only invalidate referenced values

src/compile/Component.ts

@@ -789,6 +789,10 @@ export default class Component {
 			return `${name.slice(1)}.set(${name})`
 		}
 
+		if (variable && !variable.referenced && !variable.is_reactive_dependency && !variable.export_name && !name.startsWith('$$')) {
+			return value || name;
+		}
+
 		if (value) {
 			return `$$invalidate('${name}', ${value})`;
 		}
@@ -1120,8 +1124,9 @@ export default class Component {
 							if (!assignee_nodes.has(identifier)) {
 								const { name } = identifier;
 								const owner = scope.find_owner(name);
-								const component_var = component.var_lookup.get(name);
-								const is_writable_or_mutated = component_var && (component_var.writable || component_var.mutated);
+								const variable = component.var_lookup.get(name);
+								if (variable) variable.is_reactive_dependency = true;
+								const is_writable_or_mutated = variable && (variable.writable || variable.mutated);
 								if (
 									(!owner || owner === component.instance_scope) &&
 									(name[0] === '$' || is_writable_or_mutated)

src/compile/render-dom/index.ts

@@ -203,8 +203,10 @@ export default function dom(
 							if (variable && (variable.hoistable || variable.global || variable.module)) return;
 
 							if (single && !(variable.subscribable && variable.reassigned)) {
-								code.prependRight(node.start, `$$invalidate('${name}', `);
-								code.appendLeft(node.end, `)`);
+								if (variable.referenced || variable.is_reactive_dependency || variable.export_name) {
+									code.prependRight(node.start, `$$invalidate('${name}', `);
+									code.appendLeft(node.end, `)`);
+								}
 							} else {
 								pending_assignments.add(name);
 							}

src/interfaces.ts

@@ -133,4 +133,5 @@ export interface Var {
 	initialised?: boolean;
 	hoistable?: boolean;
 	subscribable?: boolean;
-}
+	is_reactive_dependency?: boolean;
+}

test/js/samples/reactive-values-non-topologically-ordered/expected.js

@@ -29,7 +29,7 @@ function instance($$self, $$props, $$invalidate) {
 
 	$$self.$$.update = ($$dirty = { x: 1, b: 1 }) => {
 		if ($$dirty.x) { $$invalidate('b', b = x); }
-		if ($$dirty.b) { $$invalidate('a', a = b); }
+		if ($$dirty.b) { a = b; }
 	};
 
 	return { x };

test/js/samples/reactive-values-non-writable-dependencies/expected.js

@@ -17,26 +17,25 @@ function create_fragment(ctx) {
 	};
 }
 
-let a = 1;
-
-let b = 2;
-
 function instance($$self, $$props, $$invalidate) {
-
+	let { a = 1, b = 2 } = $$props;
 
-	let max;
+	$$self.$set = $$props => {
+		if ('a' in $$props) $$invalidate('a', a = $$props.a);
+		if ('b' in $$props) $$invalidate('b', b = $$props.b);
+	};
 
 	$$self.$$.update = ($$dirty = { a: 1, b: 1 }) => {
-		if ($$dirty.a || $$dirty.b) { $$invalidate('max', max = Math.max(a, b)); }
+		if ($$dirty.a || $$dirty.b) { console.log('max', Math.max(a, b)); }
 	};
 
-	return {};
+	return { a, b };
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, []);
+		init(this, options, instance, create_fragment, safe_not_equal, ["a", "b"]);
 	}
 }
 

test/js/samples/reactive-values-non-writable-dependencies/input.svelte

@@ -1,7 +1,6 @@
 <script>
-	let a = 1;
-	let b = 2;
+	export let a = 1;
+	export let b = 2;
 
-	let max;
-	$: max = Math.max(a, b);
+	$: console.log('max', Math.max(a, b));
 </script>

test/js/samples/unreferenced-state-not-invalidated/expected.js

@@ -0,0 +1,78 @@
+/* generated by Svelte vX.Y.Z */
+import {
+	SvelteComponent,
+	append,
+	detach,
+	element,
+	init,
+	insert,
+	noop,
+	safe_not_equal,
+	set_data,
+	text
+} from "svelte/internal";
+import { onMount } from "svelte";
+
+function create_fragment(ctx) {
+	var p, t;
+
+	return {
+		c() {
+			p = element("p");
+			t = text(ctx.y);
+		},
+
+		m(target, anchor) {
+			insert(target, p, anchor);
+			append(p, t);
+		},
+
+		p(changed, ctx) {
+			if (changed.y) {
+				set_data(t, ctx.y);
+			}
+		},
+
+		i: noop,
+		o: noop,
+
+		d(detaching) {
+			if (detaching) {
+				detach(p);
+			}
+		}
+	};
+}
+
+function instance($$self, $$props, $$invalidate) {
+	let a, b, c;
+
+	onMount(() => {
+		const interval = setInterval(() => {
+			$$invalidate('b', b += 1);
+			c += 1;
+
+			console.log(b, c);
+		}, 1000);
+
+		return () => clearInterval(interval);
+	});
+
+	let x, y;
+
+	$$self.$$.update = ($$dirty = { a: 1, b: 1 }) => {
+		if ($$dirty.a) { x = a * 2; }
+		if ($$dirty.b) { $$invalidate('y', y = b * 2); }
+	};
+
+	return { y };
+}
+
+class Component extends SvelteComponent {
+	constructor(options) {
+		super();
+		init(this, options, instance, create_fragment, safe_not_equal, []);
+	}
+}
+
+export default Component;

test/js/samples/unreferenced-state-not-invalidated/input.svelte

@@ -0,0 +1,21 @@
+<script>
+	import { onMount } from 'svelte';
+
+	let a, b, c;
+
+	onMount(() => {
+		const interval = setInterval(() => {
+			b += 1;
+			c += 1;
+
+			console.log(b, c);
+		}, 1000);
+
+		return () => clearInterval(interval);
+	});
+
+	$: x = a * 2;
+	$: y = b * 2;
+</script>
+
+<p>{y}</p>

test/runtime/samples/immutable-nested/Nested.svelte

@@ -1,7 +1,7 @@
 <script>
 	import { beforeUpdate, onMount } from 'svelte';
 
-	let mounted;
+	let mounted = false;
 	export let count = 0;
 	export let foo = { bar: 'baz' };
 
@@ -14,4 +14,5 @@
 	});
 </script>
 
-<h3>Called {count} times.</h3>
+<h3>Called {count} times.</h3>
+<p>{foo.bar} {mounted}</p>

test/runtime/samples/immutable-nested/_config.js

@@ -1,16 +1,35 @@
 export default {
 	immutable: true,
 
-	html: `<div><h3>Called 1 times.</h3></div>`,
+	html: `
+		<div>
+			<h3>Called 1 times.</h3>
+			<p>baz true</p>
+		</div>
+	`,
 
-	ssrHtml: `<div><h3>Called 0 times.</h3></div>`,
+	ssrHtml: `
+		<div>
+			<h3>Called 0 times.</h3>
+			<p>baz false</p>
+		</div>`,
 
-	test({ assert, component, target, window }) {
+	test({ assert, component, target }) {
 		var nested = component.nested;
 
-		assert.htmlEqual(target.innerHTML, `<div><h3>Called 1 times.</h3></div>`);
+		assert.htmlEqual(target.innerHTML, `
+			<div>
+				<h3>Called 1 times.</h3>
+				<p>baz true</p>
+			</div>
+		`);
 
 		nested.foo = nested.foo;
-		assert.htmlEqual(target.innerHTML, `<div><h3>Called 1 times.</h3></div>`);
+		assert.htmlEqual(target.innerHTML, `
+			<div>
+				<h3>Called 1 times.</h3>
+				<p>baz true</p>
+			</div>
+		`);
 	}
 };

test/runtime/samples/immutable-nested/main.svelte

@@ -5,5 +5,5 @@
 </script>
 
 <div>
-  <Nested bind:this={nested} />
+	<Nested bind:this={nested} />
 </div>