fix: loosen proxy signal creation heuristics (#11109)

* fix: loosen proxy signal creation heuristics

* tighten up test

* update comment

* no need to create a source outside an effect here, because it can't result in a reference

* preserve reference to props.$$events

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/early-months-whisper.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: loosen proxy signal creation heuristics

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

@@ -19,7 +19,6 @@ import {
 import { add_owner, check_ownership, strip_owner } from './dev/ownership.js';
 import { mutable_source, source, set } from './reactivity/sources.js';
 import { STATE_SYMBOL } from './constants.js';
-import { updating_derived } from './reactivity/deriveds.js';
 import { UNINITIALIZED } from '../../constants.js';
 
 /**
@@ -207,13 +206,8 @@ const state_proxy_handler = {
 		const metadata = target[STATE_SYMBOL];
 		let s = metadata.s.get(prop);
 
-		// if we're reading a property in a reactive context, create a source,
-		// but only if it's an own property and not a prototype property
-		if (
-			s === undefined &&
-			(current_effect !== null || updating_derived) &&
-			(!(prop in target) || get_descriptor(target, prop)?.writable)
-		) {
+		// create a source, but only if it's an own property and not a prototype property
+		if (s === undefined && (!(prop in target) || get_descriptor(target, prop)?.writable)) {
 			s = (metadata.i ? source : mutable_source)(proxy(target[prop], metadata.i, metadata.o));
 			metadata.s.set(prop, s);
 		}
@@ -281,7 +275,7 @@ 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 && current_effect !== null) {
+		if (s === undefined) {
 			// the read creates a signal
 			untrack(() => receiver[prop]);
 			s = metadata.s.get(prop);

packages/svelte/src/legacy/legacy-client.js

@@ -53,7 +53,7 @@ export function asClassComponent(component) {
 
 class Svelte4Component {
 	/** @type {any} */
-	#events = {};
+	#events;
 
 	/** @type {Record<string, any>} */
 	#instance;
@@ -70,7 +70,7 @@ class Svelte4Component {
 		// Using proxy state here isn't completely mirroring the Svelte 4 behavior, because mutations to a property
 		// cause fine-grained updates to only the places where that property is used, and not the entire property.
 		// Reactive statements and actions (the things where this matters) are handling this properly regardless, so it should be fine in practise.
-		const props = proxy({ ...(options.props || {}), $$events: this.#events }, false);
+		const props = proxy({ ...(options.props || {}), $$events: {} }, false);
 		this.#instance = (options.hydrate ? hydrate : mount)(options.component, {
 			target: options.target,
 			props,
@@ -79,6 +79,8 @@ class Svelte4Component {
 			recover: options.recover
 		});
 
+		this.#events = props.$$events;
+
 		for (const key of Object.keys(this.#instance)) {
 			if (key === '$set' || key === '$destroy' || key === '$on') continue;
 			define_property(this, key, {

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

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

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

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