fix(websocket): preserve failed connection error message

lib/web/websocket/connection.js

@@ -314,6 +314,8 @@ function failWebsocketConnection (handler, code, reason, cause) {
 
   handler.controller.abort()
 
+  handler.closeReason = reason
+
   if (isConnecting(handler.readyState)) {
     // If the connection was not established, we must still emit an 'error' and 'close' events
     handler.onSocketClose()

lib/web/websocket/websocket.js

@@ -52,6 +52,7 @@ function getSocketAddress (socket) {
  * @property {number} readyState
  * @property {import('stream').Duplex} socket
  * @property {Set<number>} closeState
+ * @property {string} [closeReason]
  * @property {import('../fetch/index').Fetch} controller
  * @property {boolean} [wasEverConnected=false]
  */
@@ -113,6 +114,7 @@ class WebSocket extends EventTarget {
     readyState: states.CONNECTING,
     socket: null,
     closeState: new Set(),
+    closeReason: '',
     controller: null,
     wasEverConnected: false
   }
@@ -579,7 +581,7 @@ class WebSocket extends EventTarget {
       this.#handler.closeState.has(sentCloseFrameState.RECEIVED)
 
     let code = 1005
-    let reason = ''
+    let reason = this.#handler.closeReason ?? ''
 
     const result = this.#parser?.closingInfo
 
@@ -604,7 +606,8 @@ class WebSocket extends EventTarget {
       code = 1006
 
       fireEvent('error', this, (type, init) => new ErrorEvent(type, init), {
-        error: new TypeError(reason)
+        error: new TypeError(reason),
+        message: reason
       })
     }
 

test/websocket/issue-4735.js

@@ -0,0 +1,18 @@
+'use strict'
+
+const { test } = require('node:test')
+const { WebSocket } = require('../..')
+const { once } = require('node:events')
+
+test('WebSocket emits error with message when connection cannot be opened', async (t) => {
+  t.plan(2)
+
+  const ws = new WebSocket('ws://localhost:1')
+
+  ws.addEventListener('error', ({ error, message }) => {
+    t.assert.strictEqual(error.message, 'Received network error or non-101 status code.')
+    t.assert.strictEqual(message, 'Received network error or non-101 status code.')
+  })
+
+  await once(ws, 'close')
+})