fix: use strategy suggested by actually competent person aka @dummdidumm

Author: paoloricciuti

packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js

@@ -348,7 +348,6 @@ export function validate_mutation(node, context, expression) {
 		b.literal(binding.prop_alias),
 		b.array(path),
 		expression,
-		binding.prop_alias != null && b.id(binding.prop_alias),
 		loc && b.literal(loc.line),
 		loc && b.literal(loc.column)
 	);

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

@@ -23,6 +23,5 @@ export const EFFECT_HAS_DERIVED = 1 << 20;
 export const EFFECT_IS_UPDATING = 1 << 21;
 
 export const STATE_SYMBOL = Symbol('$state');
-export const BINDABLE_FALLBACK_SYMBOL = Symbol('bindable fallback');
 export const LEGACY_PROPS = Symbol('legacy props');
 export const LOADING_ATTR_SYMBOL = Symbol('');

packages/svelte/src/internal/client/dev/ownership.js

@@ -1,7 +1,7 @@
 /** @typedef {{ file: string, line: number, column: number }} Location */
 
 import { get_descriptor } from '../../shared/utils.js';
-import { BINDABLE_FALLBACK_SYMBOL, LEGACY_PROPS, STATE_SYMBOL } from '../constants.js';
+import { LEGACY_PROPS, STATE_SYMBOL } from '../constants.js';
 import { FILENAME } from '../../../constants.js';
 import { component_context } from '../context.js';
 import * as w from '../warnings.js';
@@ -22,13 +22,12 @@ export function create_ownership_validator(props) {
 		 * @param {string} prop
 		 * @param {any[]} path
 		 * @param {any} result
-		 * @param {any} prop_value
 		 * @param {number} line
 		 * @param {number} column
 		 */
-		mutation: (prop, path, result, prop_value, line, column) => {
+		mutation: (prop, path, result, line, column) => {
 			const name = path[0];
-			if (is_bound(props, name) || !parent || prop_value()?.[BINDABLE_FALLBACK_SYMBOL]) {
+			if (is_bound(props, name) || !parent) {
 				return result;
 			}
 
@@ -53,14 +52,7 @@ export function create_ownership_validator(props) {
 		 * @param {() => any} value
 		 */
 		binding: (key, child_component, value) => {
-			var val;
-			if (
-				!is_bound(props, key) &&
-				parent &&
-				// we do this trick to prevent calling the value function twice
-				(val = value())?.[STATE_SYMBOL] &&
-				!val[BINDABLE_FALLBACK_SYMBOL]
-			) {
+			if (!is_bound(props, key) && parent && value()?.[STATE_SYMBOL]) {
 				w.ownership_invalid_binding(
 					component[FILENAME],
 					key,
@@ -80,5 +72,9 @@ function is_bound(props, prop_name) {
 	// Can be the case when someone does `mount(Component, props)` with `let props = $state({...})`
 	// or `createClassComponent(Component, props)`
 	const is_entry_props = STATE_SYMBOL in props || LEGACY_PROPS in props;
-	return !!get_descriptor(props, prop_name)?.set || (is_entry_props && prop_name in props);
+	return (
+		!!get_descriptor(props, prop_name)?.set ||
+		(is_entry_props && prop_name in props) ||
+		!(prop_name in props)
+	);
 }

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

@@ -9,7 +9,7 @@ import {
 	object_prototype
 } from '../shared/utils.js';
 import { state as source, set } from './reactivity/sources.js';
-import { BINDABLE_FALLBACK_SYMBOL, STATE_SYMBOL } from './constants.js';
+import { STATE_SYMBOL } from './constants.js';
 import { UNINITIALIZED } from '../../constants.js';
 import * as e from './errors.js';
 import { get_stack } from './dev/tracing.js';
@@ -63,12 +63,6 @@ export function proxy(value) {
 
 	return new Proxy(/** @type {any} */ (value), {
 		defineProperty(_, prop, descriptor) {
-			// we allow non enumerable/writable defines if the prop being set is our own symbol
-			// this should be fine for the invariants since the user can't get a handle to the symbol
-			if (DEV && prop === BINDABLE_FALLBACK_SYMBOL) {
-				return Reflect.defineProperty(_, prop, descriptor);
-			}
-
 			if (
 				!('value' in descriptor) ||
 				descriptor.configurable === false ||
@@ -129,9 +123,6 @@ export function proxy(value) {
 			if (prop === STATE_SYMBOL) {
 				return value;
 			}
-			if (DEV && prop === BINDABLE_FALLBACK_SYMBOL) {
-				return Reflect.get(target, prop);
-			}
 
 			var s = sources.get(prop);
 			var exists = prop in target;
@@ -272,9 +263,7 @@ export function proxy(value) {
 
 			var own_keys = Reflect.ownKeys(target).filter((key) => {
 				var source = sources.get(key);
-				return (
-					source === undefined || source.v !== UNINITIALIZED || key !== BINDABLE_FALLBACK_SYMBOL
-				);
+				return source === undefined || source.v !== UNINITIALIZED;
 			});
 
 			for (var [key, source] of sources) {

packages/svelte/src/internal/client/reactivity/props.js

@@ -13,12 +13,7 @@ import { derived, derived_safe_equal } from './deriveds.js';
 import { get, captured_signals, untrack } from '../runtime.js';
 import { safe_equals } from './equality.js';
 import * as e from '../errors.js';
-import {
-	BINDABLE_FALLBACK_SYMBOL,
-	LEGACY_DERIVED_PROP,
-	LEGACY_PROPS,
-	STATE_SYMBOL
-} from '../constants.js';
+import { LEGACY_DERIVED_PROP, LEGACY_PROPS, STATE_SYMBOL } from '../constants.js';
 import { proxy } from '../proxy.js';
 import { capture_store_binding } from './store.js';
 import { legacy_mode_flag } from '../../flags/index.js';
@@ -309,29 +304,6 @@ export function prop(props, key, flags, fallback) {
 		if (setter) setter(prop_value);
 	}
 
-	/**
-	 * @param {any} value
-	 */
-	function set_bindable_fallback(value) {
-		if (DEV && !setter && fallback_used && value != null && typeof value === 'object') {
-			// in dev we issue a warning if a bindable prop is passed with bindable
-			// to a child if the prop doesn't have a setter but if it's a fallback
-			// it's a false positive since the state it's actually created in this
-			// component so we store the fact that this is a bindable fallback with
-			// a symbol
-			define_property(value, BINDABLE_FALLBACK_SYMBOL, {
-				enumerable: false,
-				// it needs to be configurable or the proxy will complain when we return true
-				// for a non configurable property
-				configurable: true,
-				writable: false,
-				value: true
-			});
-		}
-	}
-
-	set_bindable_fallback(prop_value);
-
 	/** @type {() => V} */
 	var getter;
 	if (runes) {
@@ -427,11 +399,6 @@ export function prop(props, key, flags, fallback) {
 		if (arguments.length > 0) {
 			const new_value = mutation ? get(current_value) : runes && bindable ? proxy(value) : value;
 
-			// we only care to add the symbol if the original prop is reassigned
-			if (runes && bindable && !mutation) {
-				set_bindable_fallback(new_value);
-			}
-
 			if (!current_value.equals(new_value)) {
 				from_child = true;
 				set(inner_current_value, new_value);