[DatePicker] Remove helperText default value, document it

Steps to reproduce

function App() {
  const [value, setValue] = React.useState(null);

  return (
    <LocalizationProvider dateAdapter={DateFnsUtils}>
      <DatePicker
        value={value}
        onChange={newValue => {
          setValue(newValue);
        }}
        renderInput={props => <TextField {...props} />}
      />
    </LocalizationProvider>
  );
}

https://codesandbox.io/s/condescending-hoover-m5jk7?file=/index.js:234-580

Expected behavior

Should the helperText have a value by default? It feels strange. I think that we should remove it to:

1. reduce duplication of information: placeholder + input mask should be good enough.
2. reduce the height of the input takes by default. It might not fit into people’s layout.
3. encourage the usage of the helper text for related information regarding the field.

Actual behavior

Environment

Tech	Version
@material-ui/lab	v5.0.0-alpha.16

[dmtrKovalenko]

There is an option. Pass helperText={null}

[taschetto]

I’m experimenting with 4.0.0-alpha.7 and it’s very good. I understand the purpose on showing the format by default, but my users are all on the same locale and we have a pretty strong date format default. So the helperText with the format is undesirable. +1 for at least having an option to disable.

EDIT:

Also I use the Textfield helperText prop to show validation messages from others sources (like async validations from the server) and the picker forcing it doesn’t allow me to do that anymore.

Thus I think the helperText should be managed by the developer and not by the lib.