From 7b2854ee75b3814206981c437b919bab8239c0f9 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Thu, 22 Aug 2024 20:43:31 +0100
Subject: [PATCH] fix: correctly hydrate empty raw blocks

---
 .changeset/shiny-wombats-argue.md                 |  5 +++++
 .../svelte/src/internal/client/dom/blocks/html.js | 11 ++++++++---
 .../tests/hydration/samples/raw-empty/_config.js  | 15 +++++++++++++++
 .../tests/hydration/samples/raw-empty/main.svelte |  1 +
 4 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/shiny-wombats-argue.md
 create mode 100644 packages/svelte/tests/hydration/samples/raw-empty/_config.js
 create mode 100644 packages/svelte/tests/hydration/samples/raw-empty/main.svelte

diff --git a/.changeset/shiny-wombats-argue.md b/.changeset/shiny-wombats-argue.md
new file mode 100644
index 0000000000..b35f1cf304
--- /dev/null
+++ b/.changeset/shiny-wombats-argue.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly hydrate empty raw blocks
diff --git a/packages/svelte/src/internal/client/dom/blocks/html.js b/packages/svelte/src/internal/client/dom/blocks/html.js
index cdfa1baa71..26d29e015d 100644
--- a/packages/svelte/src/internal/client/dom/blocks/html.js
+++ b/packages/svelte/src/internal/client/dom/blocks/html.js
@@ -46,15 +46,20 @@ export function html(node, get_value, svg, mathml, skip_warning) {
 
 	var value = '';
 
-	/** @type {Effect | null} */
+	/** @type {Effect | undefined} */
 	var effect;
 
 	block(() => {
-		if (value === (value = get_value())) return;
+		if (value === (value = get_value())) {
+			if (hydrating) {
+				hydrate_next();
+			}
+			return;
+		}
 
 		if (effect) {
 			destroy_effect(effect);
-			effect = null;
+			effect = undefined;
 		}
 
 		if (value === '') return;
diff --git a/packages/svelte/tests/hydration/samples/raw-empty/_config.js b/packages/svelte/tests/hydration/samples/raw-empty/_config.js
new file mode 100644
index 0000000000..21b9f0e386
--- /dev/null
+++ b/packages/svelte/tests/hydration/samples/raw-empty/_config.js
@@ -0,0 +1,15 @@
+import { test } from '../../test';
+
+export default test({
+	server_props: {
+		html: '<div></div>'
+	},
+
+	props: {
+		html: '<div></div>'
+	},
+
+	test(assert, target) {
+		assert.htmlEqual(target.innerHTML, '<div></div>');
+	},
+});
diff --git a/packages/svelte/tests/hydration/samples/raw-empty/main.svelte b/packages/svelte/tests/hydration/samples/raw-empty/main.svelte
new file mode 100644
index 0000000000..c7ff3d05c9
--- /dev/null
+++ b/packages/svelte/tests/hydration/samples/raw-empty/main.svelte
@@ -0,0 +1 @@
+<div>{@html ''}</div>