fix(google-pubsub): Wrap Google SDK errors with helpful errors

src/lib/googlePubSub.spec.ts

@@ -2,11 +2,11 @@ import { jest } from '@jest/globals';
 import type { CloudEvent } from 'cloudevents';
 import { formatISO, getUnixTime, setMilliseconds } from 'date-fns';
 
-import { mockSpy } from '../testUtils/jest.js';
+import { getPromiseRejection, mockSpy } from '../testUtils/jest.js';
 import { GOOGLE_PUBSUB_TOPIC, EVENT } from '../testUtils/stubs.js';
 import { jsonSerialise } from '../testUtils/json.js';
 
-const mockPublishMessage = mockSpy(jest.fn<any>().mockResolvedValue(undefined));
+const mockPublishMessage = mockSpy(jest.fn<any>());
 const mockTopic = jest.fn<any>().mockReturnValue({ publishMessage: mockPublishMessage });
 jest.unstable_mockModule('@google-cloud/pubsub', () => ({
   // eslint-disable-next-line @typescript-eslint/naming-convention
@@ -209,6 +209,21 @@ describe('makeGooglePubSubEmitter', () => {
 
     expect(mockTopic).toHaveBeenCalledWith(GOOGLE_PUBSUB_TOPIC);
   });
+
+  test('Publish errors should be wrapped', async () => {
+    const error = new Error('Publish error');
+    mockPublishMessage.mockRejectedValue(error);
+
+    const errorWrapper = await getPromiseRejection(
+      async () => makeGooglePubSubEmitter(GOOGLE_PUBSUB_TOPIC)(EVENT),
+      Error,
+    );
+
+    expect(errorWrapper.message).toBe(
+      `Failed to publish message to Google PubSub topic "${GOOGLE_PUBSUB_TOPIC}"`,
+    );
+    expect(errorWrapper.cause).toBe(error);
+  });
 });
 
 describe('convertGooglePubSubMessage', () => {

src/lib/googlePubSub.ts

@@ -110,7 +110,14 @@ export function makeGooglePubSubEmitter(topicName: string): EmitterFunction {
   return async (event) => {
     const topic = CLIENT.topic(topicName);
     const message = convertEventToMessage(event);
-    await topic.publishMessage(message);
+    try {
+      await topic.publishMessage(message);
+    } catch (err) {
+      // Google SDK exceptions are utterly meaningless
+      throw new Error(`Failed to publish message to Google PubSub topic "${topicName}"`, {
+        cause: err,
+      });
+    }
   };
 }
 

src/testUtils/jest.ts

@@ -20,3 +20,18 @@ export function mockSpy<
 export function getMockInstance(mockedObject: any): jest.MockInstance<any, any> {
   return mockedObject as unknown as jest.MockInstance<any, any>;
 }
+
+export async function getPromiseRejection<ErrorType extends Error>(
+  rejectingFunction: () => Promise<unknown>,
+  expectedErrorType: new () => ErrorType,
+): Promise<ErrorType> {
+  let error: ErrorType | undefined;
+  try {
+    await rejectingFunction();
+  } catch (err) {
+    error = err as ErrorType;
+  }
+
+  expect(error).toBeInstanceOf(expectedErrorType);
+  return error!;
+}