feat: add support for abort controllers to event handlers (#1151)

Signed-off-by: Michael Beemer <[email protected]>

Author: beeme1mr

packages/react/src/evaluation/use-feature-flag.ts

@@ -280,6 +280,7 @@ function attachHandlersAndResolve<T extends FlagValue>(
   const defaultedOptions = { ...DEFAULT_OPTIONS, ...useProviderOptions(), ...normalizeOptions(options) };
   const client = useOpenFeatureClient();
   const status = useOpenFeatureClientStatus();
+  const controller = new AbortController();
 
   // suspense
   if (defaultedOptions.suspendUntilReady && status === ProviderStatus.NOT_READY) {
@@ -322,28 +323,23 @@ function attachHandlersAndResolve<T extends FlagValue>(
   useEffect(() => {
     if (status === ProviderStatus.NOT_READY) {
       // update when the provider is ready
-      client.addHandler(ProviderEvents.Ready, updateEvaluationDetailsCallback);
+      client.addHandler(ProviderEvents.Ready, updateEvaluationDetailsCallback, { signal: controller.signal });
     }
 
     if (defaultedOptions.updateOnContextChanged) {
       // update when the context changes
-      client.addHandler(ProviderEvents.ContextChanged, updateEvaluationDetailsCallback);
+      client.addHandler(ProviderEvents.ContextChanged, updateEvaluationDetailsCallback, { signal: controller.signal });
     }
-    return () => {
-      // cleanup the handlers
-      client.removeHandler(ProviderEvents.Ready, updateEvaluationDetailsCallback);
-      client.removeHandler(ProviderEvents.ContextChanged, updateEvaluationDetailsCallback);
-    };
-  }, []);
 
-  useEffect(() => {
     if (defaultedOptions.updateOnConfigurationChanged) {
       // update when the provider configuration changes
-      client.addHandler(ProviderEvents.ConfigurationChanged, configurationChangeCallback);
+      client.addHandler(ProviderEvents.ConfigurationChanged, configurationChangeCallback, {
+        signal: controller.signal,
+      });
     }
     return () => {
       // cleanup the handlers
-      client.removeHandler(ProviderEvents.ConfigurationChanged, configurationChangeCallback);
+      controller.abort();
     };
   }, []);
 

packages/react/src/provider/use-open-feature-client-status.ts

@@ -10,22 +10,18 @@ import { ProviderEvents } from '@openfeature/web-sdk';
 export function useOpenFeatureClientStatus(): ProviderStatus {
   const client = useOpenFeatureClient();
   const [status, setStatus] = useState<ProviderStatus>(client.providerStatus);
+  const controller = new AbortController();
 
   useEffect(() => {
     const updateStatus = () => setStatus(client.providerStatus);
-    client.addHandler(ProviderEvents.ConfigurationChanged, updateStatus);
-    client.addHandler(ProviderEvents.ContextChanged, updateStatus);
-    client.addHandler(ProviderEvents.Error, updateStatus);
-    client.addHandler(ProviderEvents.Ready, updateStatus);
-    client.addHandler(ProviderEvents.Stale, updateStatus);
-    client.addHandler(ProviderEvents.Reconciling, updateStatus);
+    client.addHandler(ProviderEvents.ConfigurationChanged, updateStatus, { signal: controller.signal });
+    client.addHandler(ProviderEvents.ContextChanged, updateStatus, { signal: controller.signal });
+    client.addHandler(ProviderEvents.Error, updateStatus, { signal: controller.signal });
+    client.addHandler(ProviderEvents.Ready, updateStatus, { signal: controller.signal });
+    client.addHandler(ProviderEvents.Stale, updateStatus, { signal: controller.signal });
+    client.addHandler(ProviderEvents.Reconciling, updateStatus, { signal: controller.signal });
     return () => {
-      client.removeHandler(ProviderEvents.ConfigurationChanged, updateStatus);
-      client.removeHandler(ProviderEvents.ContextChanged, updateStatus);
-      client.removeHandler(ProviderEvents.Error, updateStatus);
-      client.removeHandler(ProviderEvents.Ready, updateStatus);
-      client.removeHandler(ProviderEvents.Stale, updateStatus);
-      client.removeHandler(ProviderEvents.Reconciling, updateStatus);
+      controller.abort();
     };
   }, [client]);
 

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

@@ -12,6 +12,7 @@ import type {
   OpenFeatureError,
   FlagMetadata,
   ResolutionDetails,
+  EventOptions,
 } from '@openfeature/core';
 import {
   ErrorCode,
@@ -79,7 +80,7 @@ export class OpenFeatureClient implements Client {
     return this.providerStatusAccessor();
   }
 
-  addHandler(eventType: ProviderEvents, handler: EventHandler): void {
+  addHandler(eventType: ProviderEvents, handler: EventHandler, options?: EventOptions): void {
     this.emitterAccessor().addHandler(eventType, handler);
     const shouldRunNow = statusMatchesEvent(eventType, this._providerStatus);
 
@@ -95,6 +96,12 @@ export class OpenFeatureClient implements Client {
         this._logger?.error('Error running event handler:', err);
       }
     }
+
+    if (options?.signal && typeof options.signal.addEventListener === 'function') {
+      options.signal.addEventListener('abort', () => {
+        this.removeHandler(eventType, handler);
+      });
+    }
   }
 
   removeHandler(eventType: ProviderEvents, handler: EventHandler) {

packages/server/test/events.spec.ts

@@ -449,7 +449,21 @@ describe('Events', () => {
       expect(OpenFeature.getHandlers(eventType)).toHaveLength(0);
     });
 
-    it('The API provides a function allowing the removal of event handlers', () => {
+    it('The event handler can be removed using an abort signal', () => {
+      const abortController = new AbortController();
+      const handler1 = jest.fn();
+      const handler2 = jest.fn();
+      const eventType = ProviderEvents.Stale;
+
+      OpenFeature.addHandler(eventType, handler1, { signal: abortController.signal });
+      OpenFeature.addHandler(eventType, handler2);
+      expect(OpenFeature.getHandlers(eventType)).toHaveLength(2);
+
+      abortController.abort();
+      expect(OpenFeature.getHandlers(eventType)).toHaveLength(1);
+    });
+
+    it('The API provides a function allowing the removal of event handlers from client', () => {
       const client = OpenFeature.getClient(domain);
       const handler = jest.fn();
       const eventType = ProviderEvents.Stale;
@@ -459,6 +473,21 @@ describe('Events', () => {
       client.removeHandler(eventType, handler);
       expect(client.getHandlers(eventType)).toHaveLength(0);
     });
+
+    it('The event handler on the client can be removed using an abort signal', () => {
+      const abortController = new AbortController();
+      const client = OpenFeature.getClient(domain);
+      const handler1 = jest.fn();
+      const handler2 = jest.fn();
+      const eventType = ProviderEvents.Stale;
+
+      client.addHandler(eventType, handler1, { signal: abortController.signal });
+      client.addHandler(eventType, handler2);
+      expect(client.getHandlers(eventType)).toHaveLength(2);
+
+      abortController.abort();
+      expect(client.getHandlers(eventType)).toHaveLength(1);
+    });
   });
 
   describe('Requirement 5.3.1', () => {

packages/shared/src/events/eventing.ts

@@ -66,13 +66,17 @@ export type EventDetails<
 export type EventHandler<
   T extends ServerProviderEvents | ClientProviderEvents = ServerProviderEvents | ClientProviderEvents,
 > = (eventDetails?: EventDetails<T>) => Promise<unknown> | unknown;
+export type EventOptions = {
+  signal?: AbortSignal;
+};
 
 export interface Eventing<T extends ServerProviderEvents | ClientProviderEvents> {
   /**
    * Adds a handler for the given provider event type.
    * The handlers are called in the order they have been added.
    * @param eventType The provider event type to listen to
    * @param {EventHandler} handler The handler to run on occurrence of the event type
+   * @param {EventOptions} options Optional options such as signal for aborting
    */
   addHandler(
     eventType: T extends ClientProviderEvents
@@ -83,14 +87,17 @@ export interface Eventing<T extends ServerProviderEvents | ClientProviderEvents>
         ? ClientProviderEvents.ConfigurationChanged
         : ServerProviderEvents.ConfigurationChanged
     >,
+    options?: EventOptions,
   ): void;
   addHandler(
     eventType: T extends ClientProviderEvents ? ClientNotChangeEvents : ServerNotChangeEvents,
     handler: EventHandler<T extends ClientProviderEvents ? ClientNotChangeEvents : ServerNotChangeEvents>,
+    options?: EventOptions,
   ): void;
   addHandler(
     eventType: T extends ClientProviderEvents ? ClientProviderEvents : ServerProviderEvents,
     handler: EventHandler<T extends ClientProviderEvents ? ClientProviderEvents : ServerProviderEvents>,
+    options?: EventOptions,
   ): void;
 
   /**

packages/shared/src/open-feature.ts

@@ -7,14 +7,13 @@ import type {
   EventDetails,
   EventHandler,
   Eventing,
-  GenericEventEmitter} from './events';
-import {
-  AllProviderEvents,
-  statusMatchesEvent,
+  EventOptions,
+  GenericEventEmitter,
 } from './events';
+import { AllProviderEvents, statusMatchesEvent } from './events';
 import { isDefined } from './filter';
 import type { BaseHook, EvaluationLifeCycle } from './hooks';
-import type { Logger, ManageLogger} from './logger';
+import type { Logger, ManageLogger } from './logger';
 import { DefaultLogger, SafeLogger } from './logger';
 import type { ClientProviderStatus, CommonProvider, ProviderMetadata, ServerProviderStatus } from './provider';
 import { objectOrUndefined, stringOrUndefined } from './type-guards';
@@ -154,8 +153,9 @@ export abstract class OpenFeatureCommonAPI<
    * API (global) events run for all providers.
    * @param {AnyProviderEvent} eventType The provider event type to listen to
    * @param {EventHandler} handler The handler to run on occurrence of the event type
+   * @param {EventOptions} options Optional options such as signal for aborting
    */
-  addHandler<T extends AnyProviderEvent>(eventType: T, handler: EventHandler): void {
+  addHandler<T extends AnyProviderEvent>(eventType: T, handler: EventHandler, options?: EventOptions): void {
     [...new Map([[undefined, this._defaultProvider]]), ...this._domainScopedProviders].forEach((keyProviderTuple) => {
       const domain = keyProviderTuple[0];
       const provider = keyProviderTuple[1].provider;
@@ -173,6 +173,11 @@ export abstract class OpenFeatureCommonAPI<
     });
 
     this._apiEmitter.addHandler(eventType, handler);
+    if (options?.signal && typeof options.signal.addEventListener === 'function') {
+      options.signal.addEventListener('abort', () => {
+        this.removeHandler(eventType, handler);
+      });
+    }
   }
 
   /**
@@ -248,7 +253,7 @@ export abstract class OpenFeatureCommonAPI<
     // initialize the provider if it implements "initialize" and it's not already registered
     if (typeof provider.initialize === 'function' && !this.allProviders.includes(provider)) {
       initializationPromise = provider
-        .initialize?.(domain ? this._domainScopedContext.get(domain) ?? this._context : this._context)
+        .initialize?.(domain ? (this._domainScopedContext.get(domain) ?? this._context) : this._context)
         ?.then(() => {
           wrappedProvider.status = this._statusEnumType.READY;
           // fetch the most recent event emitters, some may have been added during init

packages/shared/test/events.spec.ts

@@ -14,17 +14,23 @@ class TestEventEmitter extends GenericEventEmitter<AnyProviderEvent> {
   }
 }
 
-// a little function to make sure we're at least waiting for the event loop 
+// a little function to make sure we're at least waiting for the event loop
 // to clear before we start making assertions
 const wait = (millis = 0) => {
-  return new Promise(resolve => {setTimeout(resolve, millis);});
+  return new Promise((resolve) => {
+    setTimeout(resolve, millis);
+  });
 };
 
 describe('GenericEventEmitter', () => {
+  const emitter = new TestEventEmitter();
+
+  afterEach(() => {
+    emitter.removeAllHandlers();
+  });
+
   describe('addHandler should', function () {
     it('attach handler for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
       emitter.emit(AllProviderEvents.Ready);
@@ -35,8 +41,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('attach several handlers for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       const handler2 = jest.fn();
       const handler3 = jest.fn();
@@ -64,7 +68,6 @@ describe('GenericEventEmitter', () => {
         debug: () => done(),
       };
 
-      const emitter = new TestEventEmitter();
       emitter.setLogger(logger);
 
       emitter.addHandler(AllProviderEvents.Ready, async () => {
@@ -74,8 +77,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('trigger handler for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
       emitter.emit(AllProviderEvents.Ready);
@@ -87,7 +88,6 @@ describe('GenericEventEmitter', () => {
 
     it('trigger handler for event type with event data', async function () {
       const event: ReadyEvent = { message: 'message' };
-      const emitter = new TestEventEmitter();
 
       const handler1 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
@@ -99,8 +99,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('trigger several handlers for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       const handler2 = jest.fn();
       const handler3 = jest.fn();
@@ -121,8 +119,6 @@ describe('GenericEventEmitter', () => {
 
   describe('removeHandler should', () => {
     it('remove single handler', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
 
@@ -138,8 +134,6 @@ describe('GenericEventEmitter', () => {
 
   describe('removeAllHandlers should', () => {
     it('remove all handlers for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       const handler2 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
@@ -156,8 +150,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('remove same handler when assigned to multiple events', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler = jest.fn();
       emitter.addHandler(AllProviderEvents.Stale, handler);
       emitter.addHandler(AllProviderEvents.ContextChanged, handler);
@@ -174,8 +166,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('allow addition/removal of duplicate handlers', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler = jest.fn();
       emitter.addHandler(AllProviderEvents.Stale, handler);
       emitter.addHandler(AllProviderEvents.Stale, handler);
@@ -191,8 +181,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('allow duplicate event handlers and call them', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler = jest.fn();
       emitter.addHandler(AllProviderEvents.Stale, handler);
       emitter.addHandler(AllProviderEvents.Stale, handler);
@@ -205,8 +193,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('remove all handlers only for event type', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       const handler2 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);
@@ -223,8 +209,6 @@ describe('GenericEventEmitter', () => {
     });
 
     it('remove all handlers if no event type is given', async function () {
-      const emitter = new TestEventEmitter();
-
       const handler1 = jest.fn();
       const handler2 = jest.fn();
       emitter.addHandler(AllProviderEvents.Ready, handler1);

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

@@ -12,6 +12,7 @@ import type {
   OpenFeatureError,
   FlagMetadata,
   ResolutionDetails,
+  EventOptions,
 } from '@openfeature/core';
 import {
   ErrorCode,
@@ -74,7 +75,7 @@ export class OpenFeatureClient implements Client {
     return this.providerStatusAccessor();
   }
 
-  addHandler(eventType: ProviderEvents, handler: EventHandler): void {
+  addHandler(eventType: ProviderEvents, handler: EventHandler, options: EventOptions): void {
     this.emitterAccessor().addHandler(eventType, handler);
     const shouldRunNow = statusMatchesEvent(eventType, this.providerStatus);
 
@@ -90,6 +91,12 @@ export class OpenFeatureClient implements Client {
         this._logger?.error('Error running event handler:', err);
       }
     }
+
+    if (options?.signal && typeof options.signal.addEventListener === 'function') {
+      options.signal.addEventListener('abort', () => {
+        this.removeHandler(eventType, handler);
+      });
+    }
   }
 
   removeHandler(notificationType: ProviderEvents, handler: EventHandler): void {