DX: Refine useEndpoint generic

[nnelgxorz]

What is it?

• Feature / enhancement
• Bug
• Docs / tests

Description

Currently it is hard to type your useEndpoint call to your endpoint function.

Consider we have an onGet defined as an EndpointHandler<string>

Current behavior:

const onGet: EndpointHandler<string> = () => {
  return "Oh Qwik..."
}
const resource = useEndpoint(); // ResourceReturn<unknown>
const resource = useEndpoint<typeof onGet>(); // ResourceReturn<EndpointHandler<string>
const resource = useEndpoint<ReturnType<typeof onGet>>(); // ResouceReturn<string|void|null|undefined|Promise<string|void|null|undefined>>

Of course, you could type it yourself, ie useEndpoint<string>, but any changes to the return type of onGet do not trigger a type error for useEndpoint, making it a brittle solution. Also, you have the option of incorrectly type your useEndpoint call and not receiving an error until runtime. 😬

By adding a little helper type to the useEndpoint definition, we can check the generic, and if T extends EndpointHandler, extract the EndpointHandler type, otherwise use the original T type.

This allows developers to pass the relatively terse useEndpoint<typeof onGet>() and receive proper typing.

This gives the following behavior:

const onGet: EndpointHandler<string> = () => {
  return "Yay Qwik!"
}
const resource = useEndpoint(); // ResourceReturn<unknown>
const resource = useEndpoint<boolean>(); // ResourceReturn<boolean>
const resource = useEndpoint<null>(); // ResourceReturn<null>
//...etc
const resource = useEndpoint<typeof onGet>(); // ResourceReturn<string>

Checklist:

• My code follows the developer guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• Added new tests to cover the fix / functionality

[manucorporat]

Thanks a lot for the PR!! love it!