Bug: cloneElement does not correctly merge styles when used in nested components

[User6531]

Description:

I encountered an issue when using React.cloneElement in two separate components that wrap an SVG icon. When both components use cloneElement, the styles from the first wrapper are lost in the second wrapper.

Steps to Reproduce:

1. IconResizer applies width, height, and flexShrink styles.
2. IconColorizer applies color: #FFC700.
3. When both are used together, only the styles from IconResizer remain, and the color is not applied.

Code Example:

import React, { cloneElement, ReactElement } from 'react';

const IconResizer = ({ children }: { children: ReactElement }) => {
  return cloneElement(children, {
    style: { height: '16px', width: '16px', flexShrink: 0 },
  });
};

const IconColorizer = ({ children }: { children: ReactElement }) => {
  return cloneElement(children, {
    style: { ...(children.props.style || {}), color: '#FFC700' },
  });
};

const MyIcon = () => (
  <IconResizer>
    <IconColorizer>
      <svg
        width="24"
        height="24"
        viewBox="0 0 24 24"
        fill="none"
        xmlns="http://www.w3.org/2000/svg"
      >
        <path
          d="M14.0001 24C13.7837 24..."
          fill="currentColor"
        />
      </svg>
    </IconColorizer>
  </IconResizer>
);

export default MyIcon;

---

Expected Behavior:

The svg element should have both height: 16px, width: 16px, flexShrink: 0 and color: #FFC700 applied.

Actual Behavior:

• The height and width from IconResizer are applied correctly.
• The color from IconColorizer is missing.

---

Environment:

• React version: 18.3.1
• Browser: chrome

---

Possible Cause:

It seems that the second cloneElement is not properly merging the styles from the first cloneElement. This behavior is unexpected, as cloneElement is supposed to preserve existing props while overriding the specified ones.

---

Additional Notes:

• If I manually spread the styles when creating the first cloneElement, the issue persists.
• Using a single cloneElement works fine, but nesting them causes the first one's styles to be lost.

Would appreciate insights on whether this is expected behavior or a bug. Thanks!

[alex-r-bigelow]

Not a react dev, but Google sent me here for a similar issue.

Took me a while to figure out, but React passes in the merged style to your component as its style prop. IconColorizer needs to use the merged style prop that React is giving it, not try to look for already-merged props on the child:

Per the docs:

Cloning an element does not modify the original element.

Fixed code

(I made a few changes for typescript / multiple children / React 19 reasons, as I was using your example to debug my own; thank you!)

import {
  Children,
  cloneElement,
  CSSProperties,
  isValidElement,
  ReactElement,
} from 'react';

const IconResizer = ({
  children,
}: {
  children: ReactElement<SVGElement> | ReactElement<SVGElement>[];
}) => {
  return (
    <>
      {Children.map(children, (child) => {
        if (!isValidElement(child)) {
          return;
        }
        return cloneElement(child, {
          style: {
            ...(child.props.style || {}),
            height: '16px',
            width: '16px',
            flexShrink: '0',
          } as CSSStyleDeclaration,
        });
      })}
    </>
  );
};

const IconColorizer = ({
  children,
  style,
}: {
  children: ReactElement<SVGElement> | ReactElement<SVGElement>[];
  style?: CSSProperties;
}) => {
  return (
    <>
      {Children.map(children, (child) => {
        if (!isValidElement(child)) {
          return;
        }
        return cloneElement(child, {
          style: {
            ...(style || {}),
            color: '#FFC700',
          } as CSSStyleDeclaration,
        });
      })}
    </>
  );
};

export const MyIcon = () => (
  <IconResizer>
    <IconColorizer>
      <svg
        width="24"
        height="24"
        viewBox="0 0 24 24"
        fill="none"
        xmlns="http://www.w3.org/2000/svg"
      >
        <path d="M0 0 L24 24 L0 24 Z" fill="currentColor" />
      </svg>
    </IconColorizer>
  </IconResizer>
);

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