fix: avoid Object.assign to avoid hiding potential type errors (#1166)

Author: Uzlopak

src/types.ts

@@ -68,7 +68,10 @@ export interface State extends Options<any> {
 /**
  * Error object with optional properties coming from `octokit.request` errors
  */
-export type WebhookError = Error & Partial<RequestError>;
+export type WebhookError = Error &
+  Partial<RequestError> & {
+    event?: EmitterWebhookEventWithStringPayloadAndSignature | undefined;
+  };
 
 export interface AggregateWebhookError extends AggregateError {
   errors: WebhookError[];

src/verify-and-receive.ts

@@ -23,11 +23,12 @@ export async function verifyAndReceive(
   if (!matchesSignature) {
     const error = new Error(
       "[@octokit/webhooks] signature does not match event payload and secret",
-    );
+    ) as WebhookError;
 
-    return state.eventHandler.receive(
-      Object.assign(error, { event, status: 400 }) as WebhookError,
-    );
+    error.event = event;
+    error.status = 400;
+
+    return state.eventHandler.receive(error);
   }
 
   let payload: EmitterWebhookEvent["payload"];