fix compound assignment dependencies in reactive statements (#3634)

src/compiler/compile/Component.ts

@@ -1265,10 +1265,16 @@ export default class Component {
 						}
 
 						if (node.type === 'AssignmentExpression') {
-							extract_identifiers(get_object(node.left)).forEach(node => {
+							const left = get_object(node.left);
+
+							extract_identifiers(left).forEach(node => {
 								assignee_nodes.add(node);
 								assignees.add(node.name);
 							});
+
+							if (node.operator !== '=') {
+								dependencies.add(left.name);
+							}
 						} else if (node.type === 'UpdateExpression') {
 							const identifier = get_object(node.argument);
 							assignees.add(identifier.name);

test/runtime/samples/reactive-compound-operator/_config.js

@@ -0,0 +1,27 @@
+export default {
+	html: `
+		<button>+1</button>
+		<p>count: 0</p>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const click = new window.MouseEvent('click');
+		const button = target.querySelector('button');
+
+		await button.dispatchEvent(click);
+
+		assert.equal(component.x, 2);
+		assert.htmlEqual(target.innerHTML, `
+			<button>+1</button>
+			<p>count: 2</p>
+		`);
+
+		await button.dispatchEvent(click);
+
+		assert.equal(component.x, 6);
+		assert.htmlEqual(target.innerHTML, `
+			<button>+1</button>
+			<p>count: 6</p>
+		`);
+	}
+};

test/runtime/samples/reactive-compound-operator/main.svelte

@@ -0,0 +1,8 @@
+<script>
+	export let x = 0;
+
+	$: x *= 2;
+</script>
+
+<button on:click='{() => x += 1}'>+1</button>
+<p>count: {x}</p>

test/runtime/samples/reactive-update-expression/_config.js

@@ -0,0 +1,29 @@
+export default {
+	html: `
+	<button>+1</button>
+	<p>count: 1</p>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const click = new window.MouseEvent('click');
+		const button = target.querySelector('button');
+
+		assert.equal(component.x, 1);
+
+		await button.dispatchEvent(click);
+
+		assert.equal(component.x, 3);
+		assert.htmlEqual(target.innerHTML, `
+			<button>+1</button>
+			<p>count: 3</p>
+		`);
+
+		await button.dispatchEvent(click);
+
+		assert.equal(component.x, 5);
+		assert.htmlEqual(target.innerHTML, `
+			<button>+1</button>
+			<p>count: 5</p>
+		`);
+	}
+};

test/runtime/samples/reactive-update-expression/main.svelte

@@ -0,0 +1,12 @@
+<script>
+	export let x = 0;
+
+  $: x++;
+
+  function onClick() {
+    x += 1;
+  }
+</script>
+
+<button on:click='{() => x += 1}'>+1</button>
+<p>count: {x}</p>