fix: prevent createDeferred from keeping Node.js process alive (#2588)

* fix: prevent createDeferred from keeping Node.js process alive

The scheduler uses MessageChannel internally for task scheduling.
In Node.js (with -C browser flag), active MessagePort listeners
keep the event loop alive even after all work is done and dispose()
has been called. This causes the process to hang indefinitely.

The fix calls unref() on both MessageChannel ports so they don't
prevent natural process exit. The unref method is Node.js-specific
and doesn't exist in browsers, so we guard the call with a typeof
check.

Fixes #2570

* add changeset for createDeferred node hang fix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: veeceey

.changeset/cyan-comics-worry.md

@@ -0,0 +1,5 @@
+---
+"solid-js": patch
+---
+
+fix: prevent createDeferred from keeping Node.js process alive

packages/solid/src/reactive/scheduler.ts

@@ -29,6 +29,12 @@ const maxSigned31BitInt = 1073741823;
 function setupScheduler() {
   const channel = new MessageChannel(),
     port = channel.port2;
+  // In Node.js, active MessagePort listeners keep the event loop alive.
+  // Calling unref() allows the process to exit naturally when there is no
+  // other work keeping it alive (e.g. after dispose). unref is not available
+  // in browsers, so we guard the call.
+  if (typeof channel.port1.unref === "function") channel.port1.unref();
+  if (typeof port.unref === "function") port.unref();
   scheduleCallback = () => port.postMessage(null);
   channel.port1.onmessage = () => {
     if (scheduledCallback !== null) {