fix: ensure input value is correctly set during hydration

.changeset/moody-toys-relax.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: ensure input value is correctly set during hydration

packages/svelte/src/internal/client/dom/elements/attributes.js

@@ -29,10 +29,12 @@ export function remove_input_attr_defaults(dom) {
 		const remove_defaults = () => {
 			if (already_removed) return;
 			already_removed = true;
-			const value = dom.getAttribute('value');
+			debugger;
+			const value_attribute = dom.getAttribute('value');
+			const value = dom.value;
 			set_attribute(dom, 'value', null);
 			set_attribute(dom, 'checked', null);
-			if (value) dom.value = value;
+			if (value_attribute) dom.value = value;
 		};
 		// @ts-expect-error
 		dom.__on_r = remove_defaults;
@@ -50,6 +52,7 @@ export function set_value(element, value) {
 	var attributes = (element.__attributes ??= {});
 
 	if (attributes.value === (attributes.value = value)) return;
+	debugger;
 	// @ts-expect-error
 	element.value = value;
 }

packages/svelte/tests/runtime-runes/samples/hydrate-modified-input-2/_config.js

@@ -0,0 +1,14 @@
+import { test } from '../../test';
+
+export default test({
+	skip_mode: ['client'],
+
+	async test({ assert, target, hydrate }) {
+		// @ts-ignore
+		window.is_browser = true;
+		hydrate();
+		assert.htmlEqual(target.innerHTML, '<input type="text">');
+		const input = /** @type {HTMLInputElement} */ (target.querySelector('input'));
+		assert.htmlEqual(input.value, 'browser');
+	}
+});

packages/svelte/tests/runtime-runes/samples/hydrate-modified-input-2/main.svelte

@@ -0,0 +1,6 @@
+<script>
+	// @ts-ignore
+	let value = window.is_browser ? 'browser' : 'server';
+</script>
+
+<input type="text" {value} />