[fix] Do not rely on undocumented behavior

Use the chunk returned by `socket.read()` to handle the buffered data
instead of relying on a `'data'` event emitted after the `'close'`
event.

Refs: nodejs/node#39639

lib/websocket.js

@@ -1002,24 +1002,33 @@ function socketOnClose() {
   const websocket = this[kWebSocket];
 
   this.removeListener('close', socketOnClose);
+  this.removeListener('data', socketOnData);
   this.removeListener('end', socketOnEnd);
 
   websocket._readyState = WebSocket.CLOSING;
 
+  let chunk;
+
   //
   // The close frame might not have been received or the `'end'` event emitted,
   // for example, if the socket was destroyed due to an error. Ensure that the
   // `receiver` stream is closed after writing any remaining buffered data to
   // it. If the readable side of the socket is in flowing mode then there is no
   // buffered data as everything has been already written and `readable.read()`
   // will return `null`. If instead, the socket is paused, any possible buffered
-  // data will be read as a single chunk and emitted synchronously in a single
-  // `'data'` event.
+  // data will be read as a single chunk.
   //
-  websocket._socket.read();
+  if (
+    !this._readableState.endEmitted &&
+    !websocket._closeFrameReceived &&
+    !websocket._receiver._writableState.errorEmitted &&
+    (chunk = websocket._socket.read()) !== null
+  ) {
+    websocket._receiver.write(chunk);
+  }
+
   websocket._receiver.end();
 
-  this.removeListener('data', socketOnData);
   this[kWebSocket] = undefined;
 
   clearTimeout(websocket._closeTimer);

test/websocket.test.js

@@ -10,6 +10,7 @@ const tls = require('tls');
 const fs = require('fs');
 const { URL } = require('url');
 
+const Sender = require('../lib/sender');
 const WebSocket = require('..');
 const { GUID, NOOP } = require('../lib/constants');
 
@@ -2735,15 +2736,21 @@ describe('WebSocket', () => {
       });
     });
 
-    it('consumes all received data when connection is closed abnormally', (done) => {
+    it('consumes all received data when connection is closed (1/2)', (done) => {
       const wss = new WebSocket.Server(
         {
           perMessageDeflate: { threshold: 0 },
           port: 0
         },
         () => {
-          const ws = new WebSocket(`ws://localhost:${wss.address().port}`);
           const messages = [];
+          const ws = new WebSocket(`ws://localhost:${wss.address().port}`);
+
+          ws.on('open', () => {
+            ws._socket.on('close', () => {
+              assert.strictEqual(ws._receiver._state, 5);
+            });
+          });
 
           ws.on('message', (message) => messages.push(message));
           ws.on('close', (code) => {
@@ -2762,6 +2769,76 @@ describe('WebSocket', () => {
       });
     });
 
+    it('consumes all received data when connection is closed (2/2)', (done) => {
+      const payload1 = Buffer.alloc(15 * 1024);
+      const payload2 = Buffer.alloc(1);
+
+      const opts = {
+        fin: true,
+        opcode: 0x02,
+        mask: false,
+        readOnly: false
+      };
+
+      const list = [
+        ...Sender.frame(payload1, { rsv1: false, ...opts }),
+        ...Sender.frame(payload2, { rsv1: true, ...opts })
+      ];
+
+      for (let i = 0; i < 399; i++) {
+        list.push(list[list.length - 2], list[list.length - 1]);
+      }
+
+      const data = Buffer.concat(list);
+
+      const wss = new WebSocket.Server(
+        {
+          perMessageDeflate: true,
+          port: 0
+        },
+        () => {
+          const messageLengths = [];
+          const ws = new WebSocket(`ws://localhost:${wss.address().port}`);
+
+          ws.on('open', () => {
+            ws._socket.prependListener('close', () => {
+              assert.strictEqual(ws._receiver._state, 5);
+              assert.strictEqual(ws._socket._readableState.length, 3);
+            });
+
+            const push = ws._socket.push;
+
+            ws._socket.push = (data) => {
+              ws._socket.push = push;
+              ws._socket.push(data);
+              ws.terminate();
+            };
+
+            // This hack is used because there is no guarantee that more than
+            // 16 KiB will be sent as a single TCP packet.
+            push.call(ws._socket, data);
+
+            wss.clients
+              .values()
+              .next()
+              .value.send(payload2, { compress: false });
+          });
+
+          ws.on('message', (message) => {
+            messageLengths.push(message.length);
+          });
+
+          ws.on('close', (code) => {
+            assert.strictEqual(code, 1006);
+            assert.strictEqual(messageLengths.length, 402);
+            assert.strictEqual(messageLengths[0], 15360);
+            assert.strictEqual(messageLengths[messageLengths.length - 1], 1);
+            wss.close(done);
+          });
+        }
+      );
+    });
+
     it('handles a close frame received while compressing data', (done) => {
       const wss = new WebSocket.Server(
         {