fix: preserve zero snapshot array length overrides

Co-authored-by: Mathieu Decaffmeyer <5883963+mathieuprog@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: 3 people

.changeset/fix-snapshot-array-length-zero.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/signals": patch
+---
+
+Preserve snapshot array length overrides when the overridden length is 0.

packages/solid-signals/src/store/utils.ts

@@ -44,7 +44,7 @@ function snapshotImpl<T>(
     map.set(item, item);
   }
   if (isArray) {
-    const len = override?.length || item.length;
+    const len = override?.length ?? item.length;
     for (let i = 0; i < len; i++) {
       v = override && i in override ? override[i] : item[i];
       if (v === $DELETED) continue;

packages/solid-signals/tests/snapshot.test.ts

@@ -10,7 +10,8 @@ import {
   getOwner,
   markSnapshotScope,
   releaseSnapshotScope,
-  setSnapshotCapture
+  setSnapshotCapture,
+  snapshot
 } from "../src/index.js";
 
 afterEach(() => {
@@ -469,6 +470,14 @@ describe("store snapshot support", () => {
     expect($age()).toBe(30);
     clearSnapshots();
   });
+
+  it("preserves an overridden array length of 0", () => {
+    const [store, setStore] = createStore<number[]>([1, 2, 3]);
+
+    setStore(() => []);
+
+    expect(snapshot(store)).toEqual([]);
+  });
 });
 
 describe("pending projection skips snapshot capture", () => {