maintain context for contextual binding handlers - fixes #2146

src/compile/render-dom/wrappers/Element/index.ts

@@ -290,13 +290,8 @@ export default class ElementWrapper extends Wrapper {
 			});
 		}
 
-		const eventHandlerOrBindingUsesComponent = (
-			this.bindings.length > 0 ||
-			this.node.handlers.some(handler => handler.usesComponent)
-		);
-
 		const eventHandlerOrBindingUsesContext = (
-			this.bindings.some(binding => binding.node.usesContext) ||
+			this.bindings.some(binding => binding.handler.usesContext) ||
 			this.node.handlers.some(handler => handler.usesContext) ||
 			this.node.actions.some(action => action.usesContext)
 		);

test/runtime/samples/binding-input-checkbox-deep-contextual-b/_config.js

@@ -0,0 +1,50 @@
+export default {
+	html: `
+		<div>
+			<input type="checkbox"><p>one</p>
+		</div>
+		<div>
+			<input type="checkbox"><p>two</p>
+		</div>
+		<div>
+			<input type="checkbox"><p>three</p>
+		</div>
+	`,
+
+	ssrHtml: `
+		<div>
+			<input type="checkbox"><p>one</p>
+		</div>
+		<div>
+			<input type="checkbox"><p>two</p>
+		</div>
+		<div>
+			<input type="checkbox"><p>three</p>
+		</div>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const inputs = [ ...target.querySelectorAll('input') ];
+
+		const event = new window.Event('change');
+
+		inputs[1].checked = true;
+		await inputs[1].dispatchEvent(event);
+
+		await component.clear();
+
+		assert.htmlEqual(target.innerHTML, `
+			<div><input type="checkbox"><p>one</p></div>
+			<div><input type="checkbox"><p>three</p></div>
+		`);
+
+		inputs[1].checked = true;
+		await inputs[1].dispatchEvent(event);
+
+		await component.clear();
+
+		assert.htmlEqual(target.innerHTML, `
+			<div><input type="checkbox"><p>one</p></div>
+		`);
+	}
+};

test/runtime/samples/binding-input-checkbox-deep-contextual-b/main.svelte

@@ -0,0 +1,18 @@
+<script>
+	let todos = [
+		{ done: false, text: 'one' },
+		{ done: false, text: 'two' },
+		{ done: false, text: 'three' }
+	];
+
+	export function clear() {
+		todos = todos.filter(t => !t.done);
+	}
+</script>
+
+{#each todos as todo, i}
+	<div>
+		<input type=checkbox bind:checked={todo.done}>
+		<p>{todo.text}</p>
+	</div>
+{/each}