Add Fragment to @stencil/core

[NEO97online]

Stencil version:

 @stencil/core@0.13.2

I'm submitting a:

[ ] bug report
[x] feature request
[ ] support request => Please do not submit support requests here, use one of these channels: https://stencil-worldwide.herokuapp.com/ or https://forum.ionicframework.com/

Current behavior:
Rendering multiple elements requires either a wrapping div or returning an array. Returning an array avoids rendering an unwanted <div>, but array format with JSX is hard to read and work with, especially in larger components.

Expected behavior:
Just like React, you could wrap multiple elements in a <Fragment> tag.

Steps to reproduce:
Without fragment:

render() {
  return [
    <div>My first element</div>,
    <div>
        <span>Another element</span>
    </div>,
    <div>And another</div>
  ]
}

Related code:
With fragment:

render() {
  return (
    <Fragment>
      <div>My first element</div>
      <div>
        <span>Another element</span>
      </div>
      <div>And another</div>
    </Fragment>
  )
}

Other information:

This is an extremely simple feature to add, I'm just not sure where it should go in the stencil repository.
The working Fragment code is literally just this one line:

export const Fragment = (props, children) => children

Or without ES6:

export function Fragment(props, children) {
  return children
}

Used as a JSX element, this simply renders the children without rendering an arbitrary wrapping element.

I made a package here to provide this feature, but it would be fantastic if it were available in @stencil/core. People coming from React will love this.

If someone can advise me where in the repo to add this code, I would be happy to make the PR myself.

[simonhaenisch]

But web components need a dash in the tag name, so maybe it should be called ion-fragment 🤓

Edit: Uhm sorry I somehow thought this was an issue in the ionic repo 🙈

[NEO97online]

@simonhaenisch Yeah, this isn't a web component, it's just a JSX tag! So, no dash.

[manucorporat]

@michaelauderer we would like to be able to use the short-syntax:

<>

</>

but looks like it's not supported by typescript outside React, "React" is hardcoded into typescript: microsoft/TypeScript#20469

[NEO97online]

@manucorporat Yes, this would be even nicer, but until we get support from typescript it would be great to at least include the Fragment element. <Fragment> is still commonly used in React anyways so it would make sense to have this. It could be a long time before Typescript supports the short-syntax.

[o-t-w]

Is there any update on this? Not having full control over markup is a pretty drastic limitation. Particularly now with CSS grid, markup structure matters for layout and I can't just have unnecessary divs around everything. Pretty sure LitElement doesn't have this drawback.

[simonhaenisch]

@o-t-w not sure what you mean because this doesn't limit your ability to have full control over your markup? It's just syntactic sugar (that indeed increases readability a lot), i. e. you can already either use arrays or add the suggested Fragment functional component into your project.

[NEO97online]

@o-t-w For now, I've already built a solution for it here: https://github.com/michaelauderer/stencil-fragment

If someone can point out where it belongs in the Stencil repository, I'll make a PR. (@manucorporat, any thoughts?)

[manucorporat]

Stencil 1.0 introduces a new <Host> exported from @stencil/core that can act as a Fragment!

[liron-navon]

@manucorporat
I found this super confusing,<Host> is nothing like react <Fragment>,

Error: The <Host> must be the single root component. Make sure:
- You are NOT using hostData() and <Host> in the same component.
- <Host> is used once, and it's the single root component of the render() function.

[sfmskywalker]

I, too would like to see<Fragment> be part of StencilJS. My use case is that I have a modular web component where consumers of the component can declare plugins, tat themselves render widgets. These renderings are either JSX (Vdom objects) or string values (in case the consumer is a vanilla JS app with no JSX support). When the widget is rendered as string, I need to set the innerHTML property of a containing element. Ideally, without having to use a <div>.

Kudos to @auderer for providing exactly that!

[sfmskywalker]

Looks like I celebrated too soon. I misunderstood Fragment to also have an InnerHTML property somehow causing that content to magically be rendered. Instead, it looks like it's just a container that renders child elements. It makes sense that it doesn't do what I expected with InnerHTML.