relay live state-change events ─────────────────────────────
 function onMockEvent(e: Event): void {
-  const { key, event } = (e as CustomEvent<{ key: string; event: unknown }>).detail;
+  // detail is null when args contain a type that can't be structured-cloned across
+  // Chrome Extension worlds (e.g. FormData, File, Blob).
+  const detail = (e as CustomEvent<{ key: string; event: unknown } | null>).detail;
+  if (!detail) return;
+  const { key, event } = detail;
   send({ type: 'mock-event', key, event });
 }
 document.addEventListener('openapi-mock-event', onMockEvent);

tools/openapi-resource-mocks/src/lib/mock-resource-bus.ts

@@ -120,10 +120,25 @@ export class MockResourceBus {
     };
   }
 
+  private sanitizeArg(arg: unknown): unknown {
+    if (typeof FormData !== 'undefined' && arg instanceof FormData) return '[FormData]';
+    if (typeof File !== 'undefined' && arg instanceof File) return `[File: ${(arg as File).name}]`;
+    if (typeof Blob !== 'undefined' && arg instanceof Blob) return '[Blob]';
+    if (typeof ArrayBuffer !== 'undefined' && arg instanceof ArrayBuffer) return '[ArrayBuffer]';
+    return arg;
+  }
+
+  private sanitizeEventForDom(event: MockEvent): MockEvent {
+    if (event.type === 'request' || event.type === 'caught') {
+      return { ...event, args: event.args.map(a => this.sanitizeArg(a)) };
+    }
+    return event;
+  }
+
   private dispatchDomEvent(key: string, event: MockEvent): void {
     if (typeof document === 'undefined') return;
     document.dispatchEvent(
-      new CustomEvent('openapi-mock-event', { detail: { key, event } }),
+      new CustomEvent('openapi-mock-event', { detail: { key, event: this.sanitizeEventForDom(event) } }),
     );
   }