useSubmit doesn't work with TypeScript interfaces because it needs an index signature

[szszoke]

Hello,

I am trying to use the useSubmit hook to submit an object and encode it as application/json.

Here is a small example:

interface Payload {
  id: string;
  data: number;
}

...

const submit = useSubmit();

...

const payload: Payload = { ... };

submit(payload, { method: "POST", encType: "application/json" });

submit is typed in a way where it requires object types to have index signatures. This makes it impossible to use interfaces unless they themselves declare an index signature, because they don't have any implicitly.

Type aliases or types inferred from anonymous objects do have implicit index signatures so they work.

In simple cases I can work around this by spreading payload into an empty object:

submit({ ...payload }, { method: "POST", encType: "application/json" });

This works because the resulting type is now { id: string, data: number } which implicitly has an index signature. It stops working however if there are any properties that are typed by an interface.

Is this by design? Am I doing something wrong?

[szszoke]

Another workaround that I found is a utility type that converts creates an anonymous type based on an interface:

type Primitives = string | number | boolean;

type AnonymizeProperty<T> = T extends Primitives
  ? T
  : Anonymize<T>;

type Anonymize<T> = { [K in keyof T]: AnonymizeProperty<T[K]> };

It seems to work in my case but I haven't tested it with arrays.