From 6ca0c71fcda15981c3bb0c4b664a3cd2b3158dbf Mon Sep 17 00:00:00 2001
From: adiguba <frederic.martini@gmail.com>
Date: Fri, 7 Feb 2025 21:10:08 +0100
Subject: [PATCH 1/4] set value/checked by JS

---
 .../svelte/src/internal/client/dom/elements/attributes.js     | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index eab27e6c02d5..0bdc4c772acd 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -387,10 +387,14 @@ export function set_attributes(
 						let prev = input.defaultValue;
 						input.removeAttribute(name);
 						input.defaultValue = prev;
+						input.value = '';
+						// @ts-ignore
+						input.__value = null;
 					} else {
 						let prev = input.defaultChecked;
 						input.removeAttribute(name);
 						input.defaultChecked = prev;
+						input.checked = false;
 					}
 				} else {
 					element.removeAttribute(key);

From 47b99143eea9252eff5ba9a9a18b687c763b6ee5 Mon Sep 17 00:00:00 2001
From: adiguba <frederic.martini@gmail.com>
Date: Fri, 7 Feb 2025 21:29:26 +0100
Subject: [PATCH 2/4] test

---
 .../samples/attribute-spread-input/_config.js | 33 +++++++++++++++++++
 .../attribute-spread-input/main.svelte        | 22 +++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 packages/svelte/tests/runtime-runes/samples/attribute-spread-input/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/attribute-spread-input/main.svelte

diff --git a/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/_config.js b/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/_config.js
new file mode 100644
index 000000000000..ab941255037e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/_config.js
@@ -0,0 +1,33 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ target, assert }) {
+		// Test for https://github.com/sveltejs/svelte/issues/15237
+		const [setValues, clearValue] = target.querySelectorAll('button');
+		const [text1, text2, check1, check2] = target.querySelectorAll('input');
+
+		assert.equal(text1.value, '');
+		assert.equal(text2.value, '');
+		assert.equal(check1.checked, false);
+		assert.equal(check2.checked, false);
+
+		flushSync(() => {
+			setValues.click();
+		});
+
+		assert.equal(text1.value, 'message');
+		assert.equal(text2.value, 'message');
+		assert.equal(check1.checked, true);
+		assert.equal(check2.checked, true);
+
+		flushSync(() => {
+			clearValue.click();
+		});
+
+		assert.equal(text1.value, '');
+		assert.equal(text2.value, '');
+		assert.equal(check1.checked, false);
+		assert.equal(check2.checked, false);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/main.svelte b/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/main.svelte
new file mode 100644
index 000000000000..4bb4365ee270
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/attribute-spread-input/main.svelte
@@ -0,0 +1,22 @@
+<script>
+	let value = $state();
+	let checked = $state(false);
+
+	function setValues() {
+		value = 'message';
+		checked = true;
+	}
+	function clearValues() {
+		value = null;
+		checked = null;
+	}
+</script>
+
+<button onclick={setValues}>setValues</button>
+<button onclick={clearValues}>clearValues</button>
+
+<input type="text" {value} />
+<input type="text" {value} {...{}} />
+
+<input type="checkbox" {checked} />
+<input type="checkbox" {checked} {...{}} />

From 577a8637e051415d73810e3ffd004dc0d1f5ea21 Mon Sep 17 00:00:00 2001
From: adiguba <frederic.martini@gmail.com>
Date: Fri, 7 Feb 2025 21:34:13 +0100
Subject: [PATCH 3/4] changeset

---
 .changeset/fuzzy-zoos-repeat.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/fuzzy-zoos-repeat.md

diff --git a/.changeset/fuzzy-zoos-repeat.md b/.changeset/fuzzy-zoos-repeat.md
new file mode 100644
index 000000000000..3fb3f0502e57
--- /dev/null
+++ b/.changeset/fuzzy-zoos-repeat.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: value/checked not correctly set using spread

From 0531f279c50306462903379930e14b7ecd66b3c4 Mon Sep 17 00:00:00 2001
From: adiguba <frederic.martini@gmail.com>
Date: Fri, 7 Feb 2025 22:37:30 +0100
Subject: [PATCH 4/4] fix test form-default-value-spread

---
 .../internal/client/dom/elements/attributes.js    | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index 0bdc4c772acd..21f347729c48 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -382,19 +382,18 @@ export function set_attributes(
 				if (name === 'value' || name === 'checked') {
 					// removing value/checked also removes defaultValue/defaultChecked — preserve
 					let input = /** @type {HTMLInputElement} */ (element);
-
+					const use_default = prev === undefined;
 					if (name === 'value') {
-						let prev = input.defaultValue;
+						let previous = input.defaultValue;
 						input.removeAttribute(name);
-						input.defaultValue = prev;
-						input.value = '';
+						input.defaultValue = previous;
 						// @ts-ignore
-						input.__value = null;
+						input.value = input.__value = use_default ? previous : null;
 					} else {
-						let prev = input.defaultChecked;
+						let previous = input.defaultChecked;
 						input.removeAttribute(name);
-						input.defaultChecked = prev;
-						input.checked = false;
+						input.defaultChecked = previous;
+						input.checked = use_default ? previous : false;
 					}
 				} else {
 					element.removeAttribute(key);