export PureComponent

[Shelob9]

Description

I added an export for React.PureComponent and a test to prove its exported as a function. #8118

How has this been tested?

I wrote a unit test to prove element.PureComponent is a function.

Checklist:

• [ x] My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards. Not applicable
• My code has proper inline documentation.

[gziolo]

We provide pure higher-order component (HOC) which plays the same role but uses slightly modified implementation:
https://github.com/WordPress/gutenberg/blob/master/packages/compose/src/pure/index.js

It's also worth to mention that it is baked in into withDispatch HOC, so you might be using it already, but you weren't aware of it :)

I think @aduth or @youknowriad can give a more detailed explanation to the topic.

[youknowriad]

Yes, pure is basically the same thing written as a Higher-order component instead. I think it's slightly more flexible. Related discussion in the original PR #6313