feat: allow a handler to subscribe to multiple events (#179)

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##### Checklist
<!-- Remove items that do not apply. For completed items, change [ ] to
[x]. -->

- [x] `npm test` passes
- [x] tests and/or benchmarks are included
- [x] documentation is changed or added
- [x] commit message follows commit guidelines

##### Affected core subsystem(s)
<!-- Provide affected core subsystem(s). -->
`plugin/eventbus`  `eventbus-decorator`  `eventbus-runtime` 

##### Description of change
<!-- Provide a description of the change below this comment. -->
allow a handler to subscribe to multiple events
<!--
- any feature?
- close https://github.com/eggjs/egg/ISSUE_URL
-->

core/eventbus-decorator/README.md

@@ -56,3 +56,29 @@ export class Foo {
   }
 }
 ```
+
+### handle multiple event
+```ts
+@Event('hello')
+@Event('hi')
+export class Foo {
+  async handle(msg: string): Promise<void> {
+    console.log('msg: ', msg);
+  }
+}
+```
+
+### inject event context 
+inject event context  if you want to know which event is being handled.
+The context param must be the first param
+
+```ts
+@Event('hello')
+@Event('hi')
+export class Foo {
+  async handle(@EventContext() ctx: IEventContext, msg: string):Promise<void> {
+    console.log('eventName: ', ctx.eventName);
+    console.log('msg: ', msg);
+  }
+}
+```

core/eventbus-decorator/index.ts

@@ -1,6 +1,7 @@
 export * from './src/EventBus';
 export * from './src/Event';
 export * from './src/EventInfoUtil';
+export * from './src/EventContext';
 
 // trick for use declaration
 export interface Events {

core/eventbus-decorator/src/Event.ts

@@ -4,11 +4,11 @@ import { EventHandler } from '../index';
 import { EventInfoUtil } from './EventInfoUtil';
 // use @eggjs/tegg as namespace
 // eslint-disable-next-line import/no-unresolved
-import { Events } from '@eggjs/tegg';
+import type { Events } from '@eggjs/tegg';
 
 export function Event<E extends keyof Events>(eventName: E) {
   return function(clazz: new () => EventHandler<E>) {
-    EventInfoUtil.setEventName(eventName, clazz);
+    EventInfoUtil.addEventName(eventName, clazz);
     const func = SingletonProto({
       accessLevel: AccessLevel.PUBLIC,
     });

core/eventbus-decorator/src/EventBus.ts

@@ -1,9 +1,12 @@
-import TypedEventEmitter, { Arguments } from 'typed-emitter';
+import TypedEventEmitter from 'typed-emitter';
+import type { Arguments } from 'typed-emitter';
 // use @eggjs/tegg as namespace
 // eslint-disable-next-line import/no-unresolved
-import { Events } from '@eggjs/tegg';
+import type { Events } from '@eggjs/tegg';
+import { IEventContext } from './EventContext';
 
 export type EventName = string | symbol;
+export type { Arguments } from 'typed-emitter';
 
 /**
  * use `emit` to emit a event
@@ -38,6 +41,10 @@ export interface EventWaiter {
   awaitFirst<E1 extends EventKeys, E2 extends EventKeys, E3 extends EventKeys, E4 extends EventKeys>(e1: E1, e2: E2, e3: E3, e4: E4): Promise<{ event: E1 | E2 | E3 | E4, args: Arguments<Events[E1] | Events[E2] | Events[E3] | Events[E4]> }>
 }
 
-export interface EventHandler<E extends keyof Events> {
+type EventHandlerWithContext<E extends keyof Events> = {
+  handle: (ctx: IEventContext, ...args: Arguments<Events[E]>) => ReturnType<Events[E]>
+};
+
+export type EventHandler<E extends keyof Events> = {
   handle: Events[E];
-}
+} | EventHandlerWithContext<E>;

core/eventbus-decorator/src/EventContext.ts

@@ -0,0 +1,21 @@
+// use @eggjs/tegg as namespace
+// eslint-disable-next-line import/no-unresolved
+import type { Events } from '@eggjs/tegg';
+import { EggProtoImplClass } from '@eggjs/core-decorator';
+import assert from 'assert';
+import { EventInfoUtil } from './EventInfoUtil';
+
+export interface IEventContext{
+  eventName: keyof Events
+}
+
+export function EventContext() {
+  return function(target: any, propertyKey: PropertyKey, parameterIndex: number) {
+    assert(propertyKey === 'handle',
+      `[eventHandler ${target.name}] expect method name be handle, but now is ${String(propertyKey)}`);
+    assert(parameterIndex === 0,
+      `[eventHandler ${target.name}] expect param EventContext be the first param`);
+    const clazz = target.constructor as EggProtoImplClass;
+    EventInfoUtil.setEventHandlerContextInject(true, clazz);
+  };
+}

core/eventbus-decorator/src/EventInfoUtil.ts

@@ -2,13 +2,42 @@ import { EggProtoImplClass, MetadataUtil } from '@eggjs/core-decorator';
 import { EventName } from './EventBus';
 
 export const EVENT_NAME = Symbol.for('EggPrototype#eventName');
+export const EVENT_CONTEXT_INJECT = Symbol.for('EggPrototype#event#handler#context#inject');
 
 export class EventInfoUtil {
+  /**
+   * @deprecated
+   */
   static setEventName(eventName: EventName, clazz: EggProtoImplClass) {
-    MetadataUtil.defineMetaData(EVENT_NAME, eventName, clazz);
+    EventInfoUtil.addEventName(eventName, clazz);
   }
 
+  static addEventName(eventName: EventName, clazz: EggProtoImplClass) {
+    const eventNameList = MetadataUtil.initOwnArrayMetaData<EventName>(EVENT_NAME, clazz, []);
+    eventNameList.push(eventName);
+  }
+
+  static getEventNameList(clazz: EggProtoImplClass): EventName[] {
+    return MetadataUtil.getArrayMetaData(EVENT_NAME, clazz);
+  }
+
+  /**
+   * @deprecated
+   * return the last eventName which is subscribed firstly by Event decorator
+   */
   static getEventName(clazz: EggProtoImplClass): EventName | undefined {
-    return MetadataUtil.getMetaData(EVENT_NAME, clazz);
+    const eventNameList = MetadataUtil.initOwnArrayMetaData<EventName>(EVENT_NAME, clazz, []);
+    if (eventNameList.length !== 0) {
+      return eventNameList[eventNameList.length - 1];
+    }
+    return undefined;
+  }
+
+  static setEventHandlerContextInject(enable: boolean, clazz: EggProtoImplClass): void {
+    MetadataUtil.defineMetaData(EVENT_CONTEXT_INJECT, enable, clazz);
+  }
+
+  static getEventHandlerContextInject(clazz: EggProtoImplClass): boolean {
+    return MetadataUtil.getMetaData(EVENT_CONTEXT_INJECT, clazz) ?? false;
   }
 }

core/eventbus-decorator/test/Event.test.ts

@@ -2,12 +2,34 @@ import assert from 'assert';
 import path from 'path';
 import coffee from 'coffee';
 import { FooHandler } from './fixtures/right-event-handle';
+import { MultiHandler } from './fixtures/multiple-events-handle';
+import { EventContextHandler } from './fixtures/event-handle-with-context';
+import { EmptyHandler } from './fixtures/empty-handle';
 import { EventInfoUtil } from '../src/EventInfoUtil';
 
 describe('test/Event.test.ts', () => {
-  it('should work', () => {
-    const eventName = EventInfoUtil.getEventName(FooHandler);
-    assert(eventName === 'foo');
+  it('getEventName should work', () => {
+    assert.equal(EventInfoUtil.getEventName(FooHandler), 'foo');
+    assert.equal(EventInfoUtil.getEventName(EmptyHandler), undefined);
+  });
+
+  it('getEventNameList should work', function() {
+    const event = EventInfoUtil.getEventName(MultiHandler);
+    assert.deepStrictEqual(event, 'hello');
+    const eventList = EventInfoUtil.getEventNameList(MultiHandler);
+    assert.deepStrictEqual(eventList, [ 'hi', 'hello' ]);
+  });
+
+  it('setEventName should work', function() {
+    EventInfoUtil.setEventName('foo', EmptyHandler);
+    assert.equal(EventInfoUtil.getEventName(EmptyHandler), 'foo');
+    EventInfoUtil.setEventName('bar', EmptyHandler);
+    assert.equal(EventInfoUtil.getEventName(EmptyHandler), 'bar');
+  });
+
+  it('getEventHandlerContextInject', function() {
+    assert.equal(EventInfoUtil.getEventHandlerContextInject(EventContextHandler), true);
+    assert.equal(EventInfoUtil.getEventHandlerContextInject(FooHandler), false);
   });
 
   it('event type check should work', async () => {

core/eventbus-decorator/test/fixtures/empty-handle.ts

@@ -0,0 +1 @@
+export class EmptyHandler{}

core/eventbus-decorator/test/fixtures/event-handle-with-context.ts

@@ -0,0 +1,28 @@
+import { Inject, SingletonProto } from '@eggjs/core-decorator';
+import {EventBus, Event, IEventContext, EventContext} from '../..';
+
+
+declare module '@eggjs/tegg' {
+  interface Events {
+    ctxEvent: (msg: string) => void;
+  }
+}
+
+@SingletonProto()
+export class EventContextProducer {
+  @Inject()
+  private readonly eventBus: EventBus;
+
+  trigger() {
+    this.eventBus.emit('ctxEvent', 'hello');
+  }
+}
+
+@Event('ctxEvent')
+export class EventContextHandler {
+  handle(@EventContext() ctx: IEventContext, msg: string): void {
+    console.log('ctx: ', ctx);
+    console.log('msg: ', msg);
+  }
+}
+

core/eventbus-decorator/test/fixtures/multiple-events-handle.ts

@@ -0,0 +1,29 @@
+import { Inject, SingletonProto } from '@eggjs/core-decorator';
+import { EventBus, Event } from '../..';
+
+
+declare module '@eggjs/tegg' {
+  interface Events {
+    hello: (msg: string) => void;
+    hi: (msg: string) => void;
+  }
+}
+
+@SingletonProto()
+export class MultiProducer {
+  @Inject()
+  private readonly eventBus: EventBus;
+
+  trigger() {
+    this.eventBus.emit('hello', 'Ydream');
+  }
+}
+
+@Event('hello')
+@Event('hi')
+export class MultiHandler {
+  handle(msg: string): void {
+    console.log('msg: ', msg);
+  }
+}
+

core/eventbus-runtime/src/EventHandlerFactory.ts

@@ -1,4 +1,4 @@
-import { EventHandler, EventName, Events } from '@eggjs/eventbus-decorator';
+import { EventHandler, EventName, Events, Arguments, EVENT_CONTEXT_INJECT } from '@eggjs/eventbus-decorator';
 import { EggContainerFactory } from '@eggjs/tegg-runtime';
 import { EggPrototype } from '@eggjs/tegg-metadata';
 import { MapUtil } from '@eggjs/tegg-common-util';
@@ -19,11 +19,33 @@ export class EventHandlerFactory {
     return this.handlerProtoMap.has(event);
   }
 
-  async getHandlers(event: EventName): Promise<Array<EventHandler<keyof Events>>> {
+  getHandlerProtos(event: EventName): Array<EggPrototype> {
     const handlerProtos = this.handlerProtoMap.get(event) || [];
-    const eggObjs = await Promise.all(handlerProtos.map(proto => {
-      return EggContainerFactory.getOrCreateEggObject(proto, proto.name);
+    return handlerProtos;
+  }
+
+  async getHandler(proto: EggPrototype): Promise<EventHandler<keyof Events>> {
+    const eggObj = await EggContainerFactory.getOrCreateEggObject(proto, proto.name);
+    return eggObj.obj as EventHandler<keyof Events>;
+  }
+
+  async getHandlers(event: EventName): Promise<Array<EventHandler<keyof Events>>> {
+    const handlerProtos = this.getHandlerProtos(event);
+    return await Promise.all(handlerProtos.map(proto => {
+      return this.getHandler(proto);
     }));
-    return eggObjs.map(t => t.obj as EventHandler<keyof Events>);
+  }
+
+  async handle(eventName: EventName, proto: EggPrototype, args: Arguments<any>): Promise<void> {
+    const handler = await this.getHandler(proto);
+    const enableInjectCtx = proto.getMetaData<boolean>(EVENT_CONTEXT_INJECT) ?? false;
+    if (enableInjectCtx) {
+      const ctx = {
+        eventName,
+      };
+      await Reflect.apply(handler.handle, handler, [ ctx, ...args ]);
+    } else {
+      await Reflect.apply(handler.handle, handler, args);
+    }
   }
 }

core/eventbus-runtime/src/SingletonEventBus.ts

@@ -1,5 +1,6 @@
 import { AccessLevel, Inject, SingletonProto } from '@eggjs/core-decorator';
 import { EventBus, Events, EventWaiter, EventName, CORK_ID } from '@eggjs/eventbus-decorator';
+import type { Arguments } from '@eggjs/eventbus-decorator';
 import { ContextHandler, EggContext } from '@eggjs/tegg-runtime';
 import type { EggLogger } from 'egg';
 import { EventContextFactory } from './EventContextFactory';
@@ -8,11 +9,6 @@ import { EventEmitter } from 'events';
 import awaitEvent from 'await-event';
 import awaitFirst from 'await-first';
 
-// from typed-emitter
-type Array<T> = [ T ] extends [ (...args: infer U) => any ]
-  ? U
-  : [ T ] extends [ void ] ? [] : [ T ];
-
 export interface Event {
   name: EventName;
   args: Array<any>;
@@ -56,15 +52,15 @@ export class SingletonEventBus implements EventBus, EventWaiter {
     return this;
   }
 
-  async await<E extends keyof Events>(event: E): Promise<Array<Events[E]>> {
+  async await<E extends keyof Events>(event: E): Promise<Arguments<Events[E]>> {
     return awaitEvent(this.emitter, event);
   }
 
-  awaitFirst<E extends keyof Events>(...e: Array<E>): Promise<{ event: EventName, args: Array<Events[E]> }> {
+  awaitFirst<E extends keyof Events>(...e: Array<E>): Promise<{ event: EventName, args: Arguments<Events[E]> }> {
     return awaitFirst(this.emitter, e);
   }
 
-  emit<E extends keyof Events>(event: E, ...args: Array<Events[E]>): boolean {
+  emit<E extends keyof Events>(event: E, ...args: Arguments<Events[E]>): boolean {
     const ctx = this.eventContextFactory.createContext();
     const hasListener = this.eventHandlerFactory.hasListeners(event);
     this.doEmit(ctx, event, args);
@@ -112,7 +108,7 @@ export class SingletonEventBus implements EventBus, EventWaiter {
     corkdEvents.events.push(event);
   }
 
-  emitWithContext<E extends keyof Events>(parentContext: EggContext, event: E, args: Array<Events[E]>): boolean {
+  emitWithContext<E extends keyof Events>(parentContext: EggContext, event: E, args: Arguments<Events[E]>): boolean {
     const corkId = parentContext.get(CORK_ID);
     const hasListener = this.eventHandlerFactory.hasListeners(event);
     if (corkId) {
@@ -145,13 +141,13 @@ export class SingletonEventBus implements EventBus, EventWaiter {
         await ctx.init(lifecycle);
       }
       try {
-        const handlers = await this.eventHandlerFactory.getHandlers(event);
-        await Promise.all(handlers.map(async handler => {
+        const handlerProtos = this.eventHandlerFactory.getHandlerProtos(event);
+        await Promise.all(handlerProtos.map(async proto => {
           try {
-            await Reflect.apply(handler.handle, handler, args);
+            await this.eventHandlerFactory.handle(event, proto, args);
           } catch (e) {
             // should wait all handlers done then destroy ctx
-            e.message = `[EventBus] process event ${String(event)} failed: ${e.message}`;
+            e.message = `[EventBus] process event ${String(event)} for handler ${String(proto.name)} failed: ${e.message}`;
             this.logger.error(e);
           }
         }));