fix: don't hoist function when already referenced in module scope

fixes #10279

Author: dummdidumm

.changeset/many-trees-fix.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: don't hoist function when already referenced in module scope

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -94,6 +94,11 @@ function get_delegated_event(event_name, handler, context) {
 	} else if (handler.type === 'Identifier') {
 		binding = context.state.scope.get(handler.name);
 
+		if (context.state.analysis.module.scope.references.has(handler.name)) {
+			// If a binding with the same name is referenced in the module scope (even if not declared there), bail-out
+			return non_hoistable;
+		}
+
 		if (binding != null) {
 			for (const { path } of binding.references) {
 				const parent = path.at(-1);

packages/svelte/tests/runtime-runes/samples/event-attribute-not-hoistable/_config.js

@@ -1,18 +1,25 @@
 import { test } from '../../test';
 
-// Checks that event handlers are not hoisted when one of them is not delegateable
 export default test({
-	html: `<button>0</button>`,
+	html: `<button>0</button><button>x0</button><button>y0</button>`,
 
 	async test({ assert, target }) {
-		const [button] = target.querySelectorAll('button');
+		const [btn1, btn2, btn3] = target.querySelectorAll('button');
 
-		button.click();
+		btn1.click();
 		await Promise.resolve();
-		assert.htmlEqual(target.innerHTML, '<button>1</button>');
+		assert.htmlEqual(target.innerHTML, '<button>1</button><button>x0</button><button>y0</button>');
 
-		button.dispatchEvent(new MouseEvent('mouseenter'));
+		btn1.dispatchEvent(new MouseEvent('mouseenter'));
 		await Promise.resolve();
-		assert.htmlEqual(target.innerHTML, '<button>2</button>');
+		assert.htmlEqual(target.innerHTML, '<button>2</button><button>x0</button><button>y0</button>');
+
+		btn2.click();
+		await Promise.resolve();
+		assert.htmlEqual(target.innerHTML, '<button>2</button><button>x1</button><button>y0</button>');
+
+		btn3.click();
+		await Promise.resolve();
+		assert.htmlEqual(target.innerHTML, '<button>2</button><button>x1</button><button>y1</button>');
 	}
 });

packages/svelte/tests/runtime-runes/samples/event-attribute-not-hoistable/main.svelte

@@ -1,11 +1,36 @@
+<script context="module">
+	function declared_in_module_scope() {
+		return 'x';
+	}
+	let a = declared_in_module_scope();
+
+	let b = 'x';
+	try {
+		b = doesnt_exist();
+	} catch (e) {
+		b = 'y';
+	}
+</script>
+
 <script>
-	let count = $state(0)
+	let count1 = $state(0);
+	let count2 = $state(0);
+	let count3 = $state(0);
 
 	function increment() {
-		count += 1
+		count1 += 1;
+	}
+	function declared_in_module_scope() {
+		count2 += 1;
+	}
+	function doesnt_exist() {
+		count3 += 1;
 	}
 </script>
 
-<button onclick={increment} onmouseenter={increment}>
-	{count}
-</button>
+<!-- Checks that event handlers are not hoisted when one of them is not delegateable -->
+<button onclick={increment} onmouseenter={increment}>{count1}</button>
+
+<!-- Checks that event handler is not hoisted if the same name is used in the module context -->
+<button onclick={declared_in_module_scope}>{a}{count2}</button>
+<button onclick={doesnt_exist}>{b}{count3}</button>