[material-ui] mergeSlotProps doesn't handle functions

[DiegoAndai]

Steps to reproduce

Steps:

1. Open this link to live example: https://stackblitz.com/edit/stackblitz-starters-gh8zdjcb?file=src%2FApp.tsx
2. Click the button
3. See how only one of the functions is called

Current behavior

Only one of the functions is called

Expected behavior

Both of the functions should be called

Context

Discovered in #45210 (comment)

Your environment

npx @mui/envinfo

  System:
    OS: macOS 14.5
  Binaries:
    Node: 22.2.0 - ~/.nvm/versions/node/v22.2.0/bin/node
    npm: 10.7.0 - ~/.nvm/versions/node/v22.2.0/bin/npm
    pnpm: 9.15.4 - ~/.nvm/versions/node/v22.2.0/bin/pnpm
  Browsers:
    Chrome: 134.0.6998.44
    Edge: 133.0.3065.92
    Safari: 17.5
  npmPackages:
    @mui/internal-docs-utils: workspace:^ => 2.0.0 
    @mui/internal-scripts: workspace:^ => 2.0.3 
    @mui/internal-test-utils: workspace:^ => 2.0.3 
    @mui/joy: workspace:* => 5.0.0-beta.49 
    @mui/material: workspace:^ => 7.0.0-beta.2 
    @mui/utils: workspace:^ => 7.0.0-beta.2 
    @pigment-css/react: 0.0.30 => 0.0.30 
    @types/react: ^19.0.10 => 19.0.10 
    typescript: ^5.7.3 => 5.7.3 

Search keywords: mergeSlotProps functions slotprops slots

[mnajdova]

In a generic function like this, wouldn't it make sense to compose the event handlers and make the other functions replace the existing ones? Btw, there is similar utility in Base UI, maybe we can take the logic from there?

[siriwatknp]

In a generic function like this, wouldn't it make sense to compose the event handlers and make the other functions replace the existing ones? Btw, there is similar utility in Base UI, maybe we can take the logic from there?

True, make sense to follow Base UI.