Merge branch 'main' into task-16961

Author: 7nik

.changeset/dirty-planes-tell.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: change title only after any pending work has completed

.changeset/legal-mangos-peel.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: preserve symbols when creating derived rest properties

.changeset/sixty-comics-bow.md

@@ -135,6 +135,54 @@ If a `<svelte:boundary>` with a `pending` snippet is encountered during SSR, tha
 
 > [!NOTE] In the future, we plan to add a streaming implementation that renders the content in the background.
 
+## Forking
+
+The [`fork(...)`](svelte#fork) API, added in 5.42, makes it possible to run `await` expressions that you _expect_ to happen in the near future. This is mainly intended for frameworks like SvelteKit to implement preloading when (for example) users signal an intent to navigate.
+
+```svelte
+<script>
+	import { fork } from 'svelte';
+	import Menu from './Menu.svelte';
+
+	let open = $state(false);
+
+	/** @type {import('svelte').Fork | null} */
+	let pending = null;
+
+	function preload() {
+		pending ??= fork(() => {
+			open = true;
+		});
+	}
+
+	function discard() {
+		pending?.discard();
+		pending = null;
+	}
+</script>
+
+<button
+	onfocusin={preload}
+	onfocusout={discard}
+	onpointerenter={preload}
+	onpointerleave={discard}
+	onclick={() => {
+		pending?.commit();
+		pending = null;
+
+		// in case `pending` didn't exist
+		// (if it did, this is a no-op)
+		open = true;
+	}}
+>open menu</button>
+
+{#if open}
+	<!-- any async work inside this component will start
+	     as soon as the fork is created -->
+	<Menu onclose={() => open = false} />
+{/if}
+```
+
 ## Caveats
 
 As an experimental feature, the details of how `await` is handled (and related APIs like `$effect.pending()`) are subject to breaking changes outside of a semver major release, though we intend to keep such changes to a bare minimum.

documentation/docs/03-template-syntax/19-await-expressions.md

@@ -130,6 +130,12 @@ $effect(() => {
 
 Often when encountering this issue, the value in question shouldn't be state (for example, if you are pushing to a `logs` array in an effect, make `logs` a normal array rather than `$state([])`). In the rare cases where you really _do_ need to write to state in an effect — [which you should avoid]($effect#When-not-to-use-$effect) — you can read the state with [untrack](svelte#untrack) to avoid adding it as a dependency.
 
+### experimental_async_fork
+
+```
+Cannot use `fork(...)` unless the `experimental.async` compiler option is `true`
+```
+
 ### flush_sync_in_effect
 
 ```
@@ -140,6 +146,18 @@ The `flushSync()` function can be used to flush any pending effects synchronousl
 
 This restriction only applies when using the `experimental.async` option, which will be active by default in Svelte 6.
 
+### fork_discarded
+
+```
+Cannot commit a fork that was already discarded
+```
+
+### fork_timing
+
+```
+Cannot create a fork inside an effect or when state changes are pending
+```
+
 ### get_abort_signal_outside_reaction
 
 ```

documentation/docs/98-reference/.generated/client-errors.md

@@ -1,5 +1,81 @@
 # svelte
 
+## 5.43.2
+
+### Patch Changes
+
+- fix: treat each blocks with async dependencies as uncontrolled ([#17077](https://github.com/sveltejs/svelte/pull/17077))
+
+## 5.43.1
+
+### Patch Changes
+
+- fix: transform `$bindable` after `await` expressions ([#17066](https://github.com/sveltejs/svelte/pull/17066))
+
+## 5.43.0
+
+### Minor Changes
+
+- feat: out-of-order rendering ([#17038](https://github.com/sveltejs/svelte/pull/17038))
+
+### Patch Changes
+
+- fix: settle batch after DOM updates ([#17054](https://github.com/sveltejs/svelte/pull/17054))
+
+## 5.42.3
+
+### Patch Changes
+
+- fix: handle `<svelte:head>` rendered asynchronously ([#17052](https://github.com/sveltejs/svelte/pull/17052))
+
+- fix: don't restore batch in `#await` ([#17051](https://github.com/sveltejs/svelte/pull/17051))
+
+## 5.42.2
+
+### Patch Changes
+
+- fix: better error message for global variable assignments ([#17036](https://github.com/sveltejs/svelte/pull/17036))
+
+- chore: tweak memoizer logic ([#17042](https://github.com/sveltejs/svelte/pull/17042))
+
+## 5.42.1
+
+### Patch Changes
+
+- fix: ignore fork `discard()` after `commit()` ([#17034](https://github.com/sveltejs/svelte/pull/17034))
+
+## 5.42.0
+
+### Minor Changes
+
+- feat: experimental `fork` API ([#17004](https://github.com/sveltejs/svelte/pull/17004))
+
+### Patch Changes
+
+- fix: always allow `setContext` before first await in component ([#17031](https://github.com/sveltejs/svelte/pull/17031))
+
+- fix: less confusing names for inspect errors ([#17026](https://github.com/sveltejs/svelte/pull/17026))
+
+## 5.41.4
+
+### Patch Changes
+
+- fix: take into account static blocks when determining transition locality ([#17018](https://github.com/sveltejs/svelte/pull/17018))
+
+- fix: coordinate mount of snippets with await expressions ([#17021](https://github.com/sveltejs/svelte/pull/17021))
+
+- fix: better optimization of await expressions ([#17025](https://github.com/sveltejs/svelte/pull/17025))
+
+- fix: flush pending changes after rendering `failed` snippet ([#16995](https://github.com/sveltejs/svelte/pull/16995))
+
+## 5.41.3
+
+### Patch Changes
+
+- chore: exclude vite optimized deps from stack traces ([#17008](https://github.com/sveltejs/svelte/pull/17008))
+
+- perf: skip repeatedly traversing the same derived ([#17016](https://github.com/sveltejs/svelte/pull/17016))
+
 ## 5.41.2
 
 ### Patch Changes

packages/svelte/CHANGELOG.md

@@ -100,6 +100,10 @@ $effect(() => {
 
 Often when encountering this issue, the value in question shouldn't be state (for example, if you are pushing to a `logs` array in an effect, make `logs` a normal array rather than `$state([])`). In the rare cases where you really _do_ need to write to state in an effect — [which you should avoid]($effect#When-not-to-use-$effect) — you can read the state with [untrack](svelte#untrack) to avoid adding it as a dependency.
 
+## experimental_async_fork
+
+> Cannot use `fork(...)` unless the `experimental.async` compiler option is `true`
+
 ## flush_sync_in_effect
 
 > Cannot use `flushSync` inside an effect
@@ -108,6 +112,14 @@ The `flushSync()` function can be used to flush any pending effects synchronousl
 
 This restriction only applies when using the `experimental.async` option, which will be active by default in Svelte 6.
 
+## fork_discarded
+
+> Cannot commit a fork that was already discarded
+
+## fork_timing
+
+> Cannot create a fork inside an effect or when state changes are pending
+
 ## get_abort_signal_outside_reaction
 
 > `getAbortSignal()` can only be called inside an effect or derived

packages/svelte/messages/client-errors/errors.md

@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.41.2",
+  "version": "5.43.2",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {

packages/svelte/package.json

@@ -9,11 +9,10 @@ import { decode_character_references } from '../utils/html.js';
 import * as e from '../../../errors.js';
 import * as w from '../../../warnings.js';
 import { create_fragment } from '../utils/create.js';
-import { create_attribute, create_expression_metadata, is_element_node } from '../../nodes.js';
+import { create_attribute, ExpressionMetadata, is_element_node } from '../../nodes.js';
 import { get_attribute_expression, is_expression_attribute } from '../../../utils/ast.js';
 import { closing_tag_omitted } from '../../../../html-tree-validation.js';
 import { list } from '../../../utils/string.js';
-import { regex_whitespace } from '../../patterns.js';
 
 const regex_invalid_unquoted_attribute_value = /^(\/>|[\s"'=<>`])/;
 const regex_closing_textarea_tag = /^<\/textarea(\s[^>]*)?>/i;
@@ -297,7 +296,7 @@ export default function element(parser) {
 			element.tag = get_attribute_expression(definition);
 		}
 
-		element.metadata.expression = create_expression_metadata();
+		element.metadata.expression = new ExpressionMetadata();
 	}
 
 	if (is_top_level_script_or_style) {
@@ -508,7 +507,7 @@ function read_attribute(parser) {
 				end: parser.index,
 				expression,
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			};
 
@@ -528,7 +527,7 @@ function read_attribute(parser) {
 				end: parser.index,
 				expression,
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			};
 
@@ -568,7 +567,7 @@ function read_attribute(parser) {
 					name
 				},
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			};
 
@@ -628,7 +627,7 @@ function read_attribute(parser) {
 				modifiers: /** @type {Array<'important'>} */ (modifiers),
 				value,
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			};
 		}
@@ -658,7 +657,7 @@ function read_attribute(parser) {
 			name: directive_name,
 			expression,
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		};
 
@@ -824,7 +823,7 @@ function read_sequence(parser, done, location) {
 				end: parser.index,
 				expression,
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			};
 

packages/svelte/src/compiler/phases/1-parse/state/element.js

@@ -3,7 +3,7 @@
 /** @import { Parser } from '../index.js' */
 import { walk } from 'zimmerframe';
 import * as e from '../../../errors.js';
-import { create_expression_metadata } from '../../nodes.js';
+import { ExpressionMetadata } from '../../nodes.js';
 import { parse_expression_at } from '../acorn.js';
 import read_pattern from '../read/context.js';
 import read_expression, { get_loose_identifier } from '../read/expression.js';
@@ -42,7 +42,7 @@ export default function tag(parser) {
 		end: parser.index,
 		expression,
 		metadata: {
-			expression: create_expression_metadata()
+			expression: new ExpressionMetadata()
 		}
 	});
 }
@@ -65,7 +65,7 @@ function open(parser) {
 			consequent: create_fragment(),
 			alternate: null,
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		});
 
@@ -249,7 +249,7 @@ function open(parser) {
 			then: null,
 			catch: null,
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		});
 
@@ -334,7 +334,7 @@ function open(parser) {
 			expression,
 			fragment: create_fragment(),
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		});
 
@@ -477,7 +477,7 @@ function next(parser) {
 				consequent: create_fragment(),
 				alternate: null,
 				metadata: {
-					expression: create_expression_metadata()
+					expression: new ExpressionMetadata()
 				}
 			});
 
@@ -643,7 +643,7 @@ function special(parser) {
 			end: parser.index,
 			expression,
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		});
 
@@ -721,7 +721,7 @@ function special(parser) {
 				end: parser.index - 1
 			},
 			metadata: {
-				expression: create_expression_metadata()
+				expression: new ExpressionMetadata()
 			}
 		});
 	}
@@ -748,7 +748,7 @@ function special(parser) {
 			end: parser.index,
 			expression: /** @type {AST.RenderTag['expression']} */ (expression),
 			metadata: {
-				expression: create_expression_metadata(),
+				expression: new ExpressionMetadata(),
 				dynamic: false,
 				arguments: [],
 				path: [],