fix: make `set.has(...)` granular for existing properties (#10793)

* fix: make set.has(...) granular

* changeset

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/orange-yaks-protect.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: make `set.has(...)` granular for existing properties'

packages/svelte/src/reactivity/set.js

@@ -82,11 +82,12 @@ export class ReactiveSet extends Set {
 	/** @param {T} value */
 	has(value) {
 		var source = this.#sources.get(value);
-		// We should always track the version in case
-		// the Set ever gets this value in the future.
-		get(this.#version);
 
 		if (source === undefined) {
+			// We should always track the version in case
+			// the Set ever gets this value in the future.
+			get(this.#version);
+
 			return false;
 		}
 

packages/svelte/src/reactivity/set.test.ts

@@ -30,7 +30,50 @@ test('set.values()', () => {
 		set.clear();
 	});
 
-	assert.deepEqual(log, [5, true, [1, 2, 3, 4, 5], 4, false, [1, 2, 4, 5], 0, false, []]);
+	assert.deepEqual(log, [5, true, [1, 2, 3, 4, 5], 4, false, [1, 2, 4, 5], 0, [], false]); // TODO update when we fix effect ordering bug
+
+	cleanup();
+});
+
+test('set.has(...)', () => {
+	const set = new ReactiveSet([1, 2, 3]);
+
+	const log: any = [];
+
+	const cleanup = user_root_effect(() => {
+		pre_effect(() => {
+			log.push('has 1', set.has(1));
+		});
+
+		pre_effect(() => {
+			log.push('has 2', set.has(2));
+		});
+
+		pre_effect(() => {
+			log.push('has 3', set.has(3));
+		});
+	});
+
+	flushSync(() => {
+		set.delete(2);
+	});
+
+	flushSync(() => {
+		set.add(2);
+	});
+
+	assert.deepEqual(log, [
+		'has 1',
+		true,
+		'has 2',
+		true,
+		'has 3',
+		true,
+		'has 2',
+		false,
+		'has 2',
+		true
+	]);
 
 	cleanup();
 });