src: use uv_async_t for WeakRefs

Schedule a task on the main event loop, similar to what the HTML
spec recommends for browsers.

Alternative to https://github.com/nodejs/node/pull/30198

PR-URL: https://github.com/nodejs/node/pull/30616
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

2 files changed, 29 insertions, 0 deletions

diff --git a/test/parallel/test-finalization-group-error.js b/test/parallel/test-finalization-group-error.js
index 0754370f2d..0685811f55 100644
--- a/test/parallel/test-finalization-group-error.js
+++ b/test/parallel/test-finalization-group-error.js
@@ -18,6 +18,10 @@ setTimeout(() => {
     name: 'Error',
     message: 'test',
   });
+
+  // Give the callbacks scheduled by global.gc() time to run, as the underlying
+  // uv_async_t is unref’ed.
+  setTimeout(() => {}, 200);
 }, 200);
 
 process.on('uncaughtException', common.mustCall());
diff --git a/test/parallel/test-finalization-group-regular-gc.js b/test/parallel/test-finalization-group-regular-gc.js
new file mode 100644
index 0000000000..7a4a4797ea
--- /dev/null
+++ b/test/parallel/test-finalization-group-regular-gc.js
@@ -0,0 +1,25 @@
+// Flags: --harmony-weak-refs
+'use strict';
+require('../common');
+const assert = require('assert');
+
+// Test that finalization callbacks do not crash when caused through a regular
+// GC (not global.gc()).
+
+const start = Date.now();
+const g = new globalThis.FinalizationGroup(() => {
+  const diff = Date.now() - start;
+  assert(diff < 10000, `${diff} >= 10000`);
+});
+g.register({}, 42);
+
+setImmediate(() => {
+  const arr = [];
+  // Build up enough memory usage to hopefully trigger a platform task but not
+  // enough to trigger GC as an interrupt.
+  while (arr.length < 1000000) arr.push([]);
+
+  setTimeout(() => {
+    g;  // Keep reference alive.
+  }, 200000).unref();
+});