[TextField] unable to specify inputClassName and apply props to input element

[kgregory]

While answering a question on StackOverflow I ran into an issue:

In order to pass props to the input element via the TextField component, you need to specify an inputProps object within the InputProps property. This is fine, except for the fact that the current implementation of TextField sets its own value for inputProps so that the inputClassName is applied to the input element.

By handing your own value of inputProps to TextField, you will overwrite the value applied by TextField, leaving inputClassName unset.

As of today, the only way to use both is to include inputClassName in the inner inputProps object.

Expected Behavior

inputClassName should be applied to the input element whether InputProps includes inputProps or not. The one exception would be if the inner inputProps includes a className prop as well.

Current Behavior

If you specify inputClassName and include inputProps within InputProps, the class will not be applied to the input element.

Steps to Reproduce (for bugs)

See this codesandbox for a reproduction of this issue

[oliviertassinari]

It's related to #9326. cc @rosskevin