Fix regression with IPC (#16465)

src/bun.js/ipc.zig

@@ -339,7 +339,7 @@ const SocketIPCData = struct {
         const bytes = getVersionPacket(this.mode);
         if (bytes.len > 0) {
             const n = this.socket.write(bytes, false);
-            if (n != bytes.len) {
+            if (n >= 0 and n < @as(i32, @intCast(bytes.len))) {
                 this.outgoing.write(bytes[@intCast(n)..]) catch bun.outOfMemory();
             }
         }

src/bun.js/node/node_cluster_binding.zig

@@ -1,3 +1,8 @@
+// Most of this code should be rewritten.
+// - Usage of JSC.Strong here is likely to cause memory leaks.
+// - These sequence numbers and ACKs shouldn't exist from JavaScript's perspective
+//   at all. It should happen in the protocol before it reaches JS.
+// - We should not be creating JSFunction's in process.nextTick.
 const std = @import("std");
 const bun = @import("root").bun;
 const Environment = bun.Environment;
@@ -35,6 +40,8 @@ pub fn sendHelperChild(globalThis: *JSC.JSGlobalObject, callframe: *JSC.CallFram
         return globalThis.throwInvalidArgumentTypeValue("message", "object", message);
     }
     if (callback.isFunction()) {
+        // TODO: remove this strong. This is expensive and would be an easy way to create a memory leak.
+        // These sequence numbers shouldn't exist from JavaScript's perspective at all.
         child_singleton.callbacks.put(bun.default_allocator, child_singleton.seq, JSC.Strong.create(callback, globalThis)) catch bun.outOfMemory();
     }
 
@@ -52,7 +59,7 @@ pub fn sendHelperChild(globalThis: *JSC.JSGlobalObject, callframe: *JSC.CallFram
         fn impl(globalThis_: *JSC.JSGlobalObject, callframe_: *JSC.CallFrame) bun.JSError!JSC.JSValue {
             const arguments_ = callframe_.arguments_old(1).slice();
             const ex = arguments_[0];
-            Process__emitErrorEvent(globalThis_, ex);
+            Process__emitErrorEvent(globalThis_, ex.toError() orelse ex);
             return .undefined;
         }
     };
@@ -73,6 +80,7 @@ pub fn sendHelperChild(globalThis: *JSC.JSGlobalObject, callframe: *JSC.CallFram
 pub fn onInternalMessageChild(globalThis: *JSC.JSGlobalObject, callframe: *JSC.CallFrame) bun.JSError!JSC.JSValue {
     log("onInternalMessageChild", .{});
     const arguments = callframe.arguments_old(2).ptr;
+    // TODO: we should not create two JSC.Strong here. If absolutely necessary, a single Array. should be all we use.
     child_singleton.worker = JSC.Strong.create(arguments[0], globalThis);
     child_singleton.cb = JSC.Strong.create(arguments[1], globalThis);
     try child_singleton.flush(globalThis);
@@ -85,17 +93,16 @@ pub fn handleInternalMessageChild(globalThis: *JSC.JSGlobalObject, message: JSC.
     try child_singleton.dispatch(message, globalThis);
 }
 
-//
-//
-//
-
+// TODO: rewrite this code.
 /// Queue for messages sent between parent and child processes in an IPC environment. node:cluster sends json serialized messages
 /// to describe different events it performs. It will send a message with an incrementing sequence number and then call a callback
 /// when a message is recieved with an 'ack' property of the same sequence number.
 pub const InternalMsgHolder = struct {
     seq: i32 = 0,
-    callbacks: std.AutoArrayHashMapUnmanaged(i32, JSC.Strong) = .{},
 
+    // TODO: move this to an Array or a JS Object or something which doesn't
+    // individually create a Strong for every single IPC message...
+    callbacks: std.AutoArrayHashMapUnmanaged(i32, JSC.Strong) = .{},
     worker: JSC.Strong = .{},
     cb: JSC.Strong = .{},
     messages: std.ArrayListUnmanaged(JSC.Strong) = .{},
@@ -211,6 +218,7 @@ pub fn onInternalMessagePrimary(globalThis: *JSC.JSGlobalObject, callframe: *JSC
     const arguments = callframe.arguments_old(3).ptr;
     const subprocess = arguments[0].as(bun.JSC.Subprocess).?;
     const ipc_data = subprocess.ipc() orelse return .undefined;
+    // TODO: remove these strongs.
     ipc_data.internal_msg_queue.worker = JSC.Strong.create(arguments[1], globalThis);
     ipc_data.internal_msg_queue.cb = JSC.Strong.create(arguments[2], globalThis);
     return .undefined;
@@ -221,6 +229,7 @@ pub fn handleInternalMessagePrimary(globalThis: *JSC.JSGlobalObject, subprocess:
 
     const event_loop = globalThis.bunVM().eventLoop();
 
+    // TODO: investigate if "ack" and "seq" are observable and if they're not, remove them entirely.
     if (try message.get(globalThis, "ack")) |p| {
         if (!p.isUndefined()) {
             const ack = p.toInt32();