fix: improve internal proxied state signal heuristic (#11102)

Fixes #11069

.changeset/four-mice-hammer.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: improve internal proxied state signal heuristic

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

@@ -1,6 +1,11 @@
 import { DEV } from 'esm-env';
-import { get, batch_inspect, current_component_context, untrack } from './runtime.js';
-import { effect_active } from './reactivity/effects.js';
+import {
+	get,
+	batch_inspect,
+	current_component_context,
+	untrack,
+	current_effect
+} from './runtime.js';
 import {
 	array_prototype,
 	define_property,
@@ -206,7 +211,7 @@ const state_proxy_handler = {
 		// but only if it's an own property and not a prototype property
 		if (
 			s === undefined &&
-			(effect_active() || updating_derived) &&
+			(current_effect !== null || updating_derived) &&
 			(!(prop in target) || get_descriptor(target, prop)?.writable)
 		) {
 			s = (metadata.i ? source : mutable_source)(proxy(target[prop], metadata.i, metadata.o));
@@ -250,7 +255,10 @@ const state_proxy_handler = {
 		const has = Reflect.has(target, prop);
 
 		let s = metadata.s.get(prop);
-		if (s !== undefined || (effect_active() && (!has || get_descriptor(target, prop)?.writable))) {
+		if (
+			s !== undefined ||
+			(current_effect !== null && (!has || get_descriptor(target, prop)?.writable))
+		) {
 			if (s === undefined) {
 				s = (metadata.i ? source : mutable_source)(
 					has ? proxy(target[prop], metadata.i, metadata.o) : UNINITIALIZED
@@ -273,7 +281,7 @@ const state_proxy_handler = {
 		// we do so otherwise if we read it later, then the write won't be tracked and
 		// the heuristics of effects will be different vs if we had read the proxied
 		// object property before writing to that property.
-		if (s === undefined && effect_active()) {
+		if (s === undefined && current_effect !== null) {
 			// the read creates a signal
 			untrack(() => receiver[prop]);
 			s = metadata.s.get(prop);

packages/svelte/tests/runtime-runes/samples/proxied-state-property-access/Child.svelte

@@ -0,0 +1,5 @@
+<script>
+	const { settings } = $props();
+</script>
+
+Child: {settings.showInRgb}

packages/svelte/tests/runtime-runes/samples/proxied-state-property-access/_config.js

@@ -0,0 +1,22 @@
+import { flushSync } from '../../../../src/index-client';
+import { test } from '../../test';
+
+export default test({
+	html: `<button>click true</button> Child: true`,
+
+	async test({ assert, target }) {
+		const btn = target.querySelector('button');
+
+		flushSync(() => {
+			btn?.click();
+		});
+
+		assert.htmlEqual(target.innerHTML, `<button>click false</button> Child: false`);
+
+		flushSync(() => {
+			btn?.click();
+		});
+
+		assert.htmlEqual(target.innerHTML, `<button>click true</button> Child: true`);
+	}
+});

packages/svelte/tests/runtime-runes/samples/proxied-state-property-access/main.svelte

@@ -0,0 +1,19 @@
+<script context="module">
+	export const context = $state({
+		settings: {
+			showInRgb: true
+		}
+	})
+</script>
+
+<script>
+	import Child from './Child.svelte';
+
+	const { settings } = context
+</script>
+
+<button onclick={() => settings.showInRgb = !settings.showInRgb}>
+	click {settings.showInRgb}
+</button>
+
+<Child settings={settings} />