fix: adjust event delegation heuristics (#9581)

Fixes #9561

.changeset/thirty-impalas-repair.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: adjust event delegation heuristics

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

@@ -175,7 +175,7 @@ function get_delegated_event(node, context) {
 			// Bail-out if we reference anything from the EachBlock (for now) that mutates in non-runes mode,
 			((!context.state.analysis.runes && binding.kind === 'each') ||
 				// or any normal not reactive bindings that are mutated.
-				(binding.kind === 'normal' && context.state.analysis.runes) ||
+				binding.kind === 'normal' ||
 				// or any reactive imports (those are rewritten) (can only happen in legacy mode)
 				(binding.kind === 'state' && binding.declaration_kind === 'import')) &&
 			binding.mutated

packages/svelte/tests/runtime-legacy/samples/event-handler-mutation-scope/_config.js

@@ -0,0 +1,21 @@
+import { flushSync } from 'svelte';
+import { ok, test } from '../../test';
+
+export default test({
+	test({ assert, component, target, window }) {
+		const button = target.querySelector('button');
+		ok(button);
+
+		flushSync(() => {
+			button.click();
+		});
+
+		assert.deepEqual(component.log, ['1 - 1']);
+
+		flushSync(() => {
+			button.click();
+		});
+
+		assert.deepEqual(component.log, ['1 - 1', '2 - 2']);
+	}
+});

packages/svelte/tests/runtime-legacy/samples/event-handler-mutation-scope/main.svelte

@@ -0,0 +1,16 @@
+<script>
+	export let log = [];
+	let referenced_directly = 0;
+	let not_referenced_directly = 0;
+	let css_based_on_not_referenced = '';
+
+	function click() {
+		referenced_directly += 1;
+		not_referenced_directly += 1;
+		css_based_on_not_referenced = not_referenced_directly % 2 == 1 ? 'background-color: red' : '';
+		log.push(referenced_directly + ' - ' + not_referenced_directly); //only referenced_directly is increasing
+	}
+</script>
+
+<button on:click={click} style={css_based_on_not_referenced}> increase both </button>
+{referenced_directly}