JSX Children Tuple with single element

[plusgut]

Search Terms:
When A single element is given as a Child, it is not handled as an Array.

Code

const Component = (props: { children: [ JSX.Element ] }) => props.children;

const test = <Component><element /></Component>; // Should not throw an error

Expected behavior:
There should not be a completely different behaviour from TypeScript when a single Child is present in a Tuple.

Actual behavior:
The following error is thrown: This JSX tag's 'children' prop expects type '[Element]' which requires multiple children, but only a single child was provided

I am aware that React behaves that way, but the JSX-Language states that everything between JSXOpeningElement and JSXSelfClosingElement are JSXChildren. https://github.com/facebook/jsx

[RyanCavanaugh]

{ children: [ JSX.Element ] } is basically an impossible contract to satisfy.

I don't understand what you expect to happen here. Your function says that this code is legal:

const Component = (props: { children: [ JSX.Element ] }) => props.children.slice(0);

const test = <Component><element /></Component>; // Should not throw an error

But that code is going to throw an error at runtime. Why should something that manifestly defies the specified types pass the type checking?

[weswigham]

FYI: Impossible in react (for now - children is apparently supposed to be opaque and subject to change), but fully possible (probable, even) in other JSX frameworks. This is a place where we have some unfortunate react-unique logic baked in, since, AFAIK, at the time we didn't even have tuple types but still wanted to allow validation against singular children?

[plusgut]

@RyanCavanaugh
It would throw a runtime error in react, but not necessarily in other frameworks.
And especially when we look at the jsx specifications itself, React is doing it wrong.

@weswigham Exactly! Don't you agree that there should be the option, to opt-out of these react-specific things?

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.