From 9d9b64b94eb4a1b700d15da9fa08e793ed6ded06 Mon Sep 17 00:00:00 2001
From: raythurnvoid <53383860+raythurnvoid@users.noreply.github.com>
Date: Sun, 29 Jun 2025 16:46:58 +0100
Subject: [PATCH] Add tests for props old values in onDestroy hooks to prevent
 regressions

---
 .../Component.svelte                          | 11 ++++
 .../_config.js                                | 63 +++++++++++++++++++
 .../main.svelte                               | 52 +++++++++++++++
 .../Component.svelte                          | 14 +++++
 .../_config.js                                | 63 +++++++++++++++++++
 .../main.svelte                               | 52 +++++++++++++++
 .../Component.svelte                          | 11 ++++
 .../_config.js                                | 49 +++++++++++++++
 .../main.svelte                               | 41 ++++++++++++
 9 files changed, 356 insertions(+)
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/Component.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/Component.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/Component.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/main.svelte

diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/Component.svelte b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/Component.svelte
new file mode 100644
index 0000000000..40d6b1c2fb
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/Component.svelte
@@ -0,0 +1,11 @@
+<script>
+	import { onDestroy } from 'svelte';
+
+	let { checked = $bindable(), count = $bindable() } = $props();
+
+	onDestroy(() => {
+		console.log(`${count} ${checked}`);
+	});
+</script>
+
+<p>Count: {count}</p>
diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/_config.js b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/_config.js
new file mode 100644
index 0000000000..07ea5af153
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/_config.js
@@ -0,0 +1,63 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, logs, target }) {
+		/** @type {HTMLButtonElement | null} */
+		const increment_btn = target.querySelector('#increment');
+		/** @type {HTMLButtonElement | null} */
+		const toggle_btn = target.querySelector('#toggle');
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 0');
+		}
+
+		// Click increment: count=1
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 1');
+		}
+
+		// Click increment again: count=2, components with count < 2 should unmount and log old values
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 2');
+		}
+
+		// Toggle show to hide components that depend on show
+		flushSync(() => {
+			toggle_btn?.click();
+		});
+
+		// Should log old values during cleanup from the six components guarded by `count < 2`:
+		// 1. Component with bind: "1 true"
+		// 2. Component with spread: "1 true"
+		// 3. Component with normal props: "1 true"
+		// 4. Runes dynamic component with bind: "1 true"
+		// 5. Runes dynamic component with spread: "1 true"
+		// 6. Runes dynamic component with normal props: "1 true"
+		// Then from the four components guarded by `show`:
+		// 7. Component with bind (show): "2 true" (old value of checked)
+		// 8. Runes dynamic component with bind (show): "2 true"
+		// 9. Runes dynamic component with spread (show): "2 true"
+		// 10. Runes dynamic component with normal props (show): "2 true"
+		assert.deepEqual(logs, [
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'2 true',
+			'2 true',
+			'2 true',
+			'2 true'
+		]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/main.svelte b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/main.svelte
new file mode 100644
index 0000000000..592c46ff42
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-no-setter/main.svelte
@@ -0,0 +1,52 @@
+<script>
+	import Component from './Component.svelte';
+
+	let show = $state(true);
+	let count = $state(0);
+	let spread = $derived({ checked: show, count });
+
+	// Runes dynamic component pattern
+	let DynComponent1 = $derived(count < 2 ? Component : undefined);
+	let DynComponent2 = $derived(show ? Component : undefined);
+</script>
+
+<button id="increment" onclick={() => count++}>Increment count</button>
+<button id="toggle" onclick={() => (show = !show)}>Toggle show</button>
+
+<!-- count with bind -->
+{#if count < 2}
+	<Component bind:count bind:checked={show} />
+{/if}
+
+<!-- spread syntax -->
+{#if count < 2}
+	<Component {...spread} />
+{/if}
+
+<!-- normal prop -->
+{#if count < 2}
+	<Component {count} checked={show} />
+{/if}
+
+<!-- prop only accessed in destroy -->
+{#if show}
+	<Component bind:count bind:checked={show} />
+{/if}
+
+<!-- runes dynamic component pattern -->
+<DynComponent1 bind:count bind:checked={show} />
+
+<!-- runes dynamic component pattern with spread -->
+<DynComponent1 {...spread} />
+
+<!-- runes dynamic component pattern with normal props -->
+<DynComponent1 {count} checked={show} />
+
+<!-- runes dynamic component pattern (show) -->
+<DynComponent2 bind:count bind:checked={show} />
+
+<!-- runes dynamic component pattern with spread (show) -->
+<DynComponent2 {...spread} />
+
+<!-- runes dynamic component pattern with normal props (show) -->
+<DynComponent2 {count} checked={show} />
diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/Component.svelte b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/Component.svelte
new file mode 100644
index 0000000000..cc47017946
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/Component.svelte
@@ -0,0 +1,14 @@
+<script>
+	import { onDestroy } from 'svelte';
+
+	let { checked = $bindable(), count = $bindable() } = $props();
+
+	onDestroy(() => {
+		console.log(`${count} ${checked}`);
+	});
+</script>
+
+<p>Count: {count}</p>
+
+<button onclick={() => count--}>Decrement count</button>
+<button onclick={() => (checked = !checked)}>Toggle checked</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/_config.js b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/_config.js
new file mode 100644
index 0000000000..07ea5af153
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/_config.js
@@ -0,0 +1,63 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, logs, target }) {
+		/** @type {HTMLButtonElement | null} */
+		const increment_btn = target.querySelector('#increment');
+		/** @type {HTMLButtonElement | null} */
+		const toggle_btn = target.querySelector('#toggle');
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 0');
+		}
+
+		// Click increment: count=1
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 1');
+		}
+
+		// Click increment again: count=2, components with count < 2 should unmount and log old values
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 2');
+		}
+
+		// Toggle show to hide components that depend on show
+		flushSync(() => {
+			toggle_btn?.click();
+		});
+
+		// Should log old values during cleanup from the six components guarded by `count < 2`:
+		// 1. Component with bind: "1 true"
+		// 2. Component with spread: "1 true"
+		// 3. Component with normal props: "1 true"
+		// 4. Runes dynamic component with bind: "1 true"
+		// 5. Runes dynamic component with spread: "1 true"
+		// 6. Runes dynamic component with normal props: "1 true"
+		// Then from the four components guarded by `show`:
+		// 7. Component with bind (show): "2 true" (old value of checked)
+		// 8. Runes dynamic component with bind (show): "2 true"
+		// 9. Runes dynamic component with spread (show): "2 true"
+		// 10. Runes dynamic component with normal props (show): "2 true"
+		assert.deepEqual(logs, [
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'1 true',
+			'2 true',
+			'2 true',
+			'2 true',
+			'2 true'
+		]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/main.svelte b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/main.svelte
new file mode 100644
index 0000000000..592c46ff42
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/bindable-props-cleanup-with-setter/main.svelte
@@ -0,0 +1,52 @@
+<script>
+	import Component from './Component.svelte';
+
+	let show = $state(true);
+	let count = $state(0);
+	let spread = $derived({ checked: show, count });
+
+	// Runes dynamic component pattern
+	let DynComponent1 = $derived(count < 2 ? Component : undefined);
+	let DynComponent2 = $derived(show ? Component : undefined);
+</script>
+
+<button id="increment" onclick={() => count++}>Increment count</button>
+<button id="toggle" onclick={() => (show = !show)}>Toggle show</button>
+
+<!-- count with bind -->
+{#if count < 2}
+	<Component bind:count bind:checked={show} />
+{/if}
+
+<!-- spread syntax -->
+{#if count < 2}
+	<Component {...spread} />
+{/if}
+
+<!-- normal prop -->
+{#if count < 2}
+	<Component {count} checked={show} />
+{/if}
+
+<!-- prop only accessed in destroy -->
+{#if show}
+	<Component bind:count bind:checked={show} />
+{/if}
+
+<!-- runes dynamic component pattern -->
+<DynComponent1 bind:count bind:checked={show} />
+
+<!-- runes dynamic component pattern with spread -->
+<DynComponent1 {...spread} />
+
+<!-- runes dynamic component pattern with normal props -->
+<DynComponent1 {count} checked={show} />
+
+<!-- runes dynamic component pattern (show) -->
+<DynComponent2 bind:count bind:checked={show} />
+
+<!-- runes dynamic component pattern with spread (show) -->
+<DynComponent2 {...spread} />
+
+<!-- runes dynamic component pattern with normal props (show) -->
+<DynComponent2 {count} checked={show} />
diff --git a/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/Component.svelte b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/Component.svelte
new file mode 100644
index 0000000000..1a95f1edf5
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/Component.svelte
@@ -0,0 +1,11 @@
+<script>
+	import { onDestroy } from 'svelte';
+
+	let { checked, count } = $props();
+
+	onDestroy(() => {
+		console.log(`${count} ${checked}`);
+	});
+</script>
+
+<p>Count: {count}</p>
diff --git a/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/_config.js b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/_config.js
new file mode 100644
index 0000000000..3d73bfd1a9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/_config.js
@@ -0,0 +1,49 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, logs, target }) {
+		/** @type {HTMLButtonElement | null} */
+		const increment_btn = target.querySelector('#increment');
+		/** @type {HTMLButtonElement | null} */
+		const toggle_btn = target.querySelector('#toggle');
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 0');
+		}
+
+		// Click increment: count=1
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 1');
+		}
+
+		// Click increment again: count=2, components with count < 2 should unmount and log old values
+		flushSync(() => {
+			increment_btn?.click();
+		});
+
+		for (const p of target.querySelectorAll('p')) {
+			assert.equal(p.innerHTML, 'Count: 2');
+		}
+
+		// Toggle show to hide components that depend on show
+		flushSync(() => {
+			toggle_btn?.click();
+		});
+
+		// Should log old values during cleanup from the four components guarded by `count < 2`:
+		// 1. Component with normal props: "1 true"
+		// 2. Component with spread: "1 true"
+		// 3. Runes dynamic component with normal props: "1 true"
+		// 4. Runes dynamic component with spread: "1 true"
+		// Then from the three components guarded by `show`:
+		// 5. Component with normal props (show): "2 true" (old value of checked)
+		// 6. Runes dynamic component with normal props (show): "2 true"
+		// 7. Runes dynamic component with spread (show): "2 true"
+		assert.deepEqual(logs, ['1 true', '1 true', '1 true', '1 true', '2 true', '2 true', '2 true']);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/main.svelte b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/main.svelte
new file mode 100644
index 0000000000..8bc6abfa4d
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/regular-props-cleanup-old-value/main.svelte
@@ -0,0 +1,41 @@
+<script>
+	import Component from './Component.svelte';
+
+	let show = $state(true);
+	let count = $state(0);
+	let spread = $derived({ checked: show, count });
+
+	// Runes dynamic component pattern
+	let DynComponent1 = $derived(count < 2 ? Component : undefined);
+	let DynComponent2 = $derived(show ? Component : undefined);
+</script>
+
+<button id="increment" onclick={() => count++}>Increment count</button>
+<button id="toggle" onclick={() => (show = !show)}>Toggle show</button>
+
+<!-- normal props -->
+{#if count < 2}
+	<Component {count} checked={show} />
+{/if}
+
+<!-- spread syntax -->
+{#if count < 2}
+	<Component {...spread} />
+{/if}
+
+<!-- prop only accessed in destroy -->
+{#if show}
+	<Component {count} checked={show} />
+{/if}
+
+<!-- runes dynamic component pattern with normal props -->
+<DynComponent1 {count} checked={show} />
+
+<!-- runes dynamic component pattern with spread -->
+<DynComponent1 {...spread} />
+
+<!-- runes dynamic component pattern (show) with normal props -->
+<DynComponent2 {count} checked={show} />
+
+<!-- runes dynamic component pattern with spread (show) -->
+<DynComponent2 {...spread} />