feat(core): pass bound domain to provider initialize and enforce domain-scoped binding

packages/server/src/provider/multi-provider/multi-provider.ts

@@ -104,9 +104,9 @@ export class MultiProvider implements Provider {
     Object.freeze(this.providerEntriesByName);
   }
 
-  async initialize(context?: EvaluationContext): Promise<void> {
+  async initialize(context?: EvaluationContext, domain?: string): Promise<void> {
     const result = await Promise.allSettled(
-      this.providerEntries.map((provider) => provider.provider.initialize?.(context)),
+      this.providerEntries.map((provider) => provider.provider.initialize?.(context, domain)),
     );
     throwAggregateErrorFromPromiseResults(result, this.providerEntries);
   }

packages/server/test/multi-provider.spec.ts

@@ -22,6 +22,7 @@ import {
   FirstSuccessfulStrategy,
   ComparisonStrategy,
 } from '../src';
+import { legacyInitializeProvider } from '../../shared/test/legacy-initialize-provider';
 
 class TestProvider implements Provider {
   public metadata: ProviderMetadata = {
@@ -162,6 +163,39 @@ describe('MultiProvider', () => {
       expect(initializations).toBe(2);
     });
 
+    it('forwards domain to legacy single-argument child providers without error', async () => {
+      const legacyProvider1 = legacyInitializeProvider(
+        { runsOn: 'server', asyncResolvers: true, name: 'LegacyInitTestProvider' },
+        { events: new OpenFeatureEventEmitter() },
+      );
+      const legacyProvider2 = legacyInitializeProvider(
+        { runsOn: 'server', asyncResolvers: true, name: 'LegacyInitTestProvider' },
+        { events: new OpenFeatureEventEmitter() },
+      );
+      const multiProvider = new MultiProvider([
+        { provider: legacyProvider1 as unknown as Provider },
+        { provider: legacyProvider2 as unknown as Provider },
+      ]);
+
+      await multiProvider.initialize({ targetingKey: 'user' }, 'my-domain');
+
+      expect(legacyProvider1.initializeCalls).toBe(1);
+      expect(legacyProvider2.initializeCalls).toBe(1);
+      expect(legacyProvider1.lastContext).toEqual({ targetingKey: 'user' });
+      expect(legacyProvider2.lastContext).toEqual({ targetingKey: 'user' });
+    });
+
+    it('forwards domain to child provider initialize', async () => {
+      const provider1 = new TestProvider();
+      const provider2 = new TestProvider();
+      const multiProvider = new MultiProvider([{ provider: provider1 }, { provider: provider2 }]);
+
+      await multiProvider.initialize({ targetingKey: 'user' }, 'my-domain');
+
+      expect(provider1.initialize).toHaveBeenCalledWith({ targetingKey: 'user' }, 'my-domain');
+      expect(provider2.initialize).toHaveBeenCalledWith({ targetingKey: 'user' }, 'my-domain');
+    });
+
     it('throws error if a provider errors on initialization', async () => {
       const provider1 = new TestProvider();
       const provider2 = new TestProvider();

packages/server/test/open-feature.spec.ts

@@ -1,7 +1,8 @@
 import type { Paradigm } from '@openfeature/core';
-import type { Provider, ProviderStatus } from '../src';
-import { OpenFeature, OpenFeatureAPI } from '../src';
+import type { Provider } from '../src';
+import { OpenFeature, OpenFeatureAPI, ProviderStatus } from '../src';
 import { OpenFeatureClient } from '../src/client/internal/open-feature-client';
+import { legacyInitializeProvider } from '../../shared/test/legacy-initialize-provider';
 
 const mockProvider = (config?: { initialStatus?: ProviderStatus; runsOn?: Paradigm }) => {
   return {
@@ -57,6 +58,41 @@
         expect(OpenFeature.providerMetadata.name).toBe('mock-events-success');
         expect(provider.initialize).toHaveBeenCalled();
       });
+
+      it('MUST supply the bound domain to initialize when registering a domain-scoped provider', () => {
+        const domain = 'my-domain';
+        const provider = { ...mockProvider(), domainScoped: true } as Provider;
+        const spy = jest.spyOn(provider, 'initialize');
+        OpenFeature.setProvider(domain, provider);
+        expect(spy).toHaveBeenCalledWith({}, domain);
+      });
+
+      it('MUST not supply a domain to initialize for the default provider', () => {
+        const provider = mockProvider();
+        const spy = jest.spyOn(provider, 'initialize');
+        OpenFeature.setProvider(provider);
+        expect(spy).toHaveBeenCalledWith({}, undefined);
+      });
+
+      it('initializes legacy single-argument providers when bound to a domain', async () => {
+        const domain = 'my-domain';
+        const context = { targetingKey: 'user' };
+        const legacyProvider = legacyInitializeProvider({ runsOn: 'server', asyncResolvers: true });
+        OpenFeature.setContext(context);
+
+        await expect(
+          OpenFeature.setProviderAndWait(domain, legacyProvider as unknown as Provider),
+        ).resolves.toBeUndefined();
+        expect(legacyProvider.lastContext).toEqual(context);
+        expect(OpenFeature.getClient(domain).providerStatus).toEqual(ProviderStatus.READY);
+      });
+
+      it('initializes legacy single-argument providers as the default provider', async () => {
+        const legacyProvider = legacyInitializeProvider({ runsOn: 'server', asyncResolvers: true });
+
+        await expect(OpenFeature.setProviderAndWait(legacyProvider as unknown as Provider)).resolves.toBeUndefined();
+        expect(OpenFeature.getClient().providerStatus).toEqual(ProviderStatus.READY);
+      });
     });
 
     describe('Requirement 1.1.2.3', () => {
@@ -68,6 +104,51 @@
         expect(provider.onClose).toHaveBeenCalled();
       });
     });
+
+    describe('Condition 1.1.8', () => {
+      it('MUST NOT bind a domain-scoped provider instance to more than one domain', () => {
+        const provider = { ...mockProvider(), domainScoped: true } as Provider;
+
+        OpenFeature.setProvider('domain-a', provider);
+        expect(() => OpenFeature.setProvider('domain-b', provider)).toThrow(
+          "Cannot bind domain-scoped provider 'mock-events-success' to more than one domain.",
+        );
+        expect(OpenFeature.getProvider('domain-a')).toBe(provider);
+        expect(OpenFeature.getProvider('domain-b').metadata.name).not.toBe(provider.metadata.name);
+      });
+
+      it('MUST NOT bind a domain-scoped default provider to a named domain', () => {
+        const provider = { ...mockProvider(), domainScoped: true } as Provider;
+
+        OpenFeature.setProvider(provider);
+        expect(() => OpenFeature.setProvider('domain-a', provider)).toThrow(
+          "Cannot bind domain-scoped provider 'mock-events-success' to more than one domain.",
+        );
+        expect(OpenFeature.getProvider()).toBe(provider);
+        expect(OpenFeature.getProvider('domain-a').metadata.name).not.toBe(provider.metadata.name);
+      });
+
+      it('MUST NOT bind a domain-scoped provider as default when already bound to a domain', () => {
+        const provider = { ...mockProvider(), domainScoped: true } as Provider;
+
+        OpenFeature.setProvider('domain-a', provider);
+        expect(() => OpenFeature.setProvider(provider)).toThrow(
+          "Cannot bind domain-scoped provider 'mock-events-success' to more than one domain.",
+        );
+        expect(OpenFeature.getProvider('domain-a')).toBe(provider);
+      });
+
+      it('allows a non-domain-scoped provider to back multiple domains', async () => {
+        const provider = { ...mockProvider(), onClose: jest.fn() };
+
+        await OpenFeature.setProviderAndWait('domain1', provider);
+        await OpenFeature.setProviderAndWait('domain2', provider);
+
+        expect(OpenFeature.getProvider('domain1')).toBe(provider);
+        expect(OpenFeature.getProvider('domain2')).toBe(provider);
+        expect(provider.initialize).toHaveBeenCalledTimes(1);
+      });
+    });
   });
 
   describe('Requirement 1.1.3', () => {

packages/shared/src/open-feature.ts

@@ -231,6 +231,12 @@ export abstract class OpenFeatureCommonAPI<
 
     // ignore no-ops
     if (oldProvider === provider) {
+      // domain-scoped providers may already be the default; an explicit domain bind is not a no-op
+      if (provider.domainScoped && domain && this._domainScopedProviders.get(domain)?.provider !== provider) {
+        throw new GeneralError(
+          `Cannot bind domain-scoped provider '${provider.metadata.name}' to more than one domain.`,
+        );
+      }
       this._logger.debug('Provider is already set, ignoring setProvider call');
       return;
     }
@@ -241,6 +247,10 @@ export abstract class OpenFeatureCommonAPI<
       throw new GeneralError(`Provider '${provider.metadata.name}' is intended for use on the ${provider.runsOn}.`);
     }
 
+    if (provider.domainScoped && this.allProviders.includes(provider)) {
+      throw new GeneralError(`Cannot bind domain-scoped provider '${provider.metadata.name}' to more than one domain.`);
+    }
+
     const emitters = this.getAssociatedEventEmitters(domain);
 
     let initializationPromise: Promise<void> | void = undefined;
@@ -252,8 +262,9 @@ 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)) {
+      const initContext = domain ? (this._domainScopedContext.get(domain) ?? this._context) : this._context;
       initializationPromise = provider
-        .initialize?.(domain ? (this._domainScopedContext.get(domain) ?? this._context) : this._context)
+        .initialize?.(initContext, domain)
         ?.then(() => {
           wrappedProvider.status = this._statusEnumType.READY;
           // fetch the most recent event emitters, some may have been added during init

packages/shared/src/provider/provider.ts

@@ -96,6 +96,12 @@ export interface CommonProvider<S extends ClientProviderStatus | ServerProviderS
    */
   readonly runsOn?: Paradigm;
 
+  /**
+   * When true, the provider maintains state specific to a single domain (such as a
+   * persistent cache) and the SDK will bind it to at most one domain.
+   */
+  readonly domainScoped?: boolean;
+
   // TODO: in the future we could make this a never to force provider to remove it.
   /**
    * @deprecated the SDK now maintains the provider's state; there's no need for providers to implement this field.
@@ -123,9 +129,10 @@ export interface CommonProvider<S extends ClientProviderStatus | ServerProviderS
    * When the returned promise resolves, the SDK fires the ProviderEvents.Ready event.
    * If the returned promise rejects, the SDK fires the ProviderEvents.Error event.
    * Use this function to perform any context-dependent setup within the provider.
-   * @param context
+   * @param context the global evaluation context
+   * @param domain the bound domain, if any
    */
-  initialize?(context?: EvaluationContext): Promise<void>;
+  initialize?(context?: EvaluationContext, domain?: string): Promise<void>;
 
   /**
    * Track a user action or application state, usually representing a business objective or outcome.

packages/shared/test/legacy-initialize-provider.ts

@@ -0,0 +1,73 @@
+import type { EvaluationContext, Paradigm } from '../src';
+
+type LegacyInitializeProviderOptions = {
+  runsOn: Paradigm;
+  name?: string;
+  /** When true, resolution stubs return promises (server SDK). Default false (web SDK). */
+  asyncResolvers?: boolean;
+};
+
+type LegacyInitializeProviderExtras = {
+  events: unknown;
+  hooks?: unknown[];
+  track?: jest.Mock;
+};
+
+type LegacyInitializeProviderResolvers = {
+  resolveBooleanEvaluation: jest.Mock;
+  resolveStringEvaluation: jest.Mock;
+  resolveNumberEvaluation: jest.Mock;
+  resolveObjectEvaluation: jest.Mock;
+};
+
+export type LegacyInitializeProvider = LegacyInitializeProviderResolvers & {
+  metadata: { name: string };
+  runsOn: Paradigm;
+  lastContext?: EvaluationContext;
+  initializeCalls: number;
+  initialize: (context?: EvaluationContext) => Promise<void>;
+};
+
+function createResolverStubs(asyncResolvers: boolean): LegacyInitializeProviderResolvers {
+  const mockValue = asyncResolvers
+    ? <T>(value: T) => jest.fn().mockResolvedValue(value)
+    : <T>(value: T) => jest.fn().mockReturnValue(value);
+
+  return {
+    resolveBooleanEvaluation: mockValue({ value: false }),
+    resolveStringEvaluation: mockValue({ value: '' }),
+    resolveNumberEvaluation: mockValue({ value: 0 }),
+    resolveObjectEvaluation: mockValue({ value: {} }),
+  };
+}
+
+/**
+ * Provider with a single-argument initialize that ignores any extra arguments passed by the SDK.
+ * Pass optional extras when MultiProvider needs events, hooks, or track stubs on the child.
+ */
+export function legacyInitializeProvider(
+  options: LegacyInitializeProviderOptions,
+  extras?: LegacyInitializeProviderExtras,
+): LegacyInitializeProvider {
+  const provider: LegacyInitializeProvider = {
+    metadata: { name: options.name ?? 'legacy-init' },
+    runsOn: options.runsOn,
+    lastContext: undefined,
+    initializeCalls: 0,
+    async initialize(context?: EvaluationContext): Promise<void> {
+      this.lastContext = context;
+      this.initializeCalls++;
+    },
+    ...createResolverStubs(options.asyncResolvers ?? false),
+  };
+
+  if (extras) {
+    Object.assign(provider, {
+      events: extras.events,
+      hooks: extras.hooks ?? [],
+      track: extras.track ?? jest.fn(),
+    });
+  }
+
+  return provider;
+}

packages/web/src/provider/multi-provider/multi-provider-web.ts

@@ -103,9 +103,9 @@ export class MultiProvider implements Provider {
     Object.freeze(this.providerEntriesByName);
   }
 
-  async initialize(context?: EvaluationContext): Promise<void> {
+  async initialize(context?: EvaluationContext, domain?: string): Promise<void> {
     const result = await Promise.allSettled(
-      this.providerEntries.map((provider) => provider.provider.initialize?.(context)),
+      this.providerEntries.map((provider) => provider.provider.initialize?.(context, domain)),
     );
     throwAggregateErrorFromPromiseResults(result, this.providerEntries);
   }

packages/web/test/evaluation-context.spec.ts

@@ -84,7 +84,7 @@ describe('Evaluation Context', () => {
         const context: EvaluationContext = { property1: false };
         const provider = new MockProvider();
         await OpenFeature.setProviderAndWait(provider, context);
-        expect(initializeMock).toHaveBeenCalledWith(context);
+        expect(initializeMock).toHaveBeenCalledWith(context, undefined);
         expect(OpenFeature.getContext()).toEqual(context);
       });
 
@@ -95,7 +95,7 @@ describe('Evaluation Context', () => {
         await OpenFeature.setProviderAndWait(domain, provider, context);
         expect(OpenFeature.getContext()).toEqual({});
         expect(OpenFeature.getContext(domain)).toEqual(context);
-        expect(initializeMock).toHaveBeenCalledWith(context);
+        expect(initializeMock).toHaveBeenCalledWith(context, domain);
       });
     });
 

packages/web/test/multi-provider-web.spec.ts

@@ -23,6 +23,7 @@ import {
   FirstSuccessfulStrategy,
   ComparisonStrategy,
 } from '../src';
+import { legacyInitializeProvider } from '../../shared/test/legacy-initialize-provider';
 
 class TestProvider implements Provider {
   public metadata: ProviderMetadata = {
@@ -162,6 +163,39 @@ describe('MultiProvider', () => {
       expect(initializations).toBe(2);
     });
 
+    it('forwards domain to legacy single-argument child providers without error', async () => {
+      const legacyProvider1 = legacyInitializeProvider(
+        { runsOn: 'client', name: 'LegacyInitTestProvider' },
+        { events: new OpenFeatureEventEmitter() },
+      );
+      const legacyProvider2 = legacyInitializeProvider(
+        { runsOn: 'client', name: 'LegacyInitTestProvider' },
+        { events: new OpenFeatureEventEmitter() },
+      );
+      const multiProvider = new MultiProvider([
+        { provider: legacyProvider1 as unknown as Provider },
+        { provider: legacyProvider2 as unknown as Provider },
+      ]);
+
+      await multiProvider.initialize({ targetingKey: 'user' }, 'my-domain');
+
+      expect(legacyProvider1.initializeCalls).toBe(1);
+      expect(legacyProvider2.initializeCalls).toBe(1);
+      expect(legacyProvider1.lastContext).toEqual({ targetingKey: 'user' });
+      expect(legacyProvider2.lastContext).toEqual({ targetingKey: 'user' });
+    });
+
+    it('forwards domain to child provider initialize', async () => {
+      const provider1 = new TestProvider();
+      const provider2 = new TestProvider();
+      const multiProvider = new MultiProvider([{ provider: provider1 }, { provider: provider2 }]);
+
+      await multiProvider.initialize({ targetingKey: 'user' }, 'my-domain');
+
+      expect(provider1.initialize).toHaveBeenCalledWith({ targetingKey: 'user' }, 'my-domain');
+      expect(provider2.initialize).toHaveBeenCalledWith({ targetingKey: 'user' }, 'my-domain');
+    });
+
     it('throws error if a provider errors on initialization', async () => {
       const provider1 = new TestProvider();
       const provider2 = new TestProvider();