fix: remount at any hydration error (#16248)

* fix: remount at any hydration error

* re-throw svelte error immediately

* log error as warn

* fix?

Author: 7nik

.changeset/hip-eagles-yawn.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: remount at any hydration error

packages/svelte/src/internal/client/render.js

@@ -136,20 +136,28 @@ export function hydrate(component, options) {
 
 		return /**  @type {Exports} */ (instance);
 	} catch (error) {
-		if (error === HYDRATION_ERROR) {
-			if (options.recover === false) {
-				e.hydration_failed();
-			}
-
-			// If an error occured above, the operations might not yet have been initialised.
-			init_operations();
-			clear_text_content(target);
+		// re-throw Svelte errors - they are certainly not related to hydration
+		if (
+			error instanceof Error &&
+			error.message.split('\n').some((line) => line.startsWith('https://svelte.dev/e/'))
+		) {
+			throw error;
+		}
+		if (error !== HYDRATION_ERROR) {
+			// eslint-disable-next-line no-console
+			console.warn('Failed to hydrate: ', error);
+		}
 
-			set_hydrating(false);
-			return mount(component, options);
+		if (options.recover === false) {
+			e.hydration_failed();
 		}
 
-		throw error;
+		// If an error occured above, the operations might not yet have been initialised.
+		init_operations();
+		clear_text_content(target);
+
+		set_hydrating(false);
+		return mount(component, options);
 	} finally {
 		set_hydrating(was_hydrating);
 		set_hydrate_node(previous_hydrate_node);

packages/svelte/tests/hydration/samples/whitespace-at-block-start/Nested.svelte

@@ -0,0 +1 @@
+<p>nested</p>

packages/svelte/tests/hydration/samples/whitespace-at-block-start/_config.js

@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	errors: [
+		'Failed to hydrate: ',
+		new DOMException("Node can't be inserted in a #text parent.", 'HierarchyRequestError')
+	]
+});

packages/svelte/tests/hydration/samples/whitespace-at-block-start/_expected.html

@@ -0,0 +1 @@
+<main><p>nested</p><!----></main>

packages/svelte/tests/hydration/samples/whitespace-at-block-start/_override.html

@@ -0,0 +1,2 @@
+<!--[-->
+<main><p>nested</p><!----></main><!--]-->

packages/svelte/tests/hydration/samples/whitespace-at-block-start/main.svelte

@@ -0,0 +1,7 @@
+<script>
+	import Nested from './Nested.svelte';
+</script>
+
+<main>
+	<Nested />
+</main>