fix

Author: Rich-Harris

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

@@ -403,16 +403,8 @@ export function client_component(analysis, options) {
 	// so that it can effectively clean up the store subscription even after the user effects runs
 	if (should_inject_context) {
 		if (analysis.needs_mutation_validation) {
-			// It's easier to have the mutation validator instance be on the module level because of hoisted events
-			state.hoisted.push(b.let('$$ownership_validator'));
 			component_block.body.unshift(
-				b.stmt(
-					b.assignment(
-						'=',
-						b.id('$$ownership_validator'),
-						b.call('$.create_ownership_validator', b.id('$$props'))
-					)
-				)
+				b.var('$$ownership_validator', b.call('$.create_ownership_validator', b.id('$$props')))
 			);
 		}
 

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

@@ -1,10 +1,10 @@
-/** @import { ArrowFunctionExpression, Expression, FunctionDeclaration, FunctionExpression, Identifier, Pattern, PrivateIdentifier, Statement } from 'estree' */
-/** @import { AST, Binding } from '#compiler' */
+/** @import { ArrowFunctionExpression, AssignmentExpression, Expression, FunctionDeclaration, FunctionExpression, Identifier, Node, Pattern, UpdateExpression } from 'estree' */
+/** @import { Binding } from '#compiler' */
 /** @import { ClientTransformState, ComponentClientTransformState, ComponentContext } from './types.js' */
 /** @import { Analysis } from '../../types.js' */
 /** @import { Scope } from '../../scope.js' */
 import * as b from '../../../utils/builders.js';
-import { extract_identifiers, is_simple_expression } from '../../../utils/ast.js';
+import { is_simple_expression } from '../../../utils/ast.js';
 import {
 	PROPS_IS_LAZY_INITIAL,
 	PROPS_IS_IMMUTABLE,
@@ -13,7 +13,8 @@ import {
 	PROPS_IS_BINDABLE
 } from '../../../../constants.js';
 import { dev } from '../../../state.js';
-import { get_value } from './visitors/shared/declarations.js';
+import { walk } from 'zimmerframe';
+import { validate_mutation } from './visitors/shared/utils.js';
 
 /**
  * @param {Binding} binding
@@ -110,6 +111,30 @@ function get_hoisted_params(node, context) {
 			}
 		}
 	}
+
+	if (dev) {
+		// this is a little hacky, but necessary for ownership validation
+		// to work inside hoisted event handlers
+
+		/**
+		 * @param {AssignmentExpression | UpdateExpression} node
+		 * @param {{ next: () => void, stop: () => void }} context
+		 */
+		function visit(node, { next, stop }) {
+			if (validate_mutation(node, /** @type {any} */ (context), node) !== node) {
+				params.push(b.id('$$ownership_validator'));
+				stop();
+			} else {
+				next();
+			}
+		}
+
+		walk(/** @type {Node} */ (node), null, {
+			AssignmentExpression: visit,
+			UpdateExpression: visit
+		});
+	}
+
 	return params;
 }