DefinitelyTyped · typescript-bot · Feb 27, 2024 · Jan 24, 2024 · Jan 26, 2024 · Jan 28, 2024
diff --git a/types/newman/newman-tests.ts b/types/newman/newman-tests.ts
@@ -23,7 +23,7 @@ const workingDir = "path/to/working/directory";
 const insecureFileRead = true;
 const requestAgent = new http.Agent();
 
-// $ExpectType EventEmitter
+// $ExpectType EventEmitter<DefaultEventMap>
 run(
     {
         collection,

diff --git a/types/node-red/node-red-tests.ts b/types/node-red/node-red-tests.ts
@@ -23,7 +23,7 @@ async function REDTests() {
     // $ExpectType Util
     RED.util;
 
-    // $ExpectType EventEmitter
+    // $ExpectType EventEmitter<DefaultEventMap>
     RED.events;
 
     // $ExpectType Hooks

@@ -92,7 +92,30 @@ declare module "events" {
     interface StaticEventEmitterOptions {
         signal?: AbortSignal | undefined;
     }
-    interface EventEmitter extends NodeJS.EventEmitter {}
+    interface EventEmitter<T extends EventMap<T> = DefaultEventMap> extends NodeJS.EventEmitter<T> {}
+    type EventMap<T> = Record<keyof T, any[]> | DefaultEventMap;
+    type DefaultEventMap = [never];
+    const s: unique symbol;
+    type Key<K, T> = T extends DefaultEventMap ? string | symbol : K & (keyof (T & { [s]: never }));
+    type Key2<K, T> = T extends DefaultEventMap ? string | symbol : K & (keyof T);
+    type AnyRest = [...args: any[]];
+    type Args<K, T> = T extends DefaultEventMap ? AnyRest : (
+        K extends keyof T ? (
+                T[K] extends unknown[] ? T[K] : never
+            )
+            : never
+    );
+
+    type Listener<K, T, F> = T extends DefaultEventMap ? F : (
+        K extends keyof T ? (
+                T[K] extends unknown[] ? (...args: T[K]) => void : never
+            )
+            : never
+    );
+
+    type Listener1<K, T> = Listener<K, T, (...args: any[]) => void>;
+    type Listener2<K, T> = Listener<K, T, Function>;
+
     /**
      * The `EventEmitter` class is defined and exposed by the `node:events` module:
      *
@@ -106,10 +129,10 @@ declare module "events" {
      * It supports the following option:
      * @since v0.1.26
      */
-    class EventEmitter {
+    class EventEmitter<T extends EventMap<T> = DefaultEventMap> {
         constructor(options?: EventEmitterOptions);
 
-        [EventEmitter.captureRejectionSymbol]?(error: Error, event: string, ...args: any[]): void;
+        [EventEmitter.captureRejectionSymbol]?<K>(error: Error, event: Key<K, T>, ...args: Args<K, T>): void;
 
         /**
          * Creates a `Promise` that is fulfilled when the `EventEmitter` emits the given
@@ -536,13 +559,13 @@ declare module "events" {
     }
     global {
         namespace NodeJS {
-            interface EventEmitter {
-                [EventEmitter.captureRejectionSymbol]?(error: Error, event: string, ...args: any[]): void;
+            interface EventEmitter<T extends EventMap<T> = DefaultEventMap> {
+                [EventEmitter.captureRejectionSymbol]?<K>(error: Error, event: Key<K, T>, ...args: Args<K, T>): void;
                 /**
                  * Alias for `emitter.on(eventName, listener)`.
                  * @since v0.1.26
                  */
-                addListener(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                addListener<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Adds the `listener` function to the end of the listeners array for the
                  * event named `eventName`. No checks are made to see if the `listener` has
@@ -574,7 +597,7 @@ declare module "events" {
                  * @param eventName The name of the event.
                  * @param listener The callback function
                  */
-                on(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                on<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Adds a **one-time**`listener` function for the event named `eventName`. The
                  * next time `eventName` is triggered, this listener is removed and then invoked.
@@ -604,7 +627,7 @@ declare module "events" {
                  * @param eventName The name of the event.
                  * @param listener The callback function
                  */
-                once(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                once<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Removes the specified `listener` from the listener array for the event named`eventName`.
                  *
@@ -687,12 +710,12 @@ declare module "events" {
                  * Returns a reference to the `EventEmitter`, so that calls can be chained.
                  * @since v0.1.26
                  */
-                removeListener(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                removeListener<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Alias for `emitter.removeListener()`.
                  * @since v10.0.0
                  */
-                off(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                off<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Removes all listeners, or those of the specified `eventName`.
                  *
@@ -703,7 +726,7 @@ declare module "events" {
                  * Returns a reference to the `EventEmitter`, so that calls can be chained.
                  * @since v0.1.26
                  */
-                removeAllListeners(event?: string | symbol): this;
+                removeAllListeners(event?: Key<unknown, T>): this;
                 /**
                  * By default `EventEmitter`s will print a warning if more than `10` listeners are
                  * added for a particular event. This is a useful default that helps finding
@@ -732,7 +755,7 @@ declare module "events" {
                  * ```
                  * @since v0.1.26
                  */
-                listeners(eventName: string | symbol): Function[];
+                listeners<K>(eventName: Key<K, T>): Array<Listener2<K, T>>;
                 /**
                  * Returns a copy of the array of listeners for the event named `eventName`,
                  * including any wrappers (such as those created by `.once()`).
@@ -763,7 +786,7 @@ declare module "events" {
                  * ```
                  * @since v9.4.0
                  */
-                rawListeners(eventName: string | symbol): Function[];
+                rawListeners<K>(eventName: Key<K, T>): Array<Listener2<K, T>>;
                 /**
                  * Synchronously calls each of the listeners registered for the event named`eventName`, in the order they were registered, passing the supplied arguments
                  * to each.
@@ -804,7 +827,7 @@ declare module "events" {
                  * ```
                  * @since v0.1.26
                  */
-                emit(eventName: string | symbol, ...args: any[]): boolean;
+                emit<K>(eventName: Key<K, T>, ...args: Args<K, T>): boolean;
                 /**
                  * Returns the number of listeners listening for the event named `eventName`.
                  * If `listener` is provided, it will return how many times the listener is found
@@ -813,7 +836,7 @@ declare module "events" {
                  * @param eventName The name of the event being listened for
                  * @param listener The event handler function
                  */
-                listenerCount(eventName: string | symbol, listener?: Function): number;
+                listenerCount<K>(eventName: Key<K, T>, listener?: Listener2<K, T>): number;
                 /**
                  * Adds the `listener` function to the _beginning_ of the listeners array for the
                  * event named `eventName`. No checks are made to see if the `listener` has
@@ -831,7 +854,7 @@ declare module "events" {
                  * @param eventName The name of the event.
                  * @param listener The callback function
                  */
-                prependListener(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                prependListener<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Adds a **one-time**`listener` function for the event named `eventName` to the _beginning_ of the listeners array. The next time `eventName` is triggered, this
                  * listener is removed, and then invoked.
@@ -847,7 +870,7 @@ declare module "events" {
                  * @param eventName The name of the event.
                  * @param listener The callback function
                  */
-                prependOnceListener(eventName: string | symbol, listener: (...args: any[]) => void): this;
+                prependOnceListener<K>(eventName: Key<K, T>, listener: Listener1<K, T>): this;
                 /**
                  * Returns an array listing the events for which the emitter has registered
                  * listeners. The values in the array are strings or `Symbol`s.
@@ -867,7 +890,7 @@ declare module "events" {
                  * ```
                  * @since v6.0.0
                  */
-                eventNames(): Array<string | symbol>;
+                eventNames(): Array<(string | symbol) & Key2<unknown, T>>;
             }
         }
     }

@@ -11,6 +11,7 @@ import "./test/diagnostics_channel";
 import "./test/dns";
 import "./test/dom-events"; // dom-events behaves differently under lib-dom
 import "./test/events";
+import "./test/events_generic";
 import "./test/fs";
 import "./test/globals";
 import "./test/http";

@@ -163,3 +163,20 @@ async function test() {
     emitter.triggerAsyncId; // $ExpectType number
     emitter.emitDestroy();
 }
+
+{
+    class MyEmitter extends events.EventEmitter {
+        addListener(event: string, listener: () => void): this {
+            return this;
+        }
+        listeners(event: string): Array<() => void> {
+            return [];
+        }
+        emit(event: string, ...args: any[]): boolean {
+            return true;
+        }
+        listenerCount(type: string): number {
+            return 0;
+        }
+    }
+}