fix

Author: Rich-Harris

packages/svelte/src/internal/client/proxy.js

@@ -74,7 +74,7 @@ export function proxy(value, immutable = true, parent = null) {
 							? // @ts-expect-error
 								new Set([current_component_context.function])
 							: null
-						: parent.owners;
+						: new Set();
 			}
 
 			return proxy;

packages/svelte/tests/runtime-runes/samples/non-local-mutation-with-binding-3/Counter.svelte

@@ -0,0 +1,12 @@
+<script>
+	/** @type {{ shared: { count: number }, notshared: { count: number } }} */
+	let { shared = $bindable(), notshared } = $props();
+</script>
+
+<button onclick={() => shared.count += 1}>
+	clicks: {shared.count}
+</button>
+
+<button onclick={() => notshared.count += 1}>
+	clicks: {notshared.count}
+</button>

packages/svelte/tests/runtime-runes/samples/non-local-mutation-with-binding-3/_config.js

@@ -0,0 +1,53 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+/** @type {typeof console.warn} */
+let warn;
+
+/** @type {typeof console.trace} */
+let trace;
+
+/** @type {any[]} */
+let warnings = [];
+
+export default test({
+	html: `<button>clicks: 0</button><button>clicks: 0</button>`,
+
+	compileOptions: {
+		dev: true
+	},
+
+	before_test: () => {
+		warn = console.warn;
+		trace = console.trace;
+
+		console.warn = (...args) => {
+			warnings.push(...args);
+		};
+
+		console.trace = () => {};
+	},
+
+	after_test: () => {
+		console.warn = warn;
+		console.trace = trace;
+
+		warnings = [];
+	},
+
+	async test({ assert, target }) {
+		const [btn1, btn2] = target.querySelectorAll('button');
+
+		flushSync(() => btn1.click());
+		assert.htmlEqual(target.innerHTML, `<button>clicks: 1</button><button>clicks: 0</button>`);
+
+		assert.deepEqual(warnings, []);
+
+		flushSync(() => btn2.click());
+		assert.htmlEqual(target.innerHTML, `<button>clicks: 1</button><button>clicks: 1</button>`);
+
+		assert.deepEqual(warnings, [
+			'.../samples/non-local-mutation-with-binding-3/Counter.svelte mutated a value owned by .../samples/non-local-mutation-with-binding-3/main.svelte. This is strongly discouraged. Consider passing values to child components with `bind:`, or use a callback instead.'
+		]);
+	}
+});

packages/svelte/tests/runtime-runes/samples/non-local-mutation-with-binding-3/main.svelte

@@ -0,0 +1,13 @@
+<script>
+	import Counter from './Counter.svelte';
+
+	let object = $state({
+		shared: { count: 0 },
+		notshared: { count: 0 }
+	});
+</script>
+
+<Counter
+	bind:shared={object.shared}
+	notshared={object.notshared}
+/>