test: keep the accepted socket's buffer empty in the paused peer-reset tests

.claude/docs/landing-prs.md

@@ -38,7 +38,7 @@ Companion to the "Landing PRs: What Bun Reviewers Catch" section in CLAUDE.md. T
 
 - **Never assume OS/ABI facts are portable.** errno meanings differ (EPERM is a sharing violation on Windows), event flags differ, Windows env vars are case-insensitive, Windows has no POSIX signals, blocking syscalls retry on EINTR. FFI/ABI: explicit calling conventions on BOTH sides; fixed-width or C-ABI types, never bare int read from c_ulong (LLP64 garbage on Windows); extern declarations diff'd parameter-by-parameter against definitions — they compile cleanly per side and crash only on the platform you didn't build; complete Windows error-translation tables with fallbacks instead of force-unwraps.
 - **Platform parity is part of every fix.** When you fix one platform backend (POSIX vs kqueue vs epoll vs libuv), audit every sibling backend for the same defect and apply symmetrically — or state why a backend is unaffected ("kqueue register path is unhandled. You only patched unregister."). A POSIX-only API addition ships its Windows equivalent in the same PR. Enabling a feature on a new platform means grepping every gate, dispatch chain, parallel platform script, test skip, and allowlist. Platform-specific CI failures in files you touched are real merge-blocking bugs, never flakes. Comment WHY on every new platform exclusion.
-- **Write tests to pass on every CI platform** (Windows, macOS x64+arm64, Linux glibc and musl). Split on `/\r?\n/` (Windows CRLF); normalize separators in path assertions; never spawn shell builtins (echo, sleep are not programs on Windows — use bunExe() -e); no hardcoded /tmp or /bin; incidental servers bind 127.0.0.1, never ::1 (CI Linux may lack IPv6 — IPv6-specific tests gate on the harness IPv6 helper); exit codes not signal names for "did not crash" (Windows has no signals); when probing a limit, exceed the LARGEST platform limit to trip the guard and stay under the SMALLEST when constructing inputs (macOS PATH_MAX is 1024). Before skipping a platform, verify it genuinely lacks the capability (Windows supports AF_UNIX). Skip narrowly via test.skipIf with a reason; never fix one platform by loosening assertions for all.
+- **Write tests to pass on every CI platform** (Windows, macOS x64+arm64, Linux glibc and musl). Split on `/\r?\n/` (Windows CRLF); normalize separators in path assertions; never spawn shell builtins (echo, sleep are not programs on Windows — use bunExe() -e); no hardcoded /tmp or /bin; incidental servers bind 127.0.0.1, never ::1 (CI Linux may lack IPv6 — IPv6-specific tests gate on the harness IPv6 helper); exit codes not signal names for "did not crash" (Windows has no signals); when probing a limit, exceed the LARGEST platform limit to trip the guard and stay under the SMALLEST when constructing inputs (macOS PATH_MAX is 1024); a test that asserts a peer's RST is reported must send the RST to a socket whose receive buffer is empty (or that reads before the reset): macOS answers an RST with an ACK instead of resetting while unread bytes sit in the buffer, depending on timing, and a socket that never reads gets no second chance (see the "server socket whose peer resets the connection" tests in test/js/node/tls/node-tls-server.test.ts). Before skipping a platform, verify it genuinely lacks the capability (Windows supports AF_UNIX). Skip narrowly via test.skipIf with a reason; never fix one platform by loosening assertions for all.
 - **Decide explicitly: filesystem path or URL-like identifier.** Module specifiers, cache keys, sourcemap paths use forward slashes everywhere (posix path helpers). Filesystem paths use platform path APIs, never literal '/' concatenation. Windows: accept BOTH separators; drive-relative (C:foo) and UNC forms exist; PATH splits on ';'. On POSIX, backslash is a legal filename character. Splitting a posix-normalized string with the platform separator silently no-ops on Windows — feed the other separator style through every new API in tests.
 - **Beyond `rust:check-all` (required by CLAUDE.md) for platform-gated code:** verify link-time symbol resolution (a POSIX extern must still resolve on Windows even if runtime-gated); audit enum switches duplicated across platform arms; distrust lint sweeps — a cast redundant on your host may be load-bearing on another target. Trick: flip the platform condition locally to force the other branch through the type-checker.
 

test/js/bun/net/socket.test.ts

@@ -4169,11 +4169,11 @@
   const readReset = { reported: true, code: "ECONNRESET", syscall: "read" };
 
   describe.each(["tcp", "tls"] as const)("%s", transport => {
     // The peer lives in a child process that is killed while data it never read sits
     // in its receive buffer: the kernel then closes its socket with an RST, and
-    // nothing (no FIN, and for TLS no close_notify) is queued ahead of the reset. An
-    // in-process terminate() is not usable for the TLS case: it writes a close_notify
-    // first, and on POSIX the reading side consumes that as a clean end.
+    // nothing (no FIN, and for TLS no close_notify) is queued ahead of the reset,
+    // whatever Bun's own terminate() sends (until #39632 it sent a close_notify first
+    // for TLS, which the reading side consumed as a clean end).
     const peerSource = `
       await Bun.connect({
         hostname: "127.0.0.1",

test/js/node/tls/node-tls-server.test.ts

@@ -2458,12 +2458,19 @@
   });
 });
 
-describe.each(["tls", "net"])("%s server socket whose peer resets the connection behind unread data", transport => {
-  // The peer sends data while the accepted socket is paused, then resets the
-  // connection (RST) instead of ending it. Node reports that as a read
-  // error and never emits 'end'. allowHalfOpen keeps the accepted socket open
-  // after an 'end', so a reset misreported as an orderly end strands it.
-  async function acceptPausedSocketAndFill() {
+describe.each(["tls", "net"])("%s server socket whose peer resets the connection", transport => {
+  // The peer resets the connection (RST) instead of ending it while the accepted
+  // socket is paused. Node reports that as a read error and never emits 'end'.
+  // allowHalfOpen keeps the accepted socket open after an 'end', so a reset
+  // misreported as an orderly end strands it.
+  //
+  // Whether macOS delivers a reset to a socket that holds unread bytes depends on
+  // timing: filling the buffers first (the original shape of these tests) lost it
+  // nearly every time, and even 296 unread bytes lost it in up to 17 of 40 attempts
+  // when the RST came a few milliseconds later. With an empty buffer it is never
+  // lost, so only the test that is about the unread bytes sends any, and it sends
+  // them right before the reset. Linux and Windows deliver it either way.
+  async function acceptPausedSocket() {
     const accepted = Promise.withResolvers<net.Socket>();
     const onConnection = (socket: net.Socket) => {
       socket.pause();
@@ -2476,6 +2483,7 @@
     await once(server.listen(0, "127.0.0.1"), "listening");
 
     const peerReady = Promise.withResolvers<void>();
+    const peerGotData = Promise.withResolvers<void>();
     const peer = await Bun.connect({
       hostname: "127.0.0.1",
       port: (server.address() as AddressInfo).port,
@@ -2488,7 +2496,9 @@
           if (success) peerReady.resolve();
           else peerReady.reject(verifyError ?? new Error("handshake failed"));
         },
-        data() {},
+        data() {
+          peerGotData.resolve();
+        },
         close() {},
         error(_peer, error) {
           peerReady.reject(error);
@@ -2519,47 +2529,48 @@
     // Paused again: the 'data' listener above switched the stream to flowing.
     socket.pause();
 
-    const t = {
+    return {
       socket,
       peer,
       events,
+      peerGotData: peerGotData.promise,
       bytesRead: () => bytes,
       settled: settled.promise,
       [Symbol.dispose]() {
         socket.destroy();
         server.close();
       },
     };
-    // One chunk that fits: it is queued ahead of the reset and the receive window
-    // stays open. macOS drops an RST that arrives at a zero window, so filling
-    // the buffers would strand the socket there.
-    const chunk = Buffer.alloc(64 * 1024, "r");
-    const written = peer.write(chunk);
-    if (written !== chunk.length) {
-      t[Symbol.dispose]();
-      throw new Error(`short write: ${written} of ${chunk.length}`);
-    }
-    return t;
   }
 
   it("reports the reset that arrives while the socket is paused as ECONNRESET, not 'end'", async () => {
-    using t = await acceptPausedSocketAndFill();
+    using t = await acceptPausedSocket();
+    // A round trip to the peer after the pause: this process has polled since, so
+    // the reset has to reach the paused socket on its own and cannot ride on the
+    // writable event that a pause leaves behind. The peer sends nothing back.
+    t.socket.write("still here");
+    await t.peerGotData;
     t.peer.terminate();
     await t.settled;
     expect(t.events).toEqual(["error ECONNRESET", "close hadError=true"]);
   });
 
   it("delivers the data queued ahead of the reset and then reports ECONNRESET, not 'end'", async () => {
-    using t = await acceptPausedSocketAndFill();
-    // Both happen before the event loop runs again, so the socket's next read
-    // event carries the queued data and the reset together: the read loop drains
-    // the data and then gets the error from recv().
+    using t = await acceptPausedSocket();
+    // One chunk that fits in the buffers, then all three happen before the event
+    // loop runs again: the socket's next read event carries the queued data and the
+    // reset together, the read loop drains the data and then gets the error from
+    // recv().
+    const chunk = Buffer.alloc(64 * 1024, "r");
+    expect(t.peer.write(chunk)).toBe(chunk.length);
     t.socket.resume();
     t.peer.terminate();
     await t.settled;
-    expect(t.events).toEqual(["error ECONNRESET", "close hadError=true"]);
     // Windows discards the receive queue on a reset. Linux and macOS keep it, and
     // like node, the data is delivered before the error.
-    if (!isWindows) expect(t.bytesRead()).toBeGreaterThan(0);
+    expect({ events: t.events, dataDelivered: t.bytesRead() > 0 }).toEqual({
+      events: ["error ECONNRESET", "close hadError=true"],
+      dataDelivered: !isWindows,
+    });
   });
 });