http: emit ServerResponse 'close' on client disconnect

When the canUseInternalAssignSocket fast path is taken,
assignSocketInternal stores onServerResponseClose on the socket via
setCloseCallback (socket[kCloseCallback] = ...) instead of registering
a real EventEmitter listener. Nothing was invoking that stored
callback when the socket's underlying handle closed, so
ServerResponse.on('close', ...) never ran on client abort.

Fire callCloseCallback(this) at the end of NodeHTTPServerSocket#onClose
after the request destroy, mirroring what Node's socket.on('close')
listener does. This covers both the mid-response case (#29219) and
the no-write case (#14697).

Fixes #29219
Fixes #14697

Author: robobun

src/js/node/_http_server.ts

@@ -908,6 +908,12 @@ const NodeHTTPServerSocket = class Socket extends Duplex {
         req.destroy();
       }
     }
+
+    // Fire the close callback set by assignSocketInternal
+    // (onServerResponseClose). This forwards the socket close to the
+    // attached ServerResponse so `res.on("close", ...)` runs on client
+    // disconnect, matching Node.js. See issues #29219, #14697.
+    callCloseCallback(this);
   }
   #onCloseForDestroy(closeCallback) {
     this.#onClose();

test/regression/issue/29219.test.ts

@@ -0,0 +1,86 @@
+// https://github.com/oven-sh/bun/issues/29219
+import { expect, test } from "bun:test";
+import http from "node:http";
+import net from "node:net";
+
+test("ServerResponse emits 'close' when the client aborts mid-response", async () => {
+  const { promise, resolve } = Promise.withResolvers<{
+    resClosed: boolean;
+    reqErrored: boolean;
+  }>();
+
+  let resClosed = false;
+  let reqErrored = false;
+
+  const server = http.createServer((req, res) => {
+    res.on("close", () => {
+      resClosed = true;
+    });
+
+    // Write some data so the response is mid-stream when the client aborts.
+    res.write("hello\n");
+
+    req.on("error", () => {
+      reqErrored = true;
+      server.close(() => {
+        resolve({ resClosed, reqErrored });
+      });
+    });
+  });
+
+  await new Promise<void>(done => {
+    server.listen(0, "127.0.0.1", () => {
+      const { port } = server.address() as net.AddressInfo;
+      const client = net.createConnection({ port, host: "127.0.0.1" }, () => {
+        client.write("GET / HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n");
+        client.on("data", () => {
+          client.end(); // force abort mid-response
+        });
+      });
+      done();
+    });
+  });
+
+  const result = await promise;
+  expect(result).toEqual({ resClosed: true, reqErrored: true });
+});
+
+// Also covers https://github.com/oven-sh/bun/issues/14697 — same root
+// cause, but the handler never writes a response before the client
+// disconnects. Pre-fix, only `req.on("close")` fired.
+test("ServerResponse emits 'close' when the client aborts before any write", async () => {
+  const { promise, resolve } = Promise.withResolvers<{
+    resClosed: boolean;
+    reqClosed: boolean;
+  }>();
+
+  let resClosed = false;
+  let reqClosed = false;
+
+  const server = http.createServer((req, res) => {
+    res.once("close", () => {
+      resClosed = true;
+      if (reqClosed) server.close(() => resolve({ resClosed, reqClosed }));
+    });
+    req.once("close", () => {
+      reqClosed = true;
+      if (resClosed) server.close(() => resolve({ resClosed, reqClosed }));
+    });
+    // Deliberately don't write or end — wait for the client to go away.
+  });
+
+  await new Promise<void>(done => {
+    server.listen(0, "127.0.0.1", () => {
+      const { port } = server.address() as net.AddressInfo;
+      const client = net.createConnection({ port, host: "127.0.0.1" }, () => {
+        client.write("GET / HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n");
+        // Wait a tick so the server receives the request, then yank the socket.
+        setTimeout(() => client.destroy(), 100);
+      });
+      done();
+    });
+  });
+
+  const result = await promise;
+  expect(result).toEqual({ resClosed: true, reqClosed: true });
+});