DatagridInput imports

[megantaylor]

I'm using the latest and greatest react-admin release, but have been getting this message in the console for a while:

./node_modules/ra-ui-materialui/dist/esm/input/DatagridInput.js:118:32
"export 'InputHelperText' was not found in '../../../../..'
  116 |             React.createElement(Datagrid, __assign({}, rest)),
  117 |             pagination !== false && pagination,
> 118 |             React.createElement(InputHelperText, { touched: fieldState.isTouched || formState.isSubmitted, error: (_a = fieldState.error) === null || _a === void 0 ? void 0 : _a.message }))));
      |                                ^
  119 | };
  120 | 

I think that this import is incorrect:

import {
    CommonInputProps,
    InputHelperText,
    SupportCreateSuggestionOptions,
} from '.';

and perhaps should be this instead:

import { SupportCreateSuggestionOptions } from './useSupportCreateSuggestion';
import { CommonInputProps } from './CommonInputProps';
import { InputHelperText } from './InputHelperText';

[fzaninotto]

Weird, we don't have this error when using the component in the storybook. Could you please build a reproduction using the simple example CodeSandbox?

https://codesandbox.io/s/github/marmelab/react-admin/tree/master/examples/simple

[megantaylor]

i cant make a repro in codesandbox, i guess it could be an issue with webpack version or config. would you accept a PR with this change?