feat: OpenFeature Tracking Support (#52)

**Requirements**

- [x] I have added test coverage for new or changed functionality
- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [x] I have validated my changes against all supported platform
versions

**Related issues**

https://launchdarkly.atlassian.net/browse/SDK-1117

**Describe the solution you've provided**

Implemented OpenFeature Provider method `track()` in
LaunchDarklyProvider. It makes a call under the hood to
`LDClient.track()`. The `value` attribute will be pulled out of the
TrackingEventDetails param and passed to `LDClient.track()` as
metricValue. The remaining object (without value) will be passed to
`LDClient.track()` as data. If the remaining object is empty then
undefined will be passed.

**Describe alternatives you've considered**

N/A

**Additional context**

N/A

Author: abarker-launchdarkly

CONTRIBUTING.md

@@ -14,7 +14,7 @@ We encourage pull requests and other contributions from the community. Before su
 
 ### Prerequisites
 
-The project should be built and tested against the lowest compatible version, Node 16. It uses `npm`, which is bundled in all supported versions of Node.
+The project should be built and tested against the lowest compatible version, Node 18. It uses `npm`, which is bundled in all supported versions of Node.
 
 ### Setup
 

__tests__/LaunchDarklyProvider.test.ts

@@ -326,4 +326,54 @@ describe('given a mock LaunchDarkly client', () => {
     expect(logger.logs[0]).toEqual("The EvaluationContext contained both a 'targetingKey' and a"
     + " 'key' attribute. The 'key' attribute will be discarded.");
   });
+
+  it('handles tracking with invalid context', () => {
+    ofClient.track('test-event', {});
+    expect(logger.logs[0]).toEqual("The EvaluationContext must contain either a 'targetingKey' "
+      + "or a 'key' and the type must be a string.");
+  });
+
+  it('handles tracking with no data or metricValue', () => {
+    ldClient.track = jest.fn();
+    ofClient.track('test-event', basicContext);
+    expect(ldClient.track).toHaveBeenCalledWith(
+      'test-event',
+      translateContext(logger, basicContext),
+      undefined,
+      undefined,
+    );
+  });
+
+  it('handles tracking with only metricValue', () => {
+    ldClient.track = jest.fn();
+    ofClient.track('test-event', basicContext, { value: 12345 });
+    expect(ldClient.track).toHaveBeenCalledWith(
+      'test-event',
+      translateContext(logger, basicContext),
+      undefined,
+      12345,
+    );
+  });
+
+  it('handles tracking with data but no metricValue', () => {
+    ldClient.track = jest.fn();
+    ofClient.track('test-event', basicContext, { key1: 'val1' });
+    expect(ldClient.track).toHaveBeenCalledWith(
+      'test-event',
+      translateContext(logger, basicContext),
+      { key1: 'val1' },
+      undefined,
+    );
+  });
+
+  it('handles tracking with data and metricValue', () => {
+    ldClient.track = jest.fn();
+    ofClient.track('test-event', basicContext, { value: 12345, key1: 'val1' });
+    expect(ldClient.track).toHaveBeenCalledWith(
+      'test-event',
+      translateContext(logger, basicContext),
+      { key1: 'val1' },
+      12345,
+    );
+  });
 });

__tests__/translateTrackingEventDetails.test.ts

@@ -0,0 +1,20 @@
+import translateTrackingEventDetails from '../src/translateTrackingEventDetails';
+
+it('returns undefined if details are empty', () => {
+  expect(translateTrackingEventDetails({})).toBeUndefined();
+});
+
+it('returns undefined if details only contains value', () => {
+  expect(translateTrackingEventDetails({ value: 12345 })).toBeUndefined();
+});
+
+it('returns an object without the value attribute', () => {
+  expect(translateTrackingEventDetails({
+    value: 12345,
+    key1: 'val1',
+    key2: 'val2',
+  })).toEqual({
+    key1: 'val1',
+    key2: 'val2',
+  });
+});

package.json

@@ -30,11 +30,11 @@
   "license": "Apache-2.0",
   "peerDependencies": {
     "@launchdarkly/node-server-sdk": "9.x",
-    "@openfeature/server-sdk": "^1.14.0"
+    "@openfeature/server-sdk": "^1.16.0"
   },
   "devDependencies": {
     "@launchdarkly/node-server-sdk": "9.x",
-    "@openfeature/server-sdk": "^1.14.0",
+    "@openfeature/server-sdk": "^1.16.0",
     "@types/jest": "^29.5.14",
     "@typescript-eslint/eslint-plugin": "^5.22.0",
     "@typescript-eslint/parser": "^5.22.0",

src/LaunchDarklyProvider.ts

@@ -9,12 +9,14 @@ import {
   ProviderMetadata,
   ResolutionDetails,
   StandardResolutionReasons,
+  TrackingEventDetails,
 } from '@openfeature/server-sdk';
 import {
   basicLogger, init, LDClient, LDLogger, LDOptions,
 } from '@launchdarkly/node-server-sdk';
 import translateContext from './translateContext';
 import translateResult from './translateResult';
+import translateTrackingEventDetails from './translateTrackingEventDetails';
 import SafeLogger from './SafeLogger';
 
 /**
@@ -229,4 +231,24 @@ export default class LaunchDarklyProvider implements Provider {
     await this.client.flush();
     this.client.close();
   }
+
+  /**
+   * Track a user action or application state, usually representing a business objective or outcome.
+   * @param trackingEventName The name of the event, which may correspond to a metric
+   *   in Experimentation.
+   * @param context The context to track.
+   * @param trackingEventDetails Optional additional information to associate with the event.
+   */
+  track(
+    trackingEventName: string,
+    context: EvaluationContext,
+    trackingEventDetails: TrackingEventDetails,
+  ): void {
+    this.client.track(
+      trackingEventName,
+      this.translateContext(context),
+      translateTrackingEventDetails(trackingEventDetails),
+      trackingEventDetails?.value,
+    );
+  }
 }

src/translateTrackingEventDetails.ts

@@ -0,0 +1,18 @@
+import { TrackingEventDetails, TrackingEventValue } from '@openfeature/server-sdk';
+
+/**
+ * Translate {@link TrackingEventDetails} to an object suitable for use as the data
+ * parameter in LDClient.track().
+ * @param details The {@link TrackingEventDetails} to translate.
+ * @returns An object suitable use as the data parameter in LDClient.track().
+ * The value attribute will be removed and if the resulting object is empty,
+ * returns undefined.
+ *
+ * @internal
+ */
+export default function translateTrackingEventDetails(
+  details: TrackingEventDetails,
+): Record<string, TrackingEventValue> | undefined {
+  const { value, ...data } = details;
+  return Object.keys(data).length ? data : undefined;
+}