fix(ClientRequest): remove passthrough socket listeners on close

src/interceptors/ClientRequest/MockHttpSocket.ts

@@ -13,7 +13,6 @@ import { MockSocket } from '../Socket/MockSocket'
 import type { NormalizedSocketWriteArgs } from '../Socket/utils/normalizeSocketWriteArgs'
 import { isPropertyAccessible } from '../../utils/isPropertyAccessible'
 import { baseUrlFromConnectionOptions } from '../Socket/utils/baseUrlFromConnectionOptions'
-import { createServerErrorResponse } from '../../utils/responseUtils'
 import { createRequestId } from '../../createRequestId'
 import { getRawFetchHeaders } from './utils/recordRawHeaders'
 import { FetchResponse } from '../../utils/fetchUtils'
@@ -207,9 +206,18 @@ export class MockHttpSocket extends MockSocket {
       })
     }
 
-    // If the developer destroys the socket, destroy the original connection.
-    this.once('error', (error) => {
-      socket.destroy(error)
+    // The client-facing socket can be destroyed in two ways:
+    // 1. The developer destroys the socket.
+    // 2. The passthrough socket "close" is forwarded to the socket.
+    this.once('close', () => {
+      socket.removeAllListeners()
+
+      // If the closure didn't originate from the passthrough socket, destroy it.
+      if (!socket.destroyed) {
+        socket.destroy()
+      }
+
+      this.originalSocket = undefined
     })
 
     this.address = socket.address.bind(socket)

test/modules/http/compliance/http-socket-listeners.test.ts

@@ -0,0 +1,57 @@
+// @vitest-environment node
+/**
+ * @see https://github.com/mswjs/msw/issues/2537
+ * @see https://github.com/mswjs/interceptors/pull/755
+ */
+import { it, expect, beforeAll, afterAll } from 'vitest'
+import http from 'node:http'
+import { Socket } from 'node:net'
+import { HttpServer } from '@open-draft/test-server/http'
+import { DeferredPromise } from '@open-draft/deferred-promise'
+import { ClientRequestInterceptor } from '../../../../src/interceptors/ClientRequest'
+import { waitForClientRequest } from '../../../helpers'
+
+const httpServer = new HttpServer((app) => {
+  app.get('/resource', async (req, res) => {
+    res.send('ok')
+  })
+})
+
+const interceptor = new ClientRequestInterceptor()
+
+beforeAll(async () => {
+  interceptor.apply()
+  await httpServer.listen()
+})
+
+afterAll(async () => {
+  interceptor.dispose()
+  await httpServer.close()
+})
+
+it('removes all event listeners from a passthrough socket after closing', async () => {
+  const request = http.get(httpServer.http.url('/resource'), {
+    headers: { connection: 'close' },
+  })
+  const pendingSocket = new DeferredPromise<Socket>()
+
+  request.once('socket', (socket) => {
+    pendingSocket.resolve(socket)
+  })
+
+  const socket = await pendingSocket
+  const { res, text } = await waitForClientRequest(request)
+
+  expect.soft(res.statusCode).toBe(200)
+  await expect.soft(text()).resolves.toBe('ok')
+
+  const passthroughSocket = Reflect.get(socket, 'originalSocket') as Socket
+  expect(passthroughSocket).toBeInstanceOf(Socket)
+
+  await expect
+    .poll(
+      // @ts-expect-error Node.js internals
+      () => passthroughSocket._events
+    )
+    .toEqual({})
+})

test/modules/http/compliance/http-timeout.test.ts

@@ -1,6 +1,4 @@
-/**
- * @vitest-environment node
- */
+// @vitest-environment node
 import { vi, it, expect, beforeAll, afterEach, afterAll } from 'vitest'
 import http from 'node:http'
 import { HttpServer } from '@open-draft/test-server/http'