add commented-out test, todo investigate

packages/svelte/tests/runtime-runes/samples/async-each-overlap/_config.js

@@ -0,0 +1,102 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	skip: true,
+	async test({ assert, target }) {
+		const [add, shift] = target.querySelectorAll('button');
+
+		add.click();
+		await tick();
+		add.click();
+		await tick();
+		add.click();
+		await tick();
+
+		// TODO pending count / number of pushes is off
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>add</button>
+			<button>shift</button>
+			<p>pending=6 values.length=1 values=[1]</p>
+			<div>not keyed:
+				<div>1</div>
+			</div>
+			<div>keyed:
+				<div>1</div>
+			</div>
+		`
+		);
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>add</button>
+			<button>shift</button>
+			<p>pending=4 values.length=2 values=[1,2]</p>
+			<div>not keyed:
+				<div>1</div>
+				<div>2</div>
+			</div>
+			<div>keyed:
+				<div>1</div>
+				<div>2</div>
+			</div>
+		`
+		);
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>add</button>
+			<button>shift</button>
+			<p>pending=2 values.length=3 values=[1,2,3]</p>
+			<div>not keyed:
+				<div>1</div>
+				<div>2</div>
+				<div>3</div>
+			</div>
+			<div>keyed:
+				<div>1</div>
+				<div>2</div>
+				<div>3</div>
+			</div>
+		`
+		);
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>add</button>
+			<button>shift</button>
+			<p>pending=0 values.length=4 values=[1,2,3,4]</p>
+			<div>not keyed:
+				<div>1</div>
+				<div>2</div>
+				<div>3</div>
+				<div>4</div>
+			</div>
+			<div>keyed:
+				<div>1</div>
+				<div>2</div>
+				<div>3</div>
+				<div>4</div>
+			</div>
+		`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-each-overlap/main.svelte

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+<script>
+	let values = $state([1]);
+
+	const queue = [];
+
+	function push(v) {
+		if (v === 1) return v;
+
+		const p = Promise.withResolvers();
+		queue.push(() => p.resolve(v));
+		return p.promise;
+	}
+
+	function shift() {
+		const fn = queue.shift();
+		if (fn) fn();
+	}
+
+	function addValue() {
+		values.push(values.length+1);
+	}
+</script>
+
+<button onclick={addValue}>add</button>
+<button onclick={shift}>shift</button>
+
+<p>
+	pending={$effect.pending()}
+	values.length={values.length}
+	values=[{values}]
+</p>
+
+<div>
+	not keyed:
+	{#each values as v}
+		<div>
+			{await push(v)}
+		</div>
+	{/each}
+</div>
+<div>
+	keyed:
+	{#each values as v(v)}
+		<div>
+			{await push(v)}
+		</div>
+	{/each}
+</div>