From 18699ba2eed9cad80cec85840c888bb6584b04dc Mon Sep 17 00:00:00 2001
From: 7nik <kifiranet@gmail.com>
Date: Sat, 2 Aug 2025 20:46:58 +0300
Subject: [PATCH] fix: reset attribute cache after setting corresponding
 property

---
 .changeset/afraid-carrots-study.md            |  5 +++++
 .../client/dom/elements/attributes.js         |  4 +++-
 .../attribute-after-property/_config.js       | 19 +++++++++++++++++++
 .../attribute-after-property/main.svelte      |  6 ++++++
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/afraid-carrots-study.md
 create mode 100644 packages/svelte/tests/runtime-legacy/samples/attribute-after-property/_config.js
 create mode 100644 packages/svelte/tests/runtime-legacy/samples/attribute-after-property/main.svelte

diff --git a/.changeset/afraid-carrots-study.md b/.changeset/afraid-carrots-study.md
new file mode 100644
index 000000000000..71f4232edb85
--- /dev/null
+++ b/.changeset/afraid-carrots-study.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: reset attribute cache after setting corresponding property
diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index 22e532f5e44a..2fa5d4541c48 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -19,7 +19,7 @@ import { attach } from './attachments.js';
 import { clsx } from '../../../shared/attributes.js';
 import { set_class } from './class.js';
 import { set_style } from './style.js';
-import { ATTACHMENT_KEY, NAMESPACE_HTML } from '../../../../constants.js';
+import { ATTACHMENT_KEY, NAMESPACE_HTML, UNINITIALIZED } from '../../../../constants.js';
 import { block, branch, destroy_effect, effect } from '../../reactivity/effects.js';
 import { init_select, select_option } from './bindings/select.js';
 import { flatten } from '../../reactivity/async.js';
@@ -446,6 +446,8 @@ export function set_attributes(element, prev, next, css_hash, skip_warning = fal
 			) {
 				// @ts-ignore
 				element[name] = value;
+				// remove it from attributes's cache
+				if (name in attributes) attributes[name] = UNINITIALIZED;
 			} else if (typeof value !== 'function') {
 				set_attribute(element, name, value, skip_warning);
 			}
diff --git a/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/_config.js b/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/_config.js
new file mode 100644
index 000000000000..f6a98b1797c7
--- /dev/null
+++ b/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/_config.js
@@ -0,0 +1,19 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	test({ target, assert }) {
+		const input = target.querySelector('input');
+		const button = target.querySelector('button');
+
+		assert.equal(input?.step, 'any');
+
+		button?.click();
+		flushSync();
+		assert.equal(input?.step, '10');
+
+		button?.click();
+		flushSync();
+		assert.equal(input?.step, 'any');
+	}
+});
diff --git a/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/main.svelte b/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/main.svelte
new file mode 100644
index 000000000000..2921e4e24182
--- /dev/null
+++ b/packages/svelte/tests/runtime-legacy/samples/attribute-after-property/main.svelte
@@ -0,0 +1,6 @@
+<script>
+    let step = "any";
+</script>
+
+<input type="range" {...{step}} />
+<button onclick={() => step = step === "any" ? 10 : "any"}>change step</button>
\ No newline at end of file