Fix: Datepicker: Unable to enter date manually

[chuyler]

Fixes #2956

Additional description

Previously, the DatePicker would try to format the value in the input box after every keystroke, preventing the user from actually typing out a date or changing an existing date by pressing the delete key in front of a character and replacing it with a new character. Additionally, passing in a new date value to the component did not update the value displayed in the input box.

This fix includes changes for:

• Initialization of input state variables has been moved to getDerivedStateFromProps to allow updates from parent component
• handleInputChange no longer calls parent onChange callback but instead waits until user presses ENTER or TAB
• Pressing ESCAPE from within the input box resets the component to initial state

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[interactivellama]

Hi, I'm back from the dead!

This patterns appears to stop the Datepicker from being controlled by the state of the parent component and moves state into the Datepicker.

I could be missing something in the above statement, but components should be controlled components instead of uncontrolled per the project overview. https://github.com/salesforce/design-system-react/blob/master/docs/codebase-overview.md#use-controlled-components

[chuyler]

I'm not sure I follow your comment. Please go to current demo page for Date Picker.
https://react.lightningdesignsystem.com/components/date-pickers/

Let's say you don't want to use the widget to navigate to a date but instead you know the exact date and format you would like to type in. Click on the input box and start typing. You will find that the second you enter a number the picker widget closes and the box auto-completes to a date you didn't intend to enter.

If you have a better solution that would allow users to enter the date using the keyboard manually I would gladly review it.

[chuyler]

@interactivellama Could you provide an update on this? I'd really like to get this merged. If you have a better solution I'm all ears.

[anujsingla]

@interactivellama Could you please review this MR? We are also facing the same issue in our project