feat: implement tracking as per spec (#1020)

📣 This was a draft for a while, but is now ready for review! 📣

This implements tracking as per spec, in the server, web, and react
SDKs.
I don't think the Angular or Nest SDKs need specific implementations,
but please advise (cc @luizgribeiro @lukas-reining).

Fixes: #1033
Fixes: #1034

---------

Signed-off-by: Todd Baert <[email protected]>

packages/react/src/context/use-context-mutator.ts

@@ -15,7 +15,7 @@ export type ContextMutationOptions = {
 
 export type ContextMutation = {
   /**
-   * A function to set the desired context (see: {@link ContextMutationOptions} for details).
+   * Context-aware function to set the desired context (see: {@link ContextMutationOptions} for details).
    * There's generally no need to await the result of this function; flag evaluation hooks will re-render when the context is updated.
    * This promise never rejects.
    * @param updatedContext
@@ -25,10 +25,10 @@ export type ContextMutation = {
 };
 
 /**
- * Get function(s) for mutating the evaluation context associated with this domain, or the default context if `defaultContext: true`.
+ * Get context-aware tracking function(s) for mutating the evaluation context associated with this domain, or the default context if `defaultContext: true`.
  * See the {@link https://openfeature.dev/docs/reference/technologies/client/web/#targeting-and-context|documentation} for more information.
  * @param {ContextMutationOptions} options options for the generated function
- * @returns {ContextMutation} function(s) to mutate context
+ * @returns {ContextMutation} context-aware function(s) to mutate evaluation context
  */
 export function useContextMutator(options: ContextMutationOptions = { defaultContext: false }): ContextMutation {
     const { domain } = useContext(Context) || {};

packages/react/src/index.ts

@@ -2,5 +2,6 @@ export * from './evaluation';
 export * from './query';
 export * from './provider';
 export * from './context';
+export * from './tracking';
 // re-export the web-sdk so consumers can access that API from the react-sdk
 export * from '@openfeature/web-sdk';

packages/react/src/tracking/index.ts

@@ -0,0 +1 @@
+export * from './use-track';

packages/react/src/tracking/use-track.ts

@@ -0,0 +1,29 @@
+import type { Tracking, TrackingEventDetails } from '@openfeature/web-sdk';
+import { useCallback } from 'react';
+import { useOpenFeatureClient } from '../provider';
+
+export type Track = {
+  /**
+   * Context-aware tracking function for the parent `<OpenFeatureProvider/>`.
+   * Track a user action or application state, usually representing a business objective or outcome.
+   * @param trackingEventName an identifier for the event
+   * @param trackingEventDetails the details of the tracking event
+   */
+  track: Tracking['track'];
+};
+
+/**
+ * Get a context-aware tracking function.
+ * @returns {Track} context-aware tracking
+ */
+export function useTrack(): Track {
+  const client = useOpenFeatureClient();
+
+  const track = useCallback((trackingEventName: string, trackingEventDetails?: TrackingEventDetails) => {
+    client.track(trackingEventName, trackingEventDetails);
+  }, []);
+
+  return {
+    track,
+  };
+}

packages/react/test/tracking.spec.tsx

@@ -0,0 +1,88 @@
+import { jest } from '@jest/globals';
+import '@testing-library/jest-dom'; // see: https://testing-library.com/docs/react-testing-library/setup
+import { render } from '@testing-library/react';
+import * as React from 'react';
+import type { Provider, TrackingEventDetails } from '../src';
+import {
+  OpenFeature,
+  OpenFeatureProvider,
+  useTrack
+} from '../src';
+
+describe('tracking', () => {
+
+  const eventName = 'test-tracking-event';
+  const trackingValue = 1234;
+  const trackingDetails: TrackingEventDetails = {
+    value: trackingValue,
+  };
+  const domain = 'someDomain';
+
+  const mockProvider = () => {
+    const mockProvider: Provider = {
+      metadata: {
+        name: 'mock',
+      },
+
+      track: jest.fn((): void => {
+        return;
+      }),
+    } as unknown as Provider;
+
+    return mockProvider;
+  };
+
+  describe('no domain', () => {
+    it('should call default provider', async () => {
+
+      const provider = mockProvider();
+      await OpenFeature.setProviderAndWait(provider);
+
+      function Component() {
+        const { track } = useTrack();
+        track(eventName, trackingDetails);
+
+        return <div></div>;
+      }
+
+      render(
+        <OpenFeatureProvider suspend={false} >
+            <Component></Component>
+        </OpenFeatureProvider>,
+      );
+
+      expect(provider.track).toHaveBeenCalledWith(
+        eventName,
+        expect.anything(),
+        expect.objectContaining({ value: trackingValue }),
+      );
+    });
+  });
+
+  describe('domain set', () => {
+    it('should call provider for domain', async () => {
+
+      const domainProvider = mockProvider();
+      await OpenFeature.setProviderAndWait(domain, domainProvider);
+
+      function Component() {
+        const { track } = useTrack();
+        track(eventName, trackingDetails);
+
+        return <div></div>;
+      }
+
+      render(
+        <OpenFeatureProvider domain={domain} suspend={false} >
+            <Component></Component>
+        </OpenFeatureProvider>,
+      );
+
+      expect(domainProvider.track).toHaveBeenCalledWith(
+        eventName,
+        expect.anything(),
+        expect.objectContaining({ value: trackingValue }),
+      );
+    });
+  });
+});

packages/server/src/client/client.ts

@@ -8,12 +8,14 @@ import type {
 import type { Features } from '../evaluation';
 import type { ProviderStatus } from '../provider';
 import type { ProviderEvents } from '../events';
+import type { Tracking } from '../tracking';
 
 export interface Client
   extends EvaluationLifeCycle<Client>,
     Features,
     ManageContext<Client>,
     ManageLogger<Client>,
+    Tracking,
     Eventing<ProviderEvents> {
   readonly metadata: ClientMetadata;
   /**

packages/server/src/client/internal/open-feature-client.ts

@@ -8,6 +8,7 @@ import type {
   HookContext,
   JsonValue,
   Logger,
+  TrackingEventDetails,
   OpenFeatureError,
   ResolutionDetails} from '@openfeature/core';
 import {
@@ -23,7 +24,6 @@ import type { FlagEvaluationOptions } from '../../evaluation';
 import type { ProviderEvents } from '../../events';
 import type { InternalEventEmitter } from '../../events/internal/internal-event-emitter';
 import type { Hook } from '../../hooks';
-import { OpenFeature } from '../../open-feature';
 import type { Provider} from '../../provider';
 import { ProviderStatus } from '../../provider';
 import type { Client } from './../client';
@@ -53,6 +53,9 @@ export class OpenFeatureClient implements Client {
     private readonly providerAccessor: () => Provider,
     private readonly providerStatusAccessor: () => ProviderStatus,
     private readonly emitterAccessor: () => InternalEventEmitter,
+    private readonly apiContextAccessor: () => EvaluationContext,
+    private readonly apiHooksAccessor: () => Hook[],
+    private readonly transactionContextAccessor: () => EvaluationContext,
     private readonly globalLogger: () => Logger,
     private readonly options: OpenFeatureClientOptions,
     context: EvaluationContext = {},
@@ -223,6 +226,22 @@ export class OpenFeatureClient implements Client {
     return this.evaluate<T>(flagKey, this._provider.resolveObjectEvaluation, defaultValue, 'object', context, options);
   }
 
+  track(occurrenceKey: string, context: EvaluationContext, occurrenceDetails: TrackingEventDetails): void {
+    try {
+      this.shortCircuitIfNotReady();
+
+      if (typeof this._provider.track === 'function') {
+        // freeze the merged context
+        const frozenContext = Object.freeze(this.mergeContexts(context));
+        return this._provider.track?.(occurrenceKey, frozenContext, occurrenceDetails);
+      } else {
+        this._logger.debug('Provider does not support the track function; will no-op.');
+      }
+    } catch (err) {
+      this._logger.debug('Error recording tracking event.', err);
+    }
+  }
+
   private async evaluate<T extends FlagValue>(
     flagKey: string,
     resolver: (
@@ -239,20 +258,14 @@ export class OpenFeatureClient implements Client {
     // merge global, client, and evaluation context
 
     const allHooks = [
-      ...OpenFeature.getHooks(),
+      ...this.apiHooksAccessor(),
       ...this.getHooks(),
       ...(options.hooks || []),
       ...(this._provider.hooks || []),
     ];
     const allHooksReversed = [...allHooks].reverse();
 
-    // merge global and client contexts
-    const mergedContext = {
-      ...OpenFeature.getContext(),
-      ...OpenFeature.getTransactionContext(),
-      ...this._context,
-      ...invocationContext,
-    };
+    const mergedContext = this.mergeContexts(invocationContext);
 
     // this reference cannot change during the course of evaluation
     // it may be used as a key in WeakMaps
@@ -269,12 +282,7 @@ export class OpenFeatureClient implements Client {
     try {
       const frozenContext = await this.beforeHooks(allHooks, hookContext, options);
 
-      // short circuit evaluation entirely if provider is in a bad state
-      if (this.providerStatus === ProviderStatus.NOT_READY) {
-        throw new ProviderNotReadyError('provider has not yet initialized');
-      } else if (this.providerStatus === ProviderStatus.FATAL) {
-        throw new ProviderFatalError('provider is in an irrecoverable error state');
-      }
+      this.shortCircuitIfNotReady();
 
       // run the referenced resolver, binding the provider.
       const resolution = await resolver.call(this._provider, flagKey, defaultValue, frozenContext, this._logger);
@@ -380,4 +388,23 @@ export class OpenFeatureClient implements Client {
   private get _logger() {
     return this._clientLogger || this.globalLogger();
   }
+
+  private mergeContexts(invocationContext: EvaluationContext) {
+    // merge global and client contexts
+    return {
+      ...this.apiContextAccessor(),
+      ...this.transactionContextAccessor(),
+      ...this._context,
+      ...invocationContext,
+    };
+  }
+
+  private shortCircuitIfNotReady() {
+    // short circuit evaluation entirely if provider is in a bad state
+    if (this.providerStatus === ProviderStatus.NOT_READY) {
+      throw new ProviderNotReadyError('provider has not yet initialized');
+    } else if (this.providerStatus === ProviderStatus.FATAL) {
+      throw new ProviderFatalError('provider is in an irrecoverable error state');
+    }
+  }
 }

packages/server/src/index.ts

@@ -5,4 +5,5 @@ export * from './open-feature';
 export * from './transaction-context';
 export * from './events';
 export * from './hooks';
+export * from './tracking';
 export * from '@openfeature/core';

packages/server/src/open-feature.ts

@@ -198,6 +198,9 @@ export class OpenFeatureAPI
       () => this.getProviderForClient(domain),
       () => this.getProviderStatus(domain),
       () => this.buildAndCacheEventEmitterForClient(domain),
+      () => this.getContext(),
+      () => this.getHooks(),
+      () => this.getTransactionContext(),
       () => this._logger,
       { domain, version },
       context,

packages/server/src/provider/provider.ts

@@ -1,5 +1,12 @@
-import type { CommonProvider, EvaluationContext, JsonValue, Logger, ResolutionDetails} from '@openfeature/core';
-import { ServerProviderStatus } from '@openfeature/core';
+import type {
+  CommonProvider,
+  EvaluationContext,
+  JsonValue,
+  Logger,
+  ResolutionDetails} from '@openfeature/core';
+import {
+  ServerProviderStatus,
+} from '@openfeature/core';
 import type { Hook } from '../hooks';
 
 export { ServerProviderStatus as ProviderStatus };

packages/server/src/tracking/index.ts

@@ -0,0 +1 @@
+export * from './tracking';

packages/server/src/tracking/tracking.ts

@@ -0,0 +1,12 @@
+import type { EvaluationContext, TrackingEventDetails } from '@openfeature/core';
+
+export interface Tracking {
+
+  /**
+   * Track a user action or application state, usually representing a business objective or outcome.
+   * @param trackingEventName an identifier for the event
+   * @param context the evaluation context
+   * @param trackingEventDetails the details of the tracking event
+   */
+  track(trackingEventName: string, context?: EvaluationContext, trackingEventDetails?: TrackingEventDetails): void;
+}