Sync svelte docs (#903)

sync svelte docs

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

apps/svelte.dev/content/docs/svelte/05-special-elements/01-svelte-boundary.md

@@ -0,0 +1,79 @@
+---
+title: <svelte:boundary>
+---
+
+```svelte
+<svelte:boundary onerror={handler}>...</svelte:boundary>
+```
+
+Boundaries allow you to guard against errors in part of your app from breaking the app as a whole, and to recover from those errors.
+
+If an error occurs while rendering or updating the children of a `<svelte:boundary>`, or running any [`$effect`]($effect) functions contained therein, the contents will be removed.
+
+Errors occurring outside the rendering process (for example, in event handlers) are _not_ caught by error boundaries.
+
+## Properties
+
+For the boundary to do anything, one or both of `failed` and `onerror` must be provided.
+
+### `failed`
+
+If an `failed` snippet is provided, it will be rendered with the error that was thrown, and a `reset` function that recreates the contents ([demo](/playground/hello-world#H4sIAAAAAAAAE3VRy26DMBD8lS2tFCIh6JkAUlWp39Cq9EBg06CAbdlLArL87zWGKk8ORnhmd3ZnrD1WtOjFXqKO2BDGW96xqpBD5gXerm5QefG39mgQY9EIWHxueRMinLosti0UPsJLzggZKTeilLWgLGc51a3gkuCjKQ7DO7cXZotgJ3kLqzC6hmex1SZnSXTWYHcrj8LJjWTk0PHoZ8VqIdCOKayPykcpuQxAokJaG1dGybYj4gw4K5u6PKTasSbjXKgnIDlA8VvUdo-pzonraBY2bsH7HAl78mKSHZpgIcuHjq9jXSpZSLixRlveKYQUXhQVhL6GPobXAAb7BbNeyvNUs4qfRg3OnELLj5hqH9eQZqCnoBwR9lYcQxuVXeBzc8kMF8yXY4yNJ5oGiUzP_aaf_waTRGJib5_Ad3P_vbCuaYxzeNpbU0eUMPAOKh7Yw1YErgtoXyuYlPLzc10_xo_5A91zkQL_AgAA)):
+
+```svelte
+<svelte:boundary>
+	<FlakyComponent />
+
+	{#snippet failed(error, reset)}
+		<button onclick={reset}>oops! try again</button>
+	{/snippet}
+</svelte:boundary>
+```
+
+> [!NOTE]
+> As with [snippets passed to components](snippet#Passing-snippets-to-components), the `failed` snippet can be passed explicitly as a property...
+>
+> ```svelte
+> <svelte:boundary {failed}>...</svelte:boundary>
+> ```
+>
+> ...or implicitly by declaring it directly inside the boundary, as in the example above.
+
+### `onerror`
+
+If an `onerror` function is provided, it will be called with the same two `error` and `reset` arguments. This is useful for tracking the error with an error reporting service...
+
+```svelte
+<svelte:boundary onerror={(e) => report(e)}>
+	...
+</svelte:boundary>
+```
+
+...or using `error` and `reset` outside the boundary itself:
+
+```svelte
+<script>
+	let error = $state(null);
+	let reset = $state(() => {});
+
+	function onerror(e, r) {
+		error = e;
+		reset = r;
+	}
+</script>
+
+<svelte:boundary {onerror}>
+	<FlakyComponent />
+</svelte:boundary>
+
+{#if error}
+	<button onclick={() => {
+		error = null;
+		reset();
+	}}>
+		oops! try again
+	</button>
+{/if}
+```
+
+If an error occurs inside the `onerror` function (or if you rethrow the error), it will be handled by a parent boundary if such exists.

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

@@ -762,6 +762,18 @@ A component can have a single top-level `<style>` element
 `<svelte:body>` does not support non-event attributes or spread attributes
 ```
 
+### svelte_boundary_invalid_attribute
+
+```
+Valid attributes on `<svelte:boundary>` are `onerror` and `failed`
+```
+
+### svelte_boundary_invalid_attribute_value
+
+```
+Attribute value must be a non-string expression
+```
+
 ### svelte_component_invalid_this
 
 ```

apps/svelte.dev/content/docs/svelte/98-reference/21-svelte-compiler.md

@@ -445,6 +445,11 @@ namespace AST {
 		name: 'svelte:fragment';
 	}
 
+	export interface SvelteBoundary extends BaseElement {
+		type: 'SvelteBoundary';
+		name: 'svelte:boundary';
+	}
+
 	export interface SvelteHead extends BaseElement {
 		type: 'SvelteHead';
 		name: 'svelte:head';

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

@@ -766,6 +766,18 @@ A component can have a single top-level `<style>` element
 `<svelte:body>` does not support non-event attributes or spread attributes
 ```
 
+### svelte_boundary_invalid_attribute
+
+```
+Valid attributes on `<svelte:boundary>` are `onerror` and `failed`
+```
+
+### svelte_boundary_invalid_attribute_value
+
+```
+Attribute value must be a non-string expression
+```
+
 ### svelte_component_invalid_this
 
 ```