fix: depend on reads of deriveds created within reaction (async mode)

.changeset/gold-eels-lay.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: depend on reads of deriveds created within reaction (async mode)

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -29,7 +29,7 @@ import * as w from '../warnings.js';
 import { async_effect, destroy_effect } from './effects.js';
 import { inspect_effects, internal_set, set_inspect_effects, source } from './sources.js';
 import { get_stack } from '../dev/tracing.js';
-import { tracing_mode_flag } from '../../flags/index.js';
+import { async_mode_flag, tracing_mode_flag } from '../../flags/index.js';
 import { Boundary } from '../dom/blocks/boundary.js';
 import { component_context } from '../context.js';
 import { UNINITIALIZED } from '../../../constants.js';
@@ -231,7 +231,7 @@ export function async_derived(fn, location) {
 export function user_derived(fn) {
 	const d = derived(fn);
 
-	push_reaction_value(d);
+	if (!async_mode_flag) push_reaction_value(d);
 
 	return d;
 }

packages/svelte/tests/runtime-runes/samples/derived-in-expression/_config.js

@@ -0,0 +1,74 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	// In non-async mode we're not reacting to deriveds read in the same context they're defined in
+	skip_no_async: true,
+	test({ assert, target, logs }) {
+		const [a, b] = target.querySelectorAll('button');
+
+		flushSync(() => a?.click());
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>a</button>
+				<button>b</button>
+				<p>1/0</p
+			`
+		);
+
+		flushSync(() => a?.click());
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>a</button>
+				<button>b</button>
+				<p>2/0</p
+			`
+		);
+
+		flushSync(() => b?.click());
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>a</button>
+				<button>b</button>
+				<p>2/1</p
+			`
+		);
+
+		flushSync(() => b?.click());
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>a</button>
+				<button>b</button>
+				<p>2/2</p
+			`
+		);
+
+		assert.deepEqual(logs, [
+			// init
+			'a',
+			'b',
+			'effect a',
+			'effect b',
+			// click a
+			'a',
+			'effect a',
+			// click a
+			'a',
+			'effect a',
+			// click b
+			'a',
+			'b',
+			'effect a',
+			'effect b',
+			// click b
+			'a',
+			'b',
+			'effect a',
+			'effect b'
+		]);
+	}
+});

packages/svelte/tests/runtime-runes/samples/derived-in-expression/main.svelte

@@ -0,0 +1,30 @@
+<script>
+	let object = $state.raw({ a: 0, b: 0 });
+
+	function a() {
+		console.log('a');
+		return object.a;
+	}
+
+	function b() {
+		console.log('b');
+		let double = $derived(object.b)
+		return double;
+	}
+
+	$effect(() => {
+		object.a;
+		console.log('effect a');
+	})
+
+	$effect(() => {
+		const b = $derived(object.b);
+		b;
+		console.log('effect b');
+	})
+</script>
+
+<button onclick={() => object = { ...object, a: object.a + 1 }}>a</button>
+<button onclick={() => object = { ...object, b: object.b + 1 }}>b</button>
+
+<p>{a()}/{b()}</p>

packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js

@@ -13,10 +13,11 @@ export default test({
 			target.innerHTML,
 			`
 				<button>increment</button>
-				<p>1/2</p
+				<p>1/2</p>
+				<p>1/2</p>
 			`
 		);
 
-		assert.deepEqual(logs, [0, 0]);
+		assert.deepEqual(logs, [0, 0, 0, 0]);
 	}
 });

packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte

@@ -17,10 +17,14 @@
 	$effect(() => {
 		foo = new Foo();
 	});
+
+	let bar = $derived(new Foo());
 </script>
 
-<button onclick={() => foo.increment()}>increment</button>
+<button onclick={() => {foo.increment(); bar.increment()}}>increment</button>
 
 {#if foo}
 	<p>{foo.value}/{foo.double}</p>
 {/if}
+
+<p>{bar.value}/{bar.double}</p>