feat(launchdarkly-client-provider): Add tracking API (#1219)

Signed-off-by: Tommy Josépovic <[email protected]>

Author: tjosepo

libs/providers/launchdarkly-client/README.md

@@ -59,6 +59,16 @@ await OpenFeature.setContext({ key: 'my-key' });
 
 Read more about LD contexts [here](https://launchdarkly.github.io/js-client-sdk/interfaces/LDContextCommon.html)
 
+## Tracking
+
+You can send custom events to LaunchDarkly metrics for use in
+experiments and guarded rollouts. To learn more, read [Sending custom events](https://launchdarkly.com/docs/sdk/features/events).
+
+```ts
+const client = await OpenFeature.getClient();
+client.track('event-key-123abc', { customProperty: someValue })
+```
+
 ## Building
 
 Run `nx package providers-launchdarkly-client` to build the library.

libs/providers/launchdarkly-client/src/lib/launchdarkly-client-provider.spec.ts

@@ -27,6 +27,7 @@ describe('LaunchDarklyClientProvider', () => {
     waitForInitialization: jest.fn(),
     on: jest.fn(),
     close: jest.fn(),
+    track: jest.fn(),
   } as unknown as jest.Mocked<LDClient>;
 
   beforeAll(() => {
@@ -376,6 +377,18 @@ describe('LaunchDarklyClientProvider', () => {
     });
   });
 
+  it('calls the client track method properly', async () => {
+    ldClientMock.track = jest.fn().mockResolvedValue({});
+    ofClient.track('event-key-123abc', { value: 99.77, currency: 'USD' });
+    expect(ldClientMock.track).toHaveBeenCalledWith('event-key-123abc', { currency: 'USD' }, 99.77);
+
+    ofClient.track('event-key-123abc', { value: 99.77 });
+    expect(ldClientMock.track).toHaveBeenCalledWith('event-key-123abc', {}, 99.77);
+
+    ofClient.track('event-key-123abc', { currency: 'USD' });
+    expect(ldClientMock.track).toHaveBeenCalledWith('event-key-123abc', { currency: 'USD' }, undefined);
+  });
+
   describe('onContextChange', () => {
     it('logs information about missing keys', async () => {
       ldClientMock.identify = jest.fn().mockResolvedValue({});

libs/providers/launchdarkly-client/src/lib/launchdarkly-client-provider.ts

@@ -11,6 +11,7 @@ import {
   OpenFeatureEventEmitter,
   ProviderEvents,
   ProviderStatus,
+  TrackingEventDetails,
 } from '@openfeature/web-sdk';
 
 import isEmpty from 'lodash.isempty';
@@ -153,6 +154,11 @@ export class LaunchDarklyClientProvider implements Provider {
     return wrongTypeResult(defaultValue);
   }
 
+  track(trackingEventName: string, _context: EvaluationContext, { value, ...details }: TrackingEventDetails): void {
+    // The LD Client already has the context form the identify method, so we can omit it here.
+    this.client.track(trackingEventName, details, value);
+  }
+
   private translateContext(context: EvaluationContext) {
     return translateContext(this.logger, context);
   }