test: check that event emitters have error listeners in the same tick of their creation

Author: nbbeeken

src/change_stream.ts

@@ -630,6 +630,11 @@ export class ChangeStream<
     options: ChangeStreamOptions = {}
   ) {
     super();
+    const ctorCallSite = new Error('ChangeStream must add an error listener synchronously');
+    ctorCallSite.stack;
+
+    const squishErrorListenerRequirement = () => null;
+    this.on('error', squishErrorListenerRequirement);
 
     this.pipeline = pipeline;
     this.options = { ...options };
@@ -667,7 +672,11 @@ export class ChangeStream<
     // Listen for any `change` listeners being added to ChangeStream
     this.on('newListener', eventName => {
       if (eventName === 'change' && this.cursor && this.listenerCount('change') === 0) {
+        this.off('error', squishErrorListenerRequirement);
         this._streamEvents(this.cursor);
+        process.nextTick(() => {
+          if (this.listenerCount('error') === 0) throw ctorCallSite;
+        });
       }
     });
 

src/cmap/connection.ts

@@ -229,6 +229,7 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
 
   constructor(stream: Stream, options: ConnectionOptions) {
     super();
+    this.on('error', () => null);
 
     this.socket = stream;
     this.id = options.id;

src/cmap/connection_pool.ts

@@ -200,6 +200,7 @@ export class ConnectionPool extends TypedEventEmitter<ConnectionPoolEvents> {
 
   constructor(server: Server, options: ConnectionPoolOptions) {
     super();
+    this.on('error', () => null);
 
     this.options = Object.freeze({
       connectionType: Connection,

src/cursor/abstract_cursor.ts

@@ -267,6 +267,7 @@ export abstract class AbstractCursor<
     options: AbstractCursorOptions & Abortable = {}
   ) {
     super();
+    this.on('error', () => null);
 
     if (!client.s.isMongoClient) {
       throw new MongoRuntimeError('Cursor must be constructed with MongoClient');

src/mongo_client.ts

@@ -384,6 +384,7 @@ export class MongoClient extends TypedEventEmitter<MongoClientEvents> implements
 
   constructor(url: string, options?: MongoClientOptions) {
     super();
+    this.on('error', () => null);
 
     this.options = parseOptions(url, this, options);
 

src/mongo_types.ts

@@ -472,7 +472,12 @@ export class TypedEventEmitter<Events extends EventsDescription> extends EventEm
 }
 
 /** @public */
-export class CancellationToken extends TypedEventEmitter<{ cancel(): void }> {}
+export class CancellationToken extends TypedEventEmitter<{ cancel(): void }> {
+  constructor(...args: any[]) {
+    super(...args);
+    this.on('error', () => null);
+  }
+}
 
 /** @public */
 export type Abortable = {

src/sdam/monitor.ts

@@ -102,6 +102,7 @@ export class Monitor extends TypedEventEmitter<MonitorEvents> {
 
   constructor(server: Server, options: MonitorOptions) {
     super();
+    this.on('error', () => null);
 
     this.server = server;
     this.connection = null;

src/sdam/server.ts

@@ -142,6 +142,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
    */
   constructor(topology: Topology, description: ServerDescription, options: ServerOptions) {
     super();
+    this.on('error', () => null);
 
     this.serverApi = options.serverApi;
 

src/sessions.ts

@@ -161,6 +161,7 @@ export class ClientSession
     clientOptions: MongoOptions
   ) {
     super();
+    this.on('error', () => null);
 
     if (client == null) {
       // TODO(NODE-3483)

test/integration/change-streams/change_stream.test.ts

@@ -736,6 +736,7 @@ describe('Change Streams', function () {
           // ChangeStream detects emitter usage via 'newListener' event
           // so this covers all emitter methods
         });
+        changeStream.on('error', () => null); // one must listen for errors if they use EE mode.
 
         await once(changeStream.cursor, 'init');
         expect(changeStream).to.have.property('mode', 'emitter');
@@ -971,7 +972,7 @@ describe('Change Streams', function () {
           { requires: { topology: '!single' } },
           async function () {
             changeStream = collection.watch([]);
-            changeStream.on('change', sinon.stub());
+            changeStream.on('change', sinon.stub()).on('error', () => null);
 
             try {
               // eslint-disable-next-line @typescript-eslint/no-unused-vars