Reintroduce Hidden component

[GDownes]

Reintroduce the hidden component.

https://material-ui.com/components/hidden/

The removal of the hidden compatibility breaks backwards compatibility.
Currently the sx property makes it difficult to replicate the functionally of the hidden component.
I think it has been prematurely removed.

For example:

<Hidden smDown><Button display='flex' /><Hidden/>

becomes,

<Button sx={{ display: { xs: "none", sm: "none", md: "flex", lg: "flex", xl: "flex" }}} />

Having to list all the breakpoints in the example above isn't ideal. Hidden supported this use case well.

[mnajdova]

@GDownes you don't need to specify all breakpoints, see https://github.com/mui-org/material-ui/pull/26348/files Does this clarify things?

-<Hidden implementation="css" smDown><Button' /></Hidden>
+<Button sx={{ display: { xs: 'none', sm: 'flex' } }} />

See https://codesandbox.io/s/nifty-banzai-gb6co?file=/index.js

[GDownes]

@mnajdova Thanks for the quick reply:
It's seems I do need to specify all breakpoints:

See: https://codesandbox.io/s/upbeat-rosalind-6ch0t?file=/index.js

In this example I'd expect xs to also be hidden as I've marked a higher breakpoint as hidden but it shows

[mnajdova]

@GDownes it works the other way around, the object in the sx breakpoints specifies up(), that's why you need to specify the lowest breakpoint (xs to be hidden), and the next breakpoint for which you want the component to be shown. On the example you've sent, change sm with xs and it would be hidden for both xs and sm

[GDownes]

@mnajdova Thanks for the clarification. That makes sense, closing. I still think that Hidden should be deprecated more slowly.

[oliviertassinari]

I have stopped listening to issues for the last 3 weeks and will likely continue going forward. I was planning to open the same issue when I realized it was already created. It seems that the removal of the <Hidden> component was premature. We got a lot more people complaining about this one than most of the other BCs.

My main concern is that the migration path is only fully available since v5, people on v4 don't have a smooth transition. I propose we introduce the component back but deprecated. cc @mui-org/core.