I am exploring the creation of a type-safe API-SDK where each entity supports different API endpoints based on an enum. In this scenario, only two out of three entities allow posting. Although calling the post-function with a known type resolves correctly, looping over all the endpoints supporting post introduces an unexpected return type void, which poses challenges when passing it to other functions that do not accept void. The example provided below illustrates this issue. How can I eliminate the void return type from the post-function or replace it with never?
enum Entity {
Person,
Organization,
Job,
}
interface Person {}
interface Organization {}
const entityEndpointsSupportingPost= [Entity.Person, Entity.Organization];
type EntityEndpointsSupportingPost = {
[Entity.Person]: Person;
[Entity.Organization]: Organization;
[Entity.Job]: void;
}
async function postEntity<T extends keyof EntityEndpointsSupportingPost>(endpoint: T): Promise<EntityEndpointsSupportingPost[T]> {
const result = await fetch(`api/${endpoint}`);
return await result.json();
}
const person = Entity.Person;
// The type here is recognized as Promise<Person>
const postedPerson = postEntity(person);
for (const entity of entityEndpointsSupportingPost) {
// The type in this loop becomes Promise<void | Person | Organization>
const postedEntity = postEntity(entity);
}