merge main

Author: Rich-Harris

.changeset/hip-singers-vanish.md

@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: SSR-safe ID generation with `$props.id()`

.changeset/long-moles-join.md

@@ -199,3 +199,24 @@ You can, of course, separate the type declaration from the annotation:
 > [!NOTE] Interfaces for native DOM elements are provided in the `svelte/elements` module (see [Typing wrapper components](typescript#Typing-wrapper-components))
 
 Adding types is recommended, as it ensures that people using your component can easily discover which props they should provide.
+
+
+## `$props.id()`
+
+This rune, added in version 5.20.0, generates an ID that is unique to the current component instance. When hydrating a server-rendered component, the value will be consistent between server and client.
+
+This is useful for linking elements via attributes like `for` and `aria-labelledby`.
+
+```svelte
+<script>
+	const uid = $props.id();
+</script>
+
+<form>
+	<label for="{uid}-firstname">First Name: </label>
+	<input id="{uid}-firstname" type="text" />
+
+	<label for="{uid}-lastname">Last Name: </label>
+	<input id="{uid}-lastname" type="text" />
+</form>
+```

documentation/docs/02-runes/05-$props.md

@@ -585,7 +585,13 @@ Unrecognised compiler option %keypath%
 ### props_duplicate
 
 ```
-Cannot use `$props()` more than once
+Cannot use `%rune%()` more than once
+```
+
+### props_id_invalid_placement
+
+```
+`$props.id()` can only be used at the top level of components as a variable declaration initializer
 ```
 
 ### props_illegal_name

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

@@ -7,7 +7,7 @@
   "license": "MIT",
   "packageManager": "[email protected]",
   "engines": {
-    "pnpm": "^9.0.0"
+    "pnpm": ">=9.0.0"
   },
   "repository": {
     "type": "git",
@@ -44,6 +44,6 @@
     "typescript": "^5.5.4",
     "typescript-eslint": "^8.2.0",
     "v8-natives": "^1.2.5",
-    "vitest": "^2.0.5"
+    "vitest": "^2.1.9"
   }
 }

package.json

@@ -1,5 +1,31 @@
 # svelte
 
+## 5.19.10
+
+### Patch Changes
+
+- fix: when re-connecting unowned deriveds, remove their unowned flag ([#15255](https://github.com/sveltejs/svelte/pull/15255))
+
+- fix: allow mutation of private derived state ([#15228](https://github.com/sveltejs/svelte/pull/15228))
+
+## 5.19.9
+
+### Patch Changes
+
+- fix: ensure unowned derived dependencies are not duplicated when reactions are skipped ([#15232](https://github.com/sveltejs/svelte/pull/15232))
+
+- fix: hydrate `href` that is part of spread attributes ([#15226](https://github.com/sveltejs/svelte/pull/15226))
+
+## 5.19.8
+
+### Patch Changes
+
+- fix: properly set `value` property of custom elements ([#15206](https://github.com/sveltejs/svelte/pull/15206))
+
+- fix: ensure custom element updates don't run in hydration mode ([#15217](https://github.com/sveltejs/svelte/pull/15217))
+
+- fix: ensure tracking returns true, even if in unowned ([#15214](https://github.com/sveltejs/svelte/pull/15214))
+
 ## 5.19.7
 
 ### Patch Changes

packages/svelte/CHANGELOG.md

@@ -128,7 +128,11 @@ This turned out to be buggy and unpredictable, particularly when working with de
 
 ## props_duplicate
 
-> Cannot use `$props()` more than once
+> Cannot use `%rune%()` more than once
+
+## props_id_invalid_placement
+
+> `$props.id()` can only be used at the top level of components as a variable declaration initializer
 
 ## props_illegal_name
 

packages/svelte/messages/compile-errors/script.md

@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.19.7",
+  "version": "5.19.10",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
@@ -143,7 +143,7 @@
     "source-map": "^0.7.4",
     "tiny-glob": "^0.2.9",
     "typescript": "^5.5.4",
-    "vitest": "^2.0.5"
+    "vitest": "^2.1.9"
   },
   "dependencies": {
     "@ampproject/remapping": "^2.3.0",

packages/svelte/package.json

@@ -339,6 +339,15 @@ declare namespace $effect {
 declare function $props(): any;
 
 declare namespace $props {
+	/**
+	 * Generates an ID that is unique to the current component instance. When hydrating a server-rendered component,
+	 * the value will be consistent between server and client.
+	 *
+	 * This is useful for linking elements via attributes like `for` and `aria-labelledby`.
+	 * @since 5.20.0
+	 */
+	export function id(): string;
+
 	// prevent intellisense from being unhelpful
 	/** @deprecated */
 	export const apply: never;

packages/svelte/src/ambient.d.ts

@@ -297,12 +297,22 @@ export function module_illegal_default_export(node) {
 }
 
 /**
- * Cannot use `$props()` more than once
+ * Cannot use `%rune%()` more than once
+ * @param {null | number | NodeLike} node
+ * @param {string} rune
+ * @returns {never}
+ */
+export function props_duplicate(node, rune) {
+	e(node, 'props_duplicate', `Cannot use \`${rune}()\` more than once\nhttps://svelte.dev/e/props_duplicate`);
+}
+
+/**
+ * `$props.id()` can only be used at the top level of components as a variable declaration initializer
  * @param {null | number | NodeLike} node
  * @returns {never}
  */
-export function props_duplicate(node) {
-	e(node, 'props_duplicate', `Cannot use \`$props()\` more than once\nhttps://svelte.dev/e/props_duplicate`);
+export function props_id_invalid_placement(node) {
+	e(node, 'props_id_invalid_placement', `\`$props.id()\` can only be used at the top level of components as a variable declaration initializer\nhttps://svelte.dev/e/props_id_invalid_placement`);
 }
 
 /**