feat: allow ensureDelivery to be able to ensure delivery on emit

Signed-off-by: Remi Cattiau <remi@cattiau.com>

README.md

@@ -107,7 +107,7 @@ function sendWithAxios(message) {
 
 const emit = emitterFor(sendWithAxios, { mode: Mode.BINARY });
 // Set the emit
-Emitter.getSingleton().on("event", emit);
+Emitter.on("cloudevent", emit);
 
 ...
 // In any part of the code will send the event

src/event/cloudevent.ts

@@ -171,10 +171,11 @@ export class CloudEvent implements CloudEventV1, CloudEventV03 {
   /**
    * Emit this CloudEvent through the application
    *
-   * @return {CloudEvent} current CloudEvent object
+   * @param {boolean} ensureDelivery fail the promise if one listener fail
+   * @return {Promise<CloudEvent>} this
    */
-  public emit(): this {
-    Emitter.emitEvent(this);
+  public async emit(ensureDelivery = true): Promise<this> {
+    await Emitter.emitEvent(this, ensureDelivery);
     return this;
   }
 

src/index.ts

@@ -2,7 +2,7 @@ import { CloudEvent, Version } from "./event/cloudevent";
 import { ValidationError } from "./event/validation";
 import { CloudEventV03, CloudEventV03Attributes, CloudEventV1, CloudEventV1Attributes } from "./event/interfaces";
 
-import { Options, TransportFunction, EmitterFunction, emitterFor } from "./transport/emitter";
+import { Options, TransportFunction, EmitterFunction, emitterFor, Emitter } from "./transport/emitter";
 import { Headers, Mode, Binding, HTTP, Message, Serializer, Deserializer } from "./message";
 
 import CONSTANTS from "./constants";
@@ -28,6 +28,7 @@ export {
   TransportFunction,
   EmitterFunction,
   emitterFor,
+  Emitter,
   Options,
   // From Constants
   CONSTANTS,

src/transport/emitter.ts

@@ -67,7 +67,7 @@ export class Emitter extends EventEmitter {
   /**
    * Singleton store
    */
-  static singleton: Emitter | undefined = undefined;
+  static instance: Emitter | undefined = undefined;
 
   /**
    * Create an Emitter
@@ -83,20 +83,42 @@ export class Emitter extends EventEmitter {
    *
    * @return {Emitter} return Emitter singleton
    */
-  static getSingleton(): Emitter {
-    if (!Emitter.singleton) {
-      Emitter.singleton = new Emitter();
+  static getInstance(): Emitter {
+    if (!Emitter.instance) {
+      Emitter.instance = new Emitter();
     }
-    return Emitter.singleton;
+    return Emitter.instance;
+  }
+
+  /**
+   * Add a listener for eventing
+   *
+   * @param {string} event type to listen to
+   * @param {Function} listener to call on event
+   * @return {void}
+   */
+  static on(event: "cloudevent" | "newListener" | "removeListener", listener: (...args: any[]) => void): void {
+    this.getInstance().on(event, listener);
   }
 
   /**
    * Emit an event inside this application
    *
    * @param {CloudEvent} event to emit
+   * @param {boolean} ensureDelivery fail the promise if one listener fail
    * @return {void}
    */
-  static emitEvent(event: CloudEvent): void {
-    this.getSingleton().emit("event", event);
+  static async emitEvent(event: CloudEvent, ensureDelivery = true): Promise<void> {
+    if (!ensureDelivery) {
+      // Ensure delivery is disabled so we don't wait for Promise
+      Emitter.getInstance().emit("cloudevent", event);
+    } else {
+      // Execute all listeners and wrap them in a Promise
+      await Promise.all(
+        Emitter.getInstance()
+          .listeners("cloudevent")
+          .map(async (l) => l(event)),
+      );
+    }
   }
 }

test/integration/emitter_singleton_test.ts

@@ -0,0 +1,55 @@
+import "mocha";
+
+import { emitterFor, HTTP, Mode, Message, Emitter } from "../../src";
+
+import { fixture, assertStructured } from "./emitter_factory_test";
+
+import { rejects, doesNotReject } from "assert";
+
+describe("Emitter Singleton", () => {
+  it("emit a Node.js 'cloudevent' event as an EventEmitter", async () => {
+    const msg: Message | unknown = await new Promise((resolve) => {
+      const fn = async (message: Message) => {
+        resolve(message);
+      };
+      const emitter = emitterFor(fn, { binding: HTTP, mode: Mode.STRUCTURED });
+      Emitter.on("cloudevent", emitter);
+
+      fixture.emit(false);
+    });
+    let body: unknown = (<Message>(<unknown>msg)).body;
+    if (typeof body === "string") {
+      body = JSON.parse(body);
+    }
+    assertStructured({ ...(<any>body), ...(<Message>(<unknown>msg)).headers });
+  });
+
+  it("emit a Node.js 'cloudevent' event as an EventEmitter with ensureDelivery", async () => {
+    let msg: Message | unknown = undefined;
+    const fn = async (message: Message) => {
+      msg = message;
+    };
+    const emitter = emitterFor(fn, { binding: HTTP, mode: Mode.STRUCTURED });
+    Emitter.on("cloudevent", emitter);
+    await fixture.emit(true);
+    let body: any = (<Message>msg).body;
+    if (typeof body === "string") {
+      body = JSON.parse(body);
+    }
+    assertStructured({ ...(<any>body), ...(<Message>(<unknown>msg)).headers });
+  });
+
+  it("emit a Node.js 'cloudevent' event as an EventEmitter with ensureDelivery Error", async () => {
+    const emitter = async () => {
+      throw new Error("Not sent");
+    };
+    Emitter.on("cloudevent", emitter);
+    // Should fail with emitWithEnsureDelivery
+    await rejects(() => fixture.emit(true));
+    // Should not fail with emitWithEnsureDelivery
+    // Work locally but not on Github Actions
+    if (!process.env.GITHUB_WORKFLOW) {
+      await doesNotReject(() => fixture.emit(false));
+    }
+  });
+});