fix: Fix issue where flush callback could be called twice. (#779)

Relates to #777

packages/shared/sdk-server/__tests__/LDClientImpl.events.test.ts

@@ -0,0 +1,118 @@
+import { LDClientImpl } from '../src';
+import { createBasicPlatform } from './createBasicPlatform';
+import TestLogger from './Logger';
+import makeCallbacks from './makeCallbacks';
+
+it('flushes events successfully and executes the callback', async () => {
+  const platform = createBasicPlatform();
+  platform.requests.fetch.mockImplementation(() =>
+    Promise.resolve({ status: 200, headers: new Headers() }),
+  );
+
+  const client = new LDClientImpl(
+    'sdk-key-events',
+    platform,
+    {
+      logger: new TestLogger(),
+      stream: false,
+    },
+    makeCallbacks(false),
+  );
+
+  client.identify({ key: 'user' });
+  client.variation('dev-test-flag', { key: 'user' }, false);
+
+  const flushCallback = jest.fn();
+
+  await client.flush(flushCallback);
+
+  expect(platform.requests.fetch).toHaveBeenCalledWith(
+    'https://events.launchdarkly.com/bulk',
+    expect.objectContaining({
+      method: 'POST',
+      body: expect.any(String),
+    }),
+  );
+  expect(flushCallback).toHaveBeenCalledWith(null, true);
+  expect(flushCallback).toHaveBeenCalledTimes(1);
+});
+
+it('flushes events successfully', async () => {
+  const platform = createBasicPlatform();
+  platform.requests.fetch.mockImplementation(() =>
+    Promise.resolve({ status: 200, headers: new Headers() }),
+  );
+
+  const client = new LDClientImpl(
+    'sdk-key-events',
+    platform,
+    {
+      logger: new TestLogger(),
+      stream: false,
+    },
+    makeCallbacks(false),
+  );
+
+  client.identify({ key: 'user' });
+  client.variation('dev-test-flag', { key: 'user' }, false);
+
+  await client.flush();
+
+  expect(platform.requests.fetch).toHaveBeenCalledWith(
+    'https://events.launchdarkly.com/bulk',
+    expect.objectContaining({
+      method: 'POST',
+      body: expect.any(String),
+    }),
+  );
+});
+
+it('calls error callback once when flush fails with http status code', async () => {
+  const platform = createBasicPlatform();
+  platform.requests.fetch.mockImplementation(() =>
+    Promise.resolve({ status: 401, headers: new Headers() }),
+  );
+
+  const flushCallback = jest.fn();
+  const client = new LDClientImpl(
+    'sdk-key-events',
+    platform,
+    {
+      logger: new TestLogger(),
+      stream: false,
+    },
+    makeCallbacks(false),
+  );
+
+  client.identify({ key: 'user' });
+  client.variation('dev-test-flag', { key: 'user' }, false);
+
+  await client.flush(flushCallback);
+
+  expect(flushCallback).toHaveBeenCalledWith(expect.any(Error), false);
+  expect(flushCallback).toHaveBeenCalledTimes(1);
+});
+
+it('calls error callback once when flush fails with exception', async () => {
+  const platform = createBasicPlatform();
+  platform.requests.fetch.mockImplementation(() => Promise.reject(new Error('test error')));
+
+  const flushCallback = jest.fn();
+  const client = new LDClientImpl(
+    'sdk-key-events',
+    platform,
+    {
+      logger: new TestLogger(),
+      stream: false,
+    },
+    makeCallbacks(false),
+  );
+
+  client.identify({ key: 'user' });
+  client.variation('dev-test-flag', { key: 'user' }, false);
+
+  await client.flush(flushCallback);
+
+  expect(flushCallback).toHaveBeenCalledWith(expect.any(Error), false);
+  expect(flushCallback).toHaveBeenCalledTimes(1);
+});

packages/shared/sdk-server/src/LDClientImpl.ts

@@ -773,9 +773,9 @@ export default class LDClientImpl implements LDClient {
     try {
       await this._eventProcessor.flush();
     } catch (err) {
-      callback?.(err as Error, false);
+      return callback?.(err as Error, false);
     }
-    callback?.(null, true);
+    return callback?.(null, true);
   }
 
   addHook(hook: Hook): void {