[swipeable drawer] External ref causes mergeSlotProps to overwrite internal ref

[juraj-muravsky]

Steps to reproduce

Steps:

1. Open this live example: https://stackblitz.com/edit/ob1sd6fc-ta22ng51?file=src%2FDemo.tsx
2. Open the preview in a touch-enabled device or enable touch emulation in DevTools
3. Click either "Open Test 1" or "Open Test 2" button to open either drawer
4. Attempt to close the drawer by swiping (touch drag gesture)

Current behavior

The application crashes with the following error:
Uncaught TypeError: Cannot read properties of undefined (reading 'contains')

Expected behavior

The drawer closes

Context

From testing, this happens because mergeSlotProps does not correctly handle the callback ref returned by useForkRef, and will overwrite it with the external ref if present.

Your environment

npx @mui/envinfo

  System:
    OS: Windows 11 10.0.26100
  Binaries:
    Node: 20.19.5 - C:\nvm4w\nodejs\node.EXE
    npm: 10.8.2 - C:\nvm4w\nodejs\npm.CMD
    pnpm: Not Found
  Browsers:
    Chrome: 135.0.7049.42
  npmPackages:
    @emotion/react: ^11.14.0 => 11.14.0
    @emotion/styled: ^11.14.1 => 11.14.1
    @mui/core-downloads-tracker:  7.3.9
    @mui/lab: 7.0.1-beta.22 => 7.0.1-beta.22
    @mui/material: ^7.3.9 => 7.3.9
    @mui/private-theming:  7.3.9
    @mui/styled-engine:  7.3.9
    @mui/system:  7.3.9
    @mui/types:  7.4.12
    @mui/utils:  7.3.9
    @mui/x-date-pickers: ^7.29.4 => 7.29.4
    @mui/x-internals:  7.29.0
    @types/react: ^19.2.14 => 19.2.14
    react: ^19.2.4 => 19.2.4
    react-dom: ^19.2.4 => 19.2.4
    typescript: ^5.9.3 => 5.9.3

Search keywords: mergeSlotProps SwipeableDrawer paper ref

[linear]

MAT-1795

[mj12albert]

@juraj-muravsky Would you mind checking if it's fixed in this canary version: https://stackblitz.com/edit/ob1sd6fc-26pqvjgx

A workaround is to pass a custom component to slotProps.paper.component that forwards ref and merges your ref which bypasses the issue:

import * as React from 'react';
import SwipeableDrawer from '@mui/material/SwipeableDrawer';
import useForkRef from '@mui/material/utils/useForkRef';

const userPaperRef = React.createRef<HTMLDivElement>();

const SwipeablePaperRoot = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElement>>(
  function SwipeablePaperRoot(props, ref) {
    const mergedRef = useForkRef(ref, userPaperRef);
    return <div {...props} ref={mergedRef} />;
  },
);

<SwipeableDrawer
  open
  onOpen={() => {}}
  onClose={() => {}}
  slotProps={{ paper: { component: SwipeablePaperRoot } }}
/>;

https://stackblitz.com/edit/ob1sd6fc-26pqvjgx?file=src%2FDemo.tsx