http: fix leaked error listener on sync HTTP req create + destroy

doc/api/http.md

@@ -957,7 +957,8 @@ changes:
 
 Destroy the request. Optionally emit an `'error'` event,
 and emit a `'close'` event. Calling this will cause remaining data
-in the response to be dropped and the socket to be destroyed.
+in the response to be dropped, and the socket to be destroyed if used,
+or returned to the corresponding Agent pool otherwise if possible.
 
 See [`writable.destroy()`][] for further details.
 

lib/_http_client.js

@@ -999,6 +999,7 @@ function onSocketNT(req, socket, err) {
     if (socket) {
       if (!err && req.agent && !socket.destroyed) {
         socket.emit('free');
+        socket.removeListener('error', socketErrorListener);
       } else {
         finished(socket.destroy(err || req[kError]), (er) => {
           if (er?.code === 'ERR_STREAM_PREMATURE_CLOSE') {

test/parallel/test-http-client-request-listeners-leak.js

@@ -0,0 +1,50 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+const { defaultMaxListeners } = require('events');
+
+// Immediately destroying an HTTP request must not leak listeners on the
+// freed socket. When sockets are reused via a keep-alive agent leaked
+// listeners would accumulate to trigger a MaxListenersExceededWarning.
+
+// Check we don't get a MaxListenersExceededWarning:
+process.on('warning', common.mustNotCall('Unexpected warning emitted'));
+
+const server = http.createServer(common.mustNotCall());
+
+server.listen(0, common.mustCall(() => {
+  const agent = new http.Agent({ keepAlive: true });
+  const port = server.address().port;
+
+  // Count actual socket creations to confirm reuse:
+  let createSocketCount = 0;
+  const origCreateSocket = agent.createSocket.bind(agent);
+  agent.createSocket = function(...args) {
+    createSocketCount++;
+    return origCreateSocket(...args);
+  };
+
+  function executeHttpGet() {
+    return new Promise((resolve) => {
+      const req = http.get({ host: '127.0.0.1', port, agent });
+      req.on('error', resolve);
+      req.on('close', resolve);
+      req.on('response', common.mustNotCall());
+      req.destroy();
+    });
+  }
+
+  async function main() {
+    for (let i = 0; i < defaultMaxListeners + 1; i++) {
+      await executeHttpGet();
+    }
+
+    assert.strictEqual(createSocketCount, 1);
+
+    server.close();
+    agent.destroy();
+  }
+
+  main().then(common.mustCall());
+}));