[Menu] Popover CSS API is not available

[cherniavskii]

• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

It is possible to override styles of Popover inside Menu.

Current Behavior

It is not possible to override styles of Popover inside Menu.

Steps to Reproduce (for bugs)

N/A

Context

Menu intercepts classes prop, so it is not passed to Popover component along with ...other props.
My suggestion would be adding PopoverProps, which then can be used to pass classes prop to Popover (like it is implemented in Drawer).
I can submit a PR if you are OK with this solution

Your Environment

N/A

[oliviertassinari]

There is only one style in the Popover component. You can already access it with the PaperProps property. Still, it doesn't merge the classNames, I think that it should. Fixing that issue should answer your use cases. I'm not sure about adding a PopoverProps as it's already the root component. I feel like PopoverClasses would be more appropriate.

[oliviertassinari]

Here is the same pattern already implemented:
https://github.com/callemall/material-ui/blob/4de0c54b111328f68bb2e9ff1931ae2e79646566/src/Input/InputLabel.js#L132