Merge branch 'main' into svelte-custom-renderer

.changeset/khaki-states-train.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: properly unlink batches

.changeset/neat-groups-grin.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: settle discarded batch

.changeset/sad-shoes-help.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: resume outro-ed branches if they were kept around

.changeset/swift-terms-exist.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: avoid waterfall-warning when async resolves to same value

documentation/docs/98-reference/.generated/compile-warnings.md

@@ -842,7 +842,7 @@ Reassignments of module-level declarations will not cause reactive statements to
 ### script_unknown_attribute
 
 ```
-Unrecognized attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
+Unrecognised attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
 ```
 
 ### slot_element_deprecated

packages/svelte/messages/compile-warnings/template.md

@@ -107,7 +107,7 @@ This code will work when the component is rendered on the client (which is why t
 
 ## script_unknown_attribute
 
-> Unrecognized attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
+> Unrecognised attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
 
 ## slot_element_deprecated
 

packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js

@@ -213,7 +213,7 @@ export function VariableDeclaration(node, context) {
 							location ? b.literal(location) : undefined
 						);
 
-						call = should_save ? save(call) : b.await(call);
+						call = should_save ? save(call, true) : b.await(call);
 
 						declarations.push(b.declarator(declarator.id, call));
 					} else {
@@ -251,7 +251,7 @@ export function VariableDeclaration(node, context) {
 								location ? b.literal(location) : undefined
 							);
 
-							call = should_save ? save(call) : b.await(call);
+							call = should_save ? save(call, true) : b.await(call);
 						}
 
 						declarations.push(b.declarator(id, call));

packages/svelte/src/compiler/utils/ast.js

@@ -633,7 +633,8 @@ export function has_await_expression(node) {
 /**
  * Turns `await ...` to `(await $.save(...))()`
  * @param {ESTree.Expression} expression
+ * @param {boolean} unset
  */
-export function save(expression) {
+export function save(expression, unset = false) {
-	return b.call(b.await(b.call('$.save', expression)));
+	return b.call(b.await(b.call('$.save', expression, unset && b.true)));
 }

packages/svelte/src/compiler/warnings.js

@@ -804,11 +804,11 @@ export function script_context_deprecated(node) {
 }
 
 /**
- * Unrecognized attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
+ * Unrecognised attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it
  * @param {null | NodeLike} node
  */
 export function script_unknown_attribute(node) {
-	w(node, 'script_unknown_attribute', `Unrecognized attribute — should be one of \`generics\`, \`lang\` or \`module\`. If this exists for a preprocessor, ensure that the preprocessor removes it\nhttps://svelte.dev/e/script_unknown_attribute`);
+	w(node, 'script_unknown_attribute', `Unrecognised attribute — should be one of \`generics\`, \`lang\` or \`module\`. If this exists for a preprocessor, ensure that the preprocessor removes it\nhttps://svelte.dev/e/script_unknown_attribute`);
 }
 
 /**

packages/svelte/src/internal/client/dom/blocks/branches.js

@@ -111,6 +111,8 @@ export class BranchManager {
 			var offscreen = this.#offscreen.get(key);
 
 			if (offscreen) {
+				// effect could have been outro'ed before through a prior batch — resume if necessary
+				resume_effect(offscreen.effect);
 				this.#onscreen.set(key, offscreen.effect);
 				this.#offscreen.delete(key);
 

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

@@ -26,6 +26,7 @@ import {
 	set_reactivity_loss_tracker
 } from './deriveds.js';
 import { aborted } from './effects.js';
+import { queue_micro_task } from '../dom/task.js';
 
 /**
  * @param {Blocker[]} blockers
@@ -152,13 +153,25 @@ export function capture() {
  * `await a + b` becomes `(await $.save(a))() + b`
  * @template T
  * @param {Promise<T>} promise
+ * @param {boolean} unset
  * @returns {Promise<() => T>}
  */
-export async function save(promise) {
+export async function save(promise, unset) {
+	var batch = current_batch;
 	var restore = capture();
 	var value = await promise;
 
 	return () => {
+		if (unset) {
+			// If this is happening outside the context of an async derived,
+			// context will not automatically be unset
+			queue_micro_task(() => {
+				if (batch === current_batch) {
+					unset_context();
+				}
+			});
+		}
+
 		restore();
 		return value;
 	};
@@ -357,15 +370,15 @@ export function wait(blockers) {
  */
 export function increment_pending() {
 	var effect = /** @type {Effect} */ (active_effect);
-	var boundary = /** @type {Boundary} */ (effect.b);
+	var boundary = effect.b; // undefined if called outside the render tree, e.g. a standalone $effect.root
 	var batch = /** @type {Batch} */ (current_batch);
-	var blocking = boundary.is_rendered();
+	var blocking = !!boundary?.is_rendered();
 
-	boundary.update_pending_count(1, batch);
+	boundary?.update_pending_count(1, batch);
 	batch.increment(blocking, effect);
 
 	return () => {
-		boundary.update_pending_count(-1, batch);
+		boundary?.update_pending_count(-1, batch);
 		batch.decrement(blocking, effect);
 	};
 }

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

@@ -393,31 +393,30 @@ export class Batch {
 
 		var next_batch = /** @type {Batch | null} */ (/** @type {unknown} */ (current_batch));
 
-		if (this.linked && this.#pending === 0) {
+		if (this.#pending === 0 && (this.#roots.length === 0 || next_batch !== null)) {
 			this.#unlink();
-		}
 
-		// Order matters here - we need to commit and THEN continue flushing new batches, not the other way around,
+			// Order matters here - we need to commit and THEN continue flushing new batches, not the other way around,
-		// else we could start flushing a new batch and then, if it has pending work, rebase it right afterwards, which is wrong.
+			// else we could start flushing a new batch and then, if it has pending work, rebase it right afterwards, which is wrong.
-		// In sync mode flushSync can cause #commit to wrongfully think that there needs to be a rebase, so we only do it in async mode
+			// In sync mode flushSync can cause #commit to wrongfully think that there needs to be a rebase, so we only do it in async mode
-		// TODO fix the underlying cause, otherwise this will likely regress when non-async mode is removed
+			// TODO fix the underlying cause, otherwise this will likely regress when non-async mode is removed
-		if (async_mode_flag && !this.linked) {
+			if (async_mode_flag) {
-			this.#commit();
+				this.#commit();
-			// Rebases can activate other batches or null it out, therefore restore the new one here
+				// Rebases can activate other batches or null it out, therefore restore the new one here
-			current_batch = next_batch;
+				current_batch = next_batch;
+			}
 		}
 
 		// Edge case: During traversal new branches might create effects that run immediately and set state,
 		// causing an effect and therefore a root to be scheduled again. We need to traverse the current batch
 		// once more in that case - most of the time this will just clean up dirty branches.
 		if (this.#roots.length > 0) {
-			if (next_batch === null) {
+			if (next_batch !== null) {
+				const batch = next_batch;
+				batch.#roots.push(...this.#roots.filter((r) => !batch.#roots.includes(r)));
+			} else {
 				next_batch = this;
-				this.#link();
 			}
-
-			const batch = next_batch;
-			batch.#roots.push(...this.#roots.filter((r) => !batch.#roots.includes(r)));
 		}
 
 		if (next_batch !== null) {
@@ -633,6 +632,7 @@ export class Batch {
 		this.#fork_commit_callbacks.clear();
 
 		this.#unlink();
+		this.#deferred?.resolve();
 	}
 
 	/**
@@ -643,8 +643,6 @@ export class Batch {
 	}
 
 	#commit() {
-		this.#unlink();
-
 		// If there are other pending batches, they now need to be 'rebased' —
 		// in other words, we re-run block/async effects with the newly
 		// committed state, unless the batch in question has a more

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

@@ -230,9 +230,7 @@ export function async_derived(fn, label, location) {
 					signal.f ^= ERROR_VALUE;
 				}
 
-				internal_set(signal, value);
+				if (DEV && location !== undefined && !signal.equals(value)) {
-
-				if (DEV && location !== undefined) {
 					recent_async_deriveds.add(signal);
 
 					setTimeout(() => {
@@ -242,6 +240,8 @@ export function async_derived(fn, label, location) {
 						}
 					});
 				}
+
+				internal_set(signal, value);
 			}
 
 			batch.deactivate();

packages/svelte/tests/runtime-runes/samples/async-async-disconnected-effect-root/main.svelte

@@ -1,11 +0,0 @@
-<script>
-	setTimeout(() => {
-		$effect.root(() => {
-			async function fn() {
-				const value = $derived(await 1);
-				return { get value() { return value } };
-			}
-			fn().then(r => console.log(r.value));
-		})
-	})
-</script>

packages/svelte/tests/runtime-runes/samples/async-branch-reintro/_config.js

@@ -0,0 +1,58 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [inc_count, inc_both, shift] = target.querySelectorAll('button');
+
+		inc_both.click();
+		await tick();
+		inc_count.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>increment count</button>
+			<button>increment both</button>
+			<button>shift</button>
+			0
+			0
+			<button>0</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>increment count</button>
+				<button>increment both</button>
+				<button>shift</button>
+				1
+				2
+				<button>1</button>
+			`
+		);
+
+		const button = /** @type {HTMLButtonElement} */ (target.querySelector('button:last-child'));
+		button.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>increment count</button>
+				<button>increment both</button>
+				<button>shift</button>
+				2
+				2
+				<button>2</button>
+			`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-branch-reintro/main.svelte

@@ -0,0 +1,23 @@
+<script>
+	let count = $state(0);
+	let other = $state(0);
+	let queued = [];
+
+	function push(v) {
+		if (!v) return v;
+
+		return new Promise((resolve) => {
+			queued.push(() => resolve(v));
+		});
+	}
+</script>
+
+<button onclick={() => count++}>increment count</button>
+<button onclick={() => {count++;other++}}>increment both</button>
+<button onclick={() => queued.shift()?.()}>shift</button>
+
+{await push(other)}
+{#if count % 2 === 0}
+	{await push(count)}
+	<button onclick={() => other++}>{other}</button>
+{/if}

packages/svelte/tests/runtime-runes/samples/async-derived-same-value/_config.js

@@ -0,0 +1,19 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: { dev: true },
+	async test({ assert, target, warnings }) {
+		await tick();
+		const [button] = target.querySelectorAll('button');
+
+		button.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>1</button>');
+
+		button.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>1</button>');
+		assert.deepEqual(warnings, []);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-derived-same-value/main.svelte

@@ -0,0 +1,12 @@
+<script>
+	let count = $state(0);
+	let unreactive = $derived(await push(count));
+
+	function push(v) {
+		if (!v) return v;
+
+		return Promise.resolve(1);
+	}
+</script>
+
+<button onclick={() => count++}>{unreactive}</button>

packages/svelte/tests/runtime-runes/samples/async-disconnected-effect-root/_config.js

@@ -1,9 +1,15 @@
+import { tick } from 'svelte';
 import { test } from '../../test';
 
 export default test({
 	// Test that an async derived inside an $effect.root not connected to the component tree still works
 	async test({ assert, logs }) {
 		await new Promise((resolve) => setTimeout(resolve, 10));
-		assert.deepEqual(logs, [1]);
+		assert.deepEqual(logs, [1, 1]);
+		const [button] = document.querySelectorAll('button');
+
+		button.click();
+		await tick();
+		assert.deepEqual(logs, [1, 1, 2]);
 	}
 });

packages/svelte/tests/runtime-runes/samples/async-disconnected-effect-root/main.svelte

@@ -0,0 +1,19 @@
+<script>
+	let increment;
+
+	setTimeout(() => {
+		$effect.root(() => {
+			async function fn() {
+				let count = $state(1);
+				increment = () => { count++; };
+				const value = $derived(await count);
+				$effect.pre(() => console.log(value))
+				return { get value() { return value } };
+			}
+			fn().then(r => console.log(r.value));
+		})
+	})
+
+</script>
+
+<button onclick={() => increment()}>increment</button>

packages/svelte/tests/runtime-runes/samples/async-settled-discard/_config.js

@@ -0,0 +1,37 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		await tick();
+		const [increment, pop] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		pop.click();
+		await tick();
+		assert.deepEqual(logs, ['settled 2', 'settled 2']);
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				2
+				<button>increment</button>
+				<button>pop</button>
+			`
+		);
+
+		pop.click();
+		await tick();
+		assert.deepEqual(logs, ['settled 2', 'settled 2']);
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				2
+				<button>increment</button>
+				<button>pop</button>
+			`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-settled-discard/main.svelte

@@ -0,0 +1,22 @@
+<script>
+	import { settled } from "svelte";
+
+	let count = $state(0);
+	let queued = [];
+
+	function push(v) {
+		if (!v) return v;
+
+		return new Promise((resolve) => {
+			queued.push(() => resolve(v));
+		});
+	}
+</script>
+
+{await push(count)}
+<button onclick={async () => {
+	count++;
+	await settled();
+	console.log('settled ' + count);
+}}>increment</button>
+<button onclick={() => queued.pop()?.()}>pop</button>

packages/svelte/tests/runtime-runes/samples/async-unset-context-after-restore/_config.js

@@ -0,0 +1,14 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, logs }) {
+		await new Promise((resolve) => setTimeout(resolve, 10));
+		assert.deepEqual(logs, [1, 1]);
+		const [button] = document.querySelectorAll('button');
+
+		button.click();
+		await tick();
+		assert.deepEqual(logs, [1, 1, 2]);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-unset-context-after-restore/main.svelte

@@ -0,0 +1,15 @@
+<script>
+	let increment;
+
+	async function fn() {
+		let count = $state(1);
+		increment = () => { count++; };
+		const value = $derived(await count);
+		$effect.pre(() => console.log(value))
+		return { get value() { return value } };
+	}
+	fn().then(r => console.log(r.value));
+
+</script>
+
+<button onclick={() => increment()}>increment</button>

packages/svelte/tests/validator/samples/script-invalid-spread-attribute/warnings.json

@@ -1,7 +1,7 @@
 [
 	{
 		"code": "script_unknown_attribute",
-		"message": "Unrecognized attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it",
+		"message": "Unrecognised attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it",
 		"start": {
 			"column": 8,
 			"line": 1

packages/svelte/tests/validator/samples/script-unknown-attribute/warnings.json

@@ -1,7 +1,7 @@
 [
 	{
 		"code": "script_unknown_attribute",
-		"message": "Unrecognized attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it",
+		"message": "Unrecognised attribute — should be one of `generics`, `lang` or `module`. If this exists for a preprocessor, ensure that the preprocessor removes it",
 		"start": {
 			"column": 8,
 			"line": 1