From ddb968cc35abe03b511bee0bab4cca978166b48d Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Tue, 20 Feb 2024 16:55:36 -0500
Subject: [PATCH] fix: ensure proxy owner set always has 1 or more members
 (#10577)

* fix missing owners

* regression test

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/sour-bags-fail.md                  |  5 +++
 packages/svelte/src/internal/client/proxy.js  |  2 +-
 .../_config.js                                | 37 +++++++++++++++++++
 .../main.svelte                               |  9 +++++
 .../state.svelte.js                           |  1 +
 5 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/sour-bags-fail.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/state.svelte.js

diff --git a/.changeset/sour-bags-fail.md b/.changeset/sour-bags-fail.md
new file mode 100644
index 0000000000..67c9c43a34
--- /dev/null
+++ b/.changeset/sour-bags-fail.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: inherit ownerlessness when creating child proxies
diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index e17edc248d..8f26e67806 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -84,7 +84,7 @@ export function proxy(value, immutable = true, owners) {
 							? // @ts-expect-error
 								new Set([current_component_context.function])
 							: null
-						: new Set(owners);
+						: owners && new Set(owners);
 			}
 
 			return proxy;
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/_config.js b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/_config.js
new file mode 100644
index 0000000000..dc600e1461
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/_config.js
@@ -0,0 +1,37 @@
+import { test } from '../../test';
+
+/** @type {typeof console.warn} */
+let warn;
+
+/** @type {any[]} */
+let warnings = [];
+
+export default test({
+	html: `<button>clicks: 0</button>`,
+
+	compileOptions: {
+		dev: true
+	},
+
+	before_test: () => {
+		warn = console.warn;
+
+		console.warn = (...args) => {
+			warnings.push(...args);
+		};
+	},
+
+	after_test: () => {
+		console.warn = warn;
+		warnings = [];
+	},
+
+	async test({ assert, target }) {
+		const btn = target.querySelector('button');
+		await btn?.click();
+
+		assert.htmlEqual(target.innerHTML, `<button>clicks: 1</button>`);
+
+		assert.deepEqual(warnings, []);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/main.svelte
new file mode 100644
index 0000000000..ad450a937e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	import { global } from './state.svelte.js';
+
+	global.a = { b: 0 };
+</script>
+
+<button onclick={() => global.a.b += 1}>
+	clicks: {global.a.b}
+</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/state.svelte.js b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/state.svelte.js
new file mode 100644
index 0000000000..3e7a68cf97
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-inherited-owner-2/state.svelte.js
@@ -0,0 +1 @@
+export let global = $state({});