chore(gatsby): migrate derived-types to TypeScript

[sasurau4]

Description

Part of #21995

I migrated derived-types.js to TS.

Documentation

Related Issues

#21995

[LekoArts]

Sorry for the late response on this. Can you please rebase onto master? Thanks!

[pvdz]

I'm looking into the return type here.

I can see in https://graphql-compose.github.io/docs/api/ObjectTypeComposer.html that the returned type is Extensions. Unfortunately that does not describe the type. The default being a Set is a hint, but a Set of what ...

https://github.com/graphql-compose/graphql-compose/blob/master/src/utils/definitions.d.ts#L16 implies that it is:

export type Extensions = {
  [key: string]: any;
  directives?: ExtensionsDirective[];
};

But that doesn't seem right since we default to a Set, AND we call .add on it in addDerivedType() (see later in this file).

  const derivedTypes = getDerivedTypes({ typeComposer })
  typeComposer.setExtension(`derivedTypes`, derivedTypes.add(derivedTypeName))

So this feels a little troubling, to say the least.

@vladar do you perhaps have an insight here? Do we have a bug in our code or am I looking at the wrong docs?

[vladar]

I can see in https://graphql-compose.github.io/docs/api/ObjectTypeComposer.html that the returned type is Extensions

It is the returned type of getExtensions method. But we are looking at getExtension which has any as the returned type. Extension can be basically anything we want. In our case derivedTypes extension is a Set | void.

[sasurau4]

Thanks for sharing your insight. I tried to fix it.

[pvdz]

Great! Thank you 💜