shallow copy state when freezing

Author: Rich-Harris

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

@@ -0,0 +1,40 @@
+import { DEV } from 'esm-env';
+import { define_property, is_array, is_frozen, object_freeze } from '../shared/utils.js';
+import { STATE_FROZEN_SYMBOL, STATE_SYMBOL } from './constants.js';
+
+/**
+ * Expects a value that was wrapped with `freeze` and makes it frozen in DEV.
+ * @template T
+ * @param {T} value
+ * @returns {Readonly<T>}
+ */
+export function freeze(value) {
+	if (
+		typeof value === 'object' &&
+		value !== null &&
+		!is_frozen(value) &&
+		!(STATE_FROZEN_SYMBOL in value)
+	) {
+		var copy = /** @type {T} */ (value);
+
+		// If the object is already proxified, then clone the value
+		if (STATE_SYMBOL in value) {
+			copy = /** @type {T} */ (is_array(value) ? [...value] : { ...value });
+		}
+
+		define_property(copy, STATE_FROZEN_SYMBOL, {
+			value: true,
+			writable: true,
+			enumerable: false
+		});
+
+		// Freeze the object in DEV
+		if (DEV) {
+			object_freeze(copy);
+		}
+
+		return /** @type {Readonly<T>} */ (copy);
+	}
+
+	return value;
+}

packages/svelte/src/internal/client/freeze.test.ts

@@ -0,0 +1,19 @@
+import { freeze } from './freeze.js';
+import { assert, test } from 'vitest';
+import { proxy } from './proxy.js';
+
+test('freezes an object', () => {
+	const frozen = freeze({ a: 1 });
+
+	assert.throws(() => {
+		// @ts-expect-error
+		frozen.a += 1;
+	}, /Cannot assign to read only property/);
+});
+
+test('preserves classes', () => {
+	class Foo {}
+	const frozen = freeze(proxy([new Foo()]));
+
+	assert.ok(frozen[0] instanceof Foo);
+});

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

@@ -91,6 +91,7 @@ export {
 	template_with_script,
 	text
 } from './dom/template.js';
+export { freeze } from './freeze.js';
 export { derived, derived_safe_equal } from './reactivity/deriveds.js';
 export {
 	effect_tracking,
@@ -136,7 +137,6 @@ export {
 	pop,
 	push,
 	unwrap,
-	freeze,
 	deep_read,
 	deep_read_state,
 	getAllContexts,

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

@@ -1,12 +1,5 @@
 import { DEV } from 'esm-env';
-import {
-	define_property,
-	get_descriptors,
-	get_prototype_of,
-	is_frozen,
-	object_freeze
-} from '../shared/utils.js';
-import { snapshot } from '../shared/clone.js';
+import { define_property, get_descriptors, get_prototype_of } from '../shared/utils.js';
 import {
 	destroy_effect,
 	effect,
@@ -28,8 +21,7 @@ import {
 	BLOCK_EFFECT,
 	ROOT_EFFECT,
 	LEGACY_DERIVED_PROP,
-	DISCONNECTED,
-	STATE_FROZEN_SYMBOL
+	DISCONNECTED
 } from './constants.js';
 import { flush_tasks } from './dom/task.js';
 import { add_owner } from './dev/ownership.js';
@@ -1211,36 +1203,3 @@ if (DEV) {
 	throw_rune_error('$props');
 	throw_rune_error('$bindable');
 }
-
-/**
- * Expects a value that was wrapped with `freeze` and makes it frozen in DEV.
- * @template T
- * @param {T} value
- * @returns {Readonly<T>}
- */
-export function freeze(value) {
-	if (
-		typeof value === 'object' &&
-		value != null &&
-		!is_frozen(value) &&
-		!(STATE_FROZEN_SYMBOL in value)
-	) {
-		// If the object is already proxified, then snapshot the value
-		var copy = STATE_SYMBOL in value ? snapshot(value) : value;
-
-		define_property(copy, STATE_FROZEN_SYMBOL, {
-			value: true,
-			writable: true,
-			enumerable: false
-		});
-
-		// Freeze the object in DEV
-		if (DEV) {
-			object_freeze(copy);
-		}
-
-		return /** @type {Readonly<T>} */ (copy);
-	}
-
-	return value;
-}