Merge 12a6051884 into 5895c637b0

.changeset/twenty-bears-fly.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: enhance snapshot type handling for array structures in $state.snapshot

packages/svelte/src/ambient.d.ts

@@ -86,7 +86,13 @@ declare namespace $state {
 			: T extends { toJSON(): infer R }
 				? R
 				: T extends readonly unknown[]
-					? { [K in keyof T]: Snapshot<T[K]> }
+					? number extends T['length']
+						? T extends Array<infer U>
+							? Array<Snapshot<U>>
+							: T extends ReadonlyArray<infer U>
+								? ReadonlyArray<Snapshot<U>>
+								: never
+						: { [K in keyof T]: Snapshot<T[K]> }
 					: T extends Array<infer U>
 						? Array<Snapshot<U>>
 						: T extends object

packages/svelte/tests/types/state.ts

@@ -0,0 +1,15 @@
+import type { ClassValue } from 'clsx';
+
+// Regression test for #17117: this should not trigger deep/infinite type instantiation
+const cls = $state.raw<ClassValue[]>([]);
+const cls_snap: ReturnType<typeof $state.snapshot<ClassValue[]>> =
+	$state.snapshot<ClassValue[]>(cls);
+
+type SnapshotTuple = ReturnType<typeof $state.snapshot<[number, string]>>;
+
+const tuple_ok: SnapshotTuple = [1, 'a'];
+tuple_ok[0] === 1;
+tuple_ok[1] === 'a';
+
+// @ts-expect-error tuple element type should be preserved
+const tuple_wrong: SnapshotTuple = [1, 2];

packages/svelte/types/index.d.ts

@@ -3404,7 +3404,13 @@ declare namespace $state {
 			: T extends { toJSON(): infer R }
 				? R
 				: T extends readonly unknown[]
-					? { [K in keyof T]: Snapshot<T[K]> }
+					? number extends T['length']
+						? T extends Array<infer U>
+							? Array<Snapshot<U>>
+							: T extends ReadonlyArray<infer U>
+								? ReadonlyArray<Snapshot<U>>
+								: never
+						: { [K in keyof T]: Snapshot<T[K]> }
 					: T extends Array<infer U>
 						? Array<Snapshot<U>>
 						: T extends object