use React Fragment instead of as prop

[alzalabany]

Feature Request

react now support a container that doesnot render a div for itself. aka 'React.Fragment or <> for babel7'

Problem description

when we use "props.as" to select type of child to render, example in something like

<Transition.Group as={List} duration={200} divided size='huge' verticalAlign='middle'>
          {items.map(item => (
            <List.Item key={item}>
              <Image avatar src={`/images/avatar/small/${item}.jpg`} />
              <List.Content header={_.startCase(item)} />
            </List.Item>
          ))}
</Transition.Group>

• its very hard to tell now what props are set for Transition.Group and which are intended for List component that i passed in props.as.
• name colliissino can happen easily especially when i pass cutom components to 'as' example if i pass a component that needs a size prop.

Proposed solution

can be used without as prop, and we just update render function removing uneeded code.

// https://github.com/Semantic-Org/Semantic-UI-React/blob/master/src/modules/Transition/TransitionGroup.js
render() {
    debug('render')
    debug('props', this.props)
    debug('state', this.state)

    const { children } = this.state
    //- const ElementType = getElementType(TransitionGroup, this.props)
    //- const rest = getUnhandledProps(TransitionGroup, this.props)

    //- return <ElementType {...rest}>{_.values(children)}</ElementType>
    return <React.Fragment> {_.values(children)} </React.Fragment>
 }

now

• i don't need to polute and do un-needed calcs.
• this is much cleaner cause i dont have to polute my TransitionGroup in this example with props intended for child component

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[layershifter]

Fragments are supported only from 16.2 while currently we require 16.0. The next breaking changes will require 16.3, #2844.

We will don't remove as prop there, for me it's a cool solution and it's a part our API. I've made a PR that sets as defaults to Fragment, see #3032.

Now, you can use Fragments, too:

<Transition.Group as={React.Fragment} />