test(core): add GC-based tests for signal graph prevConsumer leak fix (#68681)

stewartmcgown · atscott · commit 2d809e317001 · 2026-06-04T19:25:36.000Z
Uses WeakRef + global.gc() to verify that destroyed effect consumers become garbage-collectable when a non-live computed reads the same producer. The jasmine_test target is configured with node_options: --expose-gc. GC tests are skipped in browser targets via isBrowser from @angular/private/testing. Made-with: Cursor PR Close #68681
diff --git a/packages/core/test/signals/BUILD.bazel b/packages/core/test/signals/BUILD.bazel
@@ -12,6 +12,7 @@ ts_project(
         "//packages/core",
         "//packages/core/primitives/signals",
         "//packages/core/src/util",
+        "//packages/private/testing",
     ],
 )
 
@@ -20,6 +21,7 @@ jasmine_test(
     data = [
         ":signals_lib",
     ],
+    node_options = ["--expose-gc"],
 )
 
 ng_web_test_suite(
diff --git a/packages/core/test/signals/signal_graph_leak_spec.ts b/packages/core/test/signals/signal_graph_leak_spec.ts
@@ -0,0 +1,68 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import {computed, signal, WritableSignal} from '../../src/core';
+import {createWatch, SIGNAL} from '../../primitives/signals';
+import {isBrowser, timeout} from '@angular/private/testing';
+
+describe('signal graph: destroyed consumers should be GC-eligible', () => {
+  if (isBrowser) {
+    it('should pass', () => {});
+    return;
+  }
+
+  function setupAndReturnRef(source: WritableSignal<number>): WeakRef<object> {
+    const watch = createWatch(
+      () => source(),
+      () => {},
+      true,
+    );
+    watch.run();
+
+    const ref = new WeakRef(watch[SIGNAL]);
+
+    // Non-live computed that also reads source.
+    const derived = computed(() => source() + 1);
+    derived();
+
+    // Clearing the graph edges.
+    watch.destroy();
+
+    return ref;
+  }
+
+  it('should GC a destroyed effect when a non-live computed reads the same producer', async () => {
+    const source = signal(0);
+    const ref = setupAndReturnRef(source);
+
+    (globalThis as any).gc();
+    await timeout();
+    (globalThis as any).gc();
+
+    expect(ref.deref()).toBeUndefined();
+  });
+
+  it('should GC destroyed effects across repeated create/destroy cycles', async () => {
+    const source = signal(0);
+    const derived = computed(() => source() + 1);
+    derived();
+
+    const refs: WeakRef<object>[] = [];
+    for (let i = 0; i < 5; i++) {
+      refs.push(setupAndReturnRef(source));
+    }
+
+    (globalThis as any).gc();
+    await timeout();
+    (globalThis as any).gc();
+
+    for (let i = 0; i < refs.length; i++) {
+      expect(refs[i].deref()).withContext(`cycle ${i}`).toBeUndefined();
+    }
+  });
+});

Original file line number	Diff line number	Diff line change
`@@ -12,6 +12,7 @@ ts_project(`
`12`	`12`	`"//packages/core",`
`13`	`13`	`"//packages/core/primitives/signals",`
`14`	`14`	`"//packages/core/src/util",`
	`15`	`+ "//packages/private/testing",`
`15`	`16`	`],`
`16`	`17`	`)`
`17`	`18`
`@@ -20,6 +21,7 @@ jasmine_test(`
`20`	`21`	`data = [`
`21`	`22`	`":signals_lib",`
`22`	`23`	`],`
	`24`	`+ node_options = ["--expose-gc"],`
`23`	`25`	`)`
`24`	`26`
`25`	`27`	`ng_web_test_suite(`