From a280ec439b353514e4ada100ee50548d856ecedc Mon Sep 17 00:00:00 2001
From: Aditya Singh <adisin650@gmail.com>
Date: Sun, 24 May 2026 05:34:14 -0700
Subject: [PATCH] Ignore undefined style values on native

---
 .../src/native/css/processStyle.js               |  8 ++++++++
 .../tests/css/css-create-test.native.js          | 16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/packages/react-strict-dom/src/native/css/processStyle.js b/packages/react-strict-dom/src/native/css/processStyle.js
index 7329436f..754d338b 100644
--- a/packages/react-strict-dom/src/native/css/processStyle.js
+++ b/packages/react-strict-dom/src/native/css/processStyle.js
@@ -73,6 +73,14 @@ export function processStyle(
   for (const propName in style) {
     const styleValue = style[propName];
 
+    // Drop "undefined" values so they don't reach the underlying style
+    // resolver, which only accepts strings, numbers, objects or null. This
+    // mirrors web behavior, where undefined values are ignored, and lets
+    // inline style functions return undefined to opt out of a property.
+    if (styleValue === undefined) {
+      continue;
+    }
+
     if (skipValidation !== true && !isAllowedStyleKey(propName)) {
       if (__DEV__) {
         warnMsg(`unsupported style property "${propName}"`);
diff --git a/packages/react-strict-dom/tests/css/css-create-test.native.js b/packages/react-strict-dom/tests/css/css-create-test.native.js
index 2067238f..73910dfa 100644
--- a/packages/react-strict-dom/tests/css/css-create-test.native.js
+++ b/packages/react-strict-dom/tests/css/css-create-test.native.js
@@ -2102,6 +2102,22 @@ describe('css.create()', () => {
       });
       expect(root.toJSON().props.style).toMatchSnapshot();
     });
+
+    test('undefined values are ignored', () => {
+      const styles = css.create({
+        root: (gap) => ({
+          rowGap: gap
+        })
+      });
+      let root;
+      act(() => {
+        root = create(<html.div style={styles.root(undefined)} />);
+      });
+      const { style } = root.toJSON().props;
+      // The property is dropped rather than passed through as undefined,
+      // which would otherwise be rejected by the style resolver.
+      expect(Object.prototype.hasOwnProperty.call(style, 'rowGap')).toBe(false);
+    });
   });
 
   /**