Sync svelte docs (#1065)

sync svelte docs

Co-authored-by: Rich-Harris <[email protected]>

Author: github-actions[bot]

apps/svelte.dev/content/docs/svelte/03-template-syntax/16-class.md

@@ -0,0 +1,91 @@
+---
+NOTE: do not edit this file, it is generated in apps/svelte.dev/scripts/sync-docs/index.ts
+title: class
+---
+
+There are two ways to set classes on elements: the `class` attribute, and the `class:` directive.
+
+## Attributes
+
+Primitive values are treated like any other attribute:
+
+```svelte
+<div class={large ? 'large' : 'small'}>...</div>
+```
+
+> [!NOTE]
+> For historical reasons, falsy values (like `false` and `NaN`) are stringified (`class="false"`), though `class={undefined}` (or `null`) cause the attribute to be omitted altogether. In a future version of Svelte, all falsy values will cause `class` to be omitted.
+
+### Objects and arrays
+
+Since Svelte 5.16, `class` can be an object or array, and is converted to a string using [clsx](https://github.com/lukeed/clsx).
+
+If the value is an object, the truthy keys are added:
+
+```svelte
+<script>
+	let { cool } = $props();
+</script>
+
+<!-- results in `class="cool"` if `cool` is truthy,
+     `class="lame"` otherwise -->
+<div class={{ cool, lame: !cool }}>...</div>
+```
+
+If the value is an array, the truthy values are combined:
+
+```svelte
+<!-- if `faded` and `large` are both truthy, results in
+     `class="saturate-0 opacity-50 scale-200"` -->
+<div class={[faded && 'saturate-0 opacity-50', large && 'scale-200']}>...</div>
+```
+
+Note that whether we're using the array or object form, we can set multiple classes simultaneously with a single condition, which is particularly useful if you're using things like Tailwind.
+
+Arrays can contain arrays and objects, and clsx will flatten them. This is useful for combining local classes with props, for example:
+
+```svelte
+<!--- file: Button.svelte --->
+<script>
+	let props = $props();
+</script>
+
+<button {...props} class={['cool-button', props.class]}>
+	{@render props.children?.()}
+</button>
+```
+
+The user of this component has the same flexibility to use a mixture of objects, arrays and strings:
+
+```svelte
+<!--- file: App.svelte --->
+<script>
+	import Button from './Button.svelte';
+	let useTailwind = $state(false);
+</script>
+
+<Button
+	onclick={() => useTailwind = true}
+	class={{ 'bg-blue-700 sm:w-1/2': useTailwind }}
+>
+	Accept the inevitability of Tailwind
+</Button>
+```
+
+## The `class:` directive
+
+Prior to Svelte 5.16, the `class:` directive was the most convenient way to set classes on elements conditionally.
+
+```svelte
+<!-- These are equivalent -->
+<div class={{ cool, lame: !cool }}>...</div>
+<div class:cool={cool} class:lame={!cool}>...</div>
+```
+
+As with other directives, we can use a shorthand when the name of the class coincides with the value:
+
+```svelte
+<div class:cool class:lame={!cool}>...</div>
+```
+
+> [!NOTE] Unless you're using an older version of Svelte, consider avoiding `class:`, since the attribute is more powerful and composable.

apps/svelte.dev/content/docs/svelte/03-template-syntax/18-class.md

@@ -21,15 +21,19 @@ A component is attempting to bind to a non-bindable property `%key%` belonging t
 ### component_api_changed
 
 ```
-%parent% called `%method%` on an instance of %component%, which is no longer valid in Svelte 5. See https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes for more information
+%parent% called `%method%` on an instance of %component%, which is no longer valid in Svelte 5
 ```
 
+See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more information.
+
 ### component_api_invalid_new
 
 ```
-Attempted to instantiate %component% with `new %name%`, which is no longer valid in Svelte 5. If this component is not under your control, set the `compatibility.componentApi` compiler option to `4` to keep it working. See https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes for more information
+Attempted to instantiate %component% with `new %name%`, which is no longer valid in Svelte 5. If this component is not under your control, set the `compatibility.componentApi` compiler option to `4` to keep it working.
 ```
 
+See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more information.
+
 ### derived_references_self
 
 ```

apps/svelte.dev/content/docs/svelte/98-reference/.generated/client-errors.md

@@ -52,7 +52,7 @@ Your `console.%method%` contained `$state` proxies. Consider using `$inspect(...
 
 When logging a [proxy](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy), browser devtools will log the proxy itself rather than the value it represents. In the case of Svelte, the 'target' of a `$state` proxy might not resemble its current value, which can be confusing.
 
-The easiest way to log a value as it changes over time is to use the [`$inspect`](https://svelte.dev/docs/svelte/$inspect) rune. Alternatively, to log things on a one-off basis (for example, inside an event handler) you can use [`$state.snapshot`](https://svelte.dev/docs/svelte/$state#$state.snapshot) to take a snapshot of the current value.
+The easiest way to log a value as it changes over time is to use the [`$inspect`](/docs/svelte/$inspect) rune. Alternatively, to log things on a one-off basis (for example, inside an event handler) you can use [`$state.snapshot`](/docs/svelte/$state#$state.snapshot) to take a snapshot of the current value.
 
 ### event_handler_invalid
 

apps/svelte.dev/content/docs/svelte/98-reference/.generated/client-warnings.md

@@ -62,7 +62,7 @@ Enforce that `autofocus` is not used on elements. Autofocusing elements can caus
 ### a11y_click_events_have_key_events
 
 ```
-Visible, non-interactive elements with a click event must be accompanied by a keyboard event handler. Consider whether an interactive element such as `<button type="button">` or `<a>` might be more appropriate. See https://svelte.dev/docs/accessibility-warnings#a11y-click-events-have-key-events for more details
+Visible, non-interactive elements with a click event must be accompanied by a keyboard event handler. Consider whether an interactive element such as `<button type="button">` or `<a>` might be more appropriate
 ```
 
 Enforce that visible, non-interactive elements with an `onclick` event are accompanied by a keyboard event handler.

apps/svelte.dev/content/docs/svelte/98-reference/.generated/compile-warnings.md

@@ -80,7 +80,7 @@ constructor(options: ComponentConstructorOptions<Properties<Props, Slots>>);
 
 - <span class="tag deprecated">deprecated</span> This constructor only exists when using the `asClassComponent` compatibility helper, which
 is a stop-gap solution. Migrate towards using `mount` instead. See
-[migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more info.
+[migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more info.
 
 </div>
 
@@ -98,7 +98,7 @@ $destroy(): void;
 <div class="ts-block-property-bullets">
 
 - <span class="tag deprecated">deprecated</span> This method only exists when using one of the legacy compatibility helpers, which
-is a stop-gap solution. See [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
+is a stop-gap solution. See [migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
 for more info.
 
 </div>
@@ -120,7 +120,7 @@ $on<K extends Extract<keyof Events, string>>(
 <div class="ts-block-property-bullets">
 
 - <span class="tag deprecated">deprecated</span> This method only exists when using one of the legacy compatibility helpers, which
-is a stop-gap solution. See [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
+is a stop-gap solution. See [migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
 for more info.
 
 </div>
@@ -139,7 +139,7 @@ $set(props: Partial<Props>): void;
 <div class="ts-block-property-bullets">
 
 - <span class="tag deprecated">deprecated</span> This method only exists when using one of the legacy compatibility helpers, which
-is a stop-gap solution. See [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
+is a stop-gap solution. See [migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
 for more info.
 
 </div>
@@ -576,13 +576,13 @@ interface Component<
 ): {
 	/**
 	 * @deprecated This method only exists when using one of the legacy compatibility helpers, which
-	 * is a stop-gap solution. See [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
+	 * is a stop-gap solution. See [migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
 	 * for more info.
 	 */
 	$on?(type: string, callback: (e: any) => void): () => void;
 	/**
 	 * @deprecated This method only exists when using one of the legacy compatibility helpers, which
-	 * is a stop-gap solution. See [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
+	 * is a stop-gap solution. See [migration guide](https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes)
 	 * for more info.
 	 */
 	$set?(props: Partial<Props>): void;

apps/svelte.dev/content/docs/svelte/98-reference/20-svelte.md

@@ -83,7 +83,7 @@ Enforce that `autofocus` is not used on elements. Autofocusing elements can caus
 ### a11y_click_events_have_key_events
 
 ```
-Visible, non-interactive elements with a click event must be accompanied by a keyboard event handler. Consider whether an interactive element such as `<button type="button">` or `<a>` might be more appropriate. See https://svelte.dev/docs/accessibility-warnings#a11y-click-events-have-key-events for more details
+Visible, non-interactive elements with a click event must be accompanied by a keyboard event handler. Consider whether an interactive element such as `<button type="button">` or `<a>` might be more appropriate
 ```
 
 Enforce that visible, non-interactive elements with an `onclick` event are accompanied by a keyboard event handler.

apps/svelte.dev/content/docs/svelte/98-reference/30-compiler-warnings.md

@@ -28,15 +28,19 @@ A component is attempting to bind to a non-bindable property `%key%` belonging t
 ### component_api_changed
 
 ```
-%parent% called `%method%` on an instance of %component%, which is no longer valid in Svelte 5. See https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes for more information
+%parent% called `%method%` on an instance of %component%, which is no longer valid in Svelte 5
 ```
 
+See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more information.
+
 ### component_api_invalid_new
 
 ```
-Attempted to instantiate %component% with `new %name%`, which is no longer valid in Svelte 5. If this component is not under your control, set the `compatibility.componentApi` compiler option to `4` to keep it working. See https://svelte.dev/docs/svelte/v5-migration-guide#Components-are-no-longer-classes for more information
+Attempted to instantiate %component% with `new %name%`, which is no longer valid in Svelte 5. If this component is not under your control, set the `compatibility.componentApi` compiler option to `4` to keep it working.
 ```
 
+See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-longer-classes) for more information.
+
 ### derived_references_self
 
 ```

apps/svelte.dev/content/docs/svelte/98-reference/30-runtime-errors.md

@@ -59,7 +59,7 @@ Your `console.%method%` contained `$state` proxies. Consider using `$inspect(...
 
 When logging a [proxy](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy), browser devtools will log the proxy itself rather than the value it represents. In the case of Svelte, the 'target' of a `$state` proxy might not resemble its current value, which can be confusing.
 
-The easiest way to log a value as it changes over time is to use the [`$inspect`](https://svelte.dev/docs/svelte/$inspect) rune. Alternatively, to log things on a one-off basis (for example, inside an event handler) you can use [`$state.snapshot`](https://svelte.dev/docs/svelte/$state#$state.snapshot) to take a snapshot of the current value.
+The easiest way to log a value as it changes over time is to use the [`$inspect`](/docs/svelte/$inspect) rune. Alternatively, to log things on a one-off basis (for example, inside an event handler) you can use [`$state.snapshot`](/docs/svelte/$state#$state.snapshot) to take a snapshot of the current value.
 
 ### event_handler_invalid