[typescript] How to type the context?

In the authentication example it’s possible to extend the context, but this is not typed when noImplicitThis is set to true. 'this' implicitly has type 'any' because it does not have a type annotation “noImplicitThis”.

It would be nice if this was automatically being done by using the type of the getContext function.

“Solutions”:

• noImplicitThis setting this to false
• // @ts-ignore ignore the error
• Typing the this parameter. See https://www.typescriptlang.org/docs/handbook/functions.html#this-parameters This solution won’t work well, because now the frontend also expects an extra parameter.

[michie1]

I was re-reading the issue and saw one of my first “solutions”.

* Typing the `this` parameter. See https://www.typescriptlang.org/docs/handbook/functions.html#this-parameters This solution won't work well, because now the frontend also expects an extra parameter.

This solution in combination with FooMinusContext applied to each function would work as well I think. I’ll try to make that type. If it works correctly the only thing the library needs to do is exporting that type. It won’t be a breaking change.

[michie1]

Just some brainstorming, I’m thinking how to omit using this:

A: Could it be possible to export a function getContext() from the library which can be used in the function declaration? On the server we might need to call const wc = wildcard.init<Context>(); When the function is called on the client side it’s connected to request (e.g. Express) middle ware.

B: On the frontend you call a function for example with foo(5), but on the backend you can define the function as foo(context: Context, value: number). On the frontend you could use a wrapper type that omits the first parameter.

type Context = {
  foo: number;
};

function foo(context: Context, a: number) {
  return a + context.foo;
}

type FooType = typeof foo;
type FooMinusContext = FooType extends (context: Context, ...rest: infer U) => infer R
  ? (...rest: U) => R
  : never;

https://github.com/reframejs/wildcard-api/blob/3ed87113503cb75d09a7cb4f5669a7ba9fe26371/server/WildcardServer.ts#L287

Here you could inject the context as first argument. Potentially you could place it as last argument and keep using the thisArgument of the apply function, so Javascript users can keep using it the current way, while Typescript users could use the correctly typed version.