[docs] Update demos to TypeScript

[OnkelTem]

• The issue is present in the latest release (v.3)
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

Project cannot be compiled due to a TS error.

Expected Behavior 🤔

No error.

Steps to Reproduce 🕹

https://codesandbox.io/s/autumn-pond-6n2p7?file=/src/App.tsx

As you may see, there are errors in the 14, 22 and 29 lines.
They don't prevent project from running on that sandbox, but locally it fails to build.

TypeScript error in .../my-app/src/App.tsx(15,9):
Type 'Dispatch<SetStateAction<Date | null>>' is not assignable to type '(date: MaterialUiPickersDate) => void'.
  Types of parameters 'value' and 'date' are incompatible.
    Type 'MaterialUiPickersDate' is not assignable to type 'SetStateAction<Date | null>'.
      Type 'Moment' is not assignable to type 'SetStateAction<Date | null>'.
        Type 'Moment' is missing the following properties from type 'Date': toDateString, toTimeString, toLocaleDateString, toLocaleTimeString, and 35 more.  TS2322

    13 |         inputVariant="outlined"
    14 |         value={selectedDate}
  > 15 |         onChange={handleDateChange}
       |         ^
    16 |       />
    17 | 
    18 |       <DateTimePicker

I followed the installation guide and opted to moment.js as the utils lib:

npm i @date-io/moment@1.x moment

Context 🔦

I try to get the first example from the docs working, to understand how it's assumed to be used at all.

Your Environment 🌎

Tech	Version
@material-ui/core	v4.11.0
@material-ui/pickers	v3.2.10
React	^16.9.0
Browser
TypeScript
etc.

[oliviertassinari]

@OnkelTem Thanks for the feedback. We do no longer support v3, we would encourage you to have a look at https://next.material-ui-pickers.dev/.

Also, I think that we can use this as an opportunity to update all the demos to TypeScript (once we move the source into the main repo, we will get the JavaScript version automatically generated.

[dmtrKovalenko]

I think here is a conflict between date-fns and moment adapter. It is actually the same problem as described here https://next.material-ui-pickers.dev/guides/typescript#important-note-on-type-inference

Actually we need not to only update demos, but also autogenerate demos for different adapters

[oliviertassinari]

but also autogenerate demos for different adapters

Linking #1650 as related.

[OnkelTem]

@oliviertassinari

Good, I'm gonna try the next version then.

[OnkelTem]

Switched to the version 4.x (4.0.0-alpha.9) and right away I get an error:

import { LocalizationProvider } from '@material-ui/pickers';

// pick an adapter for your date library
import MomentUtils from '@material-ui/pickers/adapter/moment';

// ...

<LocalizationProvider dateAdapter={ MomentUtils }>
                      ^^^^^^^^^^^

TS2322: Type 'typeof MomentUtils' is not assignable to type 'new (...args: any) => MuiPickersAdapter<unknown>'.
   Type 'MomentUtils' is missing the following properties from type 'IUtils<unknown>': yearFormat, yearMonthFormat, dateTime12hFormat, dateTime24hFormat, and 12 more.

  LocalizationProvider.d.ts(6, 5): The expected type comes from property 'dateAdapter' which is declared here on type 'IntrinsicAttributes & LocalizationProviderProps & { children?: ReactNode; }'

Ideas?
Should I create a new ticket?

[OnkelTem]

Omg, folks, that was not reliable: I couldn't reproduce the previous problem in a new clean project.

Ignore everything from below (I forgot to type useState())

But instead, I could reproduce the initial problem, but now - with 4.x branch.

Checkout this sandbox: https://codesandbox.io/s/pickers-next-onchange-rqpvq?file=/src/App.tsx

<DatePicker
        value={selectedDate}
        onChange={handleDateChange}
        ^^^^^^^^
        renderInput={props => <TextField {...props} />}
      />

As you see there's that same error another error, but again - with onChange:

(JSX attribute) BasePickerProps<ParsableDate<React.SetStateAction<Date>>, Date | ((prevState: Date) => Date) | null>.onChange: (date: Date | ((prevState: Date) => Date) | null, keyboardInputValue?: string | undefined) => void
onChange callback @DateIOType.

Type 'Dispatch<SetStateAction<Date>>' is not assignable to type '(date: Date | ((prevState: Date) => Date) | null, keyboardInputValue?: string | undefined) => void'.
  Types of parameters 'value' and 'date' are incompatible.
    Type 'Date | ((prevState: Date) => Date) | null' is not assignable to type 'SetStateAction<Date>'.
      Type 'null' is not assignable to type 'SetStateAction<Date>'.ts(2322)
BasePicker.d.ts(11, 5): The expected type comes from property 'onChange' which is declared here on type 'IntrinsicAttributes & BaseDatePickerProps & Pick<ResponsiveWrapperProps, "displayStaticWrapperAs" | ... 11 more ... | "desktopModeMediaQuery"> & BasePickerProps<...> & Pick<...> & WithDateAdapterProps<...> & RefAttributes<...>'

[oliviertassinari]

@OnkelTem Well, this confusion is IMHO a good argument as to why we need to bring TypeScript demos (#1990) and isolated demos (#1650) that can open in CodeSandbox. This alone, I think will be a significant differentiator with the alternative React date pickers.

As a developer, when you are evaluating different options, you have limited time to experiment with each of them.

[OnkelTem]

There's also one problem with the pickers in WebStorm. The DatePicker properties are not resolved.

Usually one can Ctrl-click on any property of a component and get into its definition. With DatePicker (and DateTimePicker) all its properties are not clickable and forcing Ctrl-click on any of them brings an error hint: Cannot find declaration to go to.
It's not the case however with LocalizationProvider.

Any ideas?

[oliviertassinari]

Which version are you using? Do you have a reproduction with codesandbox 4.0.0-alpha.9?

[OnkelTem]

@oliviertassinari No, I cannot reproduce the problem with properties not being resolved in CodeSandbox. I can create a ticket however in the WebStorm issue queue about this problem.

Also, I think it's worth trying the same in VS Code.

[oliviertassinari]

@OnkelTem Cool, in this case, we can ignore it. Let's focus on updating all the demos to TypeScript, this increases the TypeScript test coverage at the same time than helping new users.

[oliviertassinari]

It was fixed in https://next.material-ui.com/components/pickers/.