[Popover] function for `slotProps.paper` isn't working

[jedwards1211]

Steps to reproduce

Link to live example: (required)

Steps:

1. Click the "Open Popovers" button
2. Popovers should appear above and below the button
3. Note that the popover above (which uses object slotProps.paper) has a red background
4. Note that the popover above (which uses function slotProps.paper) has a white background

Current behavior

The popover passed a function for slotProps.paper doesn't have the same appearance as the one with an object for slotProps.paper

Expected behavior

Both popovers have the same background color from slotProps.paper

Context

I was trying to accommodate these changes in MUI in material-ui-popup-state, and a user reported this issue: jcoreio/material-ui-popup-state#134

Your environment

npx @mui/envinfo

  Browser: Chrome 124.0.6367.207
  System:
    OS: macOS 14.4.1
  Binaries:
    Node: 20.10.0 - ~/.nvm/versions/node/v20.10.0/bin/node
    npm: 10.2.3 - ~/.nvm/versions/node/v20.10.0/bin/npm
    pnpm: 8.11.0 - ~/.nvm/versions/node/v20.10.0/bin/pnpm
  Browsers:
    Chrome: 124.0.6367.209
    Edge: Not Found
    Safari: 17.4.1
  npmPackages:
    @emotion/react: ^11.10.5 => 11.10.5 
    @emotion/styled: ^11.10.5 => 11.10.5 
    @mui/icons-material: ^5.10.16 => 5.10.16 
    @mui/material: ^5.15.18 => 5.15.18 
    @mui/styles: 5.15.14 => 5.15.14 
    @mui/types: ^7.2.2 => 7.2.2 
    @types/react: ^18.0.26 => 18.0.26 
    react: ^18.2.0 => 18.2.0 
    react-dom: ^18.2.0 => 18.2.0 
    typescript: ^5.1.0 => 5.4.2 

Search keywords: popover,slot-props

[mnajdova]

Thanks for the report, looks like we missed handling function for the slotProps.paper, e.g. I see https://github.com/mui/material-ui/blob/next/packages/mui-material/src/Popover/Popover.js#L128. @DiegoAndai can you please check this?

[DiegoAndai]

Thanks for the report, @jedwards1211; I accepted it as a bug.
As the Popover is not using the useSlot hook, it's missing the callback functionality.
Ready to take it if anyone wants to work on it. Added it to #40417.