TypeScript typings for render(props.children) should be ComponentChild[], not ComponentChildren

Since preact makes the very useful guarantee that, in the render function, props.children will always be an array, typing the props as RenderableProps<P> gives the overly-broad type for the children property of ComponentChildren. This used to be just ComponentChild[], but has now been extended significantly (I believe to improve tsx support).

For example:

render(props:RenderableProps<MyProps>) {
   if(props.children.length) {  <= FAIL

You have to do the rather ugly:

render(props:RenderableProps<MyProps>) {
    if((props.children as ComponentChild[]).length) {

instead, to encode the assertion that we know that .children is guaranteed to be an array in the render function.

[Alexendoo]

Oh is that to say a TS change wouldn’t be needed in that case @marvinhagemeister? That is kind of relieving since I was finding it difficult to model the preact behaviour.

I think I agree with you on the children front too, in practise most components I write rarely have an opinion about the type of children passed to it

[timpur]

+ 1

I tried this and had issues using ComponentChild[] but think your on the right idea

Also to add shouldn’t render be able to return props.children ? thus render: ComponentChildren