When emitting from timeout() prepend timeout error

lib/index.ts

@@ -1,6 +1,6 @@
-import { url } from "./url.js";
-import { Manager, ManagerOptions } from "./manager.js";
-import { Socket, SocketOptions } from "./socket.js";
+import { url } from "./url";
+import { Manager, ManagerOptions } from "./manager";
+import { Socket, SocketOptions } from "./socket";
 import debugModule from "debug"; // debug()
 
 const debug = debugModule("socket.io-client"); // debug()

lib/manager.ts

@@ -4,11 +4,11 @@ import {
   installTimerFunctions,
   nextTick,
 } from "engine.io-client";
-import { Socket, SocketOptions, DisconnectDescription } from "./socket.js";
+import { Socket, SocketOptions, DisconnectDescription } from "./socket";
 import * as parser from "socket.io-parser";
 import { Decoder, Encoder, Packet } from "socket.io-parser";
-import { on } from "./on.js";
-import { Backoff } from "./contrib/backo2.js";
+import { on } from "./on";
+import { Backoff } from "./contrib/backo2";
 import {
   DefaultEventsMap,
   EventsMap,

lib/socket.ts

@@ -1,6 +1,6 @@
 import { Packet, PacketType } from "socket.io-parser";
-import { on } from "./on.js";
-import { Manager } from "./manager.js";
+import { on } from "./on";
+import { Manager } from "./manager";
 import {
   DefaultEventsMap,
   EventNames,
@@ -12,6 +12,46 @@ import debugModule from "debug"; // debug()
 
 const debug = debugModule("socket.io-client:socket"); // debug()
 
+/**
+ * Utulity type to extract the last element of a tuple.
+ */
+type Last<T extends any[]> = T["length"] extends 1
+  ? T
+  : T extends [infer H, ...infer Rest]
+  ? Last<Rest>
+  : [];
+/**
+ * Utility type to extract all elements of a tuple except the last one.
+ */
+type AllButLast<T extends any[]> = T extends [...infer I, infer L] ? I : never;
+
+/**
+ * Utility type to prepend the timeout error to a parameter list.
+ */
+type PrependTimeoutError<T extends any[]> = {
+  [K in keyof T]: T[K] extends (...args: infer Params) => infer Result
+    ? (timeoutErr: Error, ...args: Params) => Result
+    : T[K];
+};
+
+/**
+ * Utility type to decorate callbacks of each method in an interface with a timeout error.
+ */
+type DecorateCallbacksWithTimeoutError<T> = {
+  [K in keyof T]: T[K] extends (...args: infer Params) => infer Result
+    ? (
+        ...args: [
+          ...AllButLast<Params>,
+          ...(PrependTimeoutError<
+            Last<Params>
+          > extends infer Z extends readonly unknown[]
+            ? Z
+            : never)
+        ]
+      ) => Result
+    : T[K];
+};
+
 export interface SocketOptions {
   /**
    * the authentication payload sent when connecting to the Namespace
@@ -677,7 +717,9 @@ export class Socket<
    *
    * @returns self
    */
-  public timeout(timeout: number): this {
+  public timeout(
+    timeout: number
+  ): Socket<ListenEvents, DecorateCallbacksWithTimeoutError<EmitEvents>> {
     this.flags.timeout = timeout;
     return this;
   }

package.json

@@ -48,7 +48,7 @@
     "@rollup/plugin-node-resolve": "^13.0.5",
     "@sinonjs/fake-timers": "^7.1.2",
     "@types/mocha": "^9.0.0",
-    "@types/node": "^16.7.6",
+    "@types/node": "^18.11.18",
     "@types/sinonjs__fake-timers": "^6.0.3",
     "@wdio/cli": "^7.26.0",
     "@wdio/local-runner": "^7.26.0",
@@ -72,7 +72,7 @@
     "ts-loader": "^8.3.0",
     "ts-node": "^10.2.1",
     "tsd": "^0.17.0",
-    "typescript": "^4.4.2"
+    "typescript": "^4.9.4"
   },
   "scripts": {
     "compile": "rimraf ./build && tsc && tsc -p tsconfig.esm.json && ./postcompile.sh",