From bffab530ecb8a0e86dbb0f4a98cb6e7691e409b2 Mon Sep 17 00:00:00 2001
From: Boris Petrov <boris_petrov@live.com>
Date: Tue, 5 Aug 2025 19:08:02 +0300
Subject: [PATCH] Allow for tracked-array subtypes

---
 packages/@glimmer/validator/index.ts               |  2 +-
 .../@glimmer/validator/lib/collections/array.ts    |  4 +++-
 .../validator/test/collections/array-test.ts       | 14 +++++++++++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/packages/@glimmer/validator/index.ts b/packages/@glimmer/validator/index.ts
index a3abcaa50..e7325033b 100644
--- a/packages/@glimmer/validator/index.ts
+++ b/packages/@glimmer/validator/index.ts
@@ -8,7 +8,7 @@ if (Reflect.has(globalThis, GLIMMER_VALIDATOR_REGISTRATION)) {
 
 Reflect.set(globalThis, GLIMMER_VALIDATOR_REGISTRATION, true);
 
-export { trackedArray } from './lib/collections/array';
+export { TrackedArray, trackedArray } from './lib/collections/array';
 export { trackedMap } from './lib/collections/map';
 export { trackedObject } from './lib/collections/object';
 export { trackedSet } from './lib/collections/set';
diff --git a/packages/@glimmer/validator/lib/collections/array.ts b/packages/@glimmer/validator/lib/collections/array.ts
index e58905858..6bbb6c0ee 100644
--- a/packages/@glimmer/validator/lib/collections/array.ts
+++ b/packages/@glimmer/validator/lib/collections/array.ts
@@ -147,7 +147,7 @@ class TrackedArray<T = unknown> {
       },
 
       getPrototypeOf() {
-        return TrackedArray.prototype;
+        return Object.getPrototypeOf(self);
       },
     }) as TrackedArray<T>;
   }
@@ -197,6 +197,8 @@ interface TrackedArray<T = unknown> extends Array<T> {}
 // Ensure instanceof works correctly
 Object.setPrototypeOf(TrackedArray.prototype, Array.prototype);
 
+export { TrackedArray };
+
 export function trackedArray<T = unknown>(
   data?: T[],
   options?: { equals?: (a: T, b: T) => boolean; description?: string }
diff --git a/packages/@glimmer/validator/test/collections/array-test.ts b/packages/@glimmer/validator/test/collections/array-test.ts
index 0a5d1e985..a87ca01aa 100644
--- a/packages/@glimmer/validator/test/collections/array-test.ts
+++ b/packages/@glimmer/validator/test/collections/array-test.ts
@@ -1,6 +1,6 @@
 /* eslint-disable import-x/no-extraneous-dependencies */
 
-import { trackedArray } from '@glimmer/validator';
+import { TrackedArray, trackedArray } from '@glimmer/validator';
 import { expectTypeOf } from 'expect-type';
 
 import { module, test } from '../-utils';
@@ -42,6 +42,18 @@ module('@glimmer/validator: trackedArray()', () => {
     assert.strictEqual(arr[0], undefined);
   });
 
+  test('Allows creating subtypes', (assert) => {
+    class MyTrackedArray extends TrackedArray {
+      constructor() {
+        super([], { equals: Object.is, description: undefined });
+      }
+    }
+
+    let arr = new MyTrackedArray();
+
+    assert.strictEqual(Object.getPrototypeOf(arr).constructor, MyTrackedArray);
+  });
+
   module('methods', () => {
     test('isArray', (assert) => {
       let arr = trackedArray();