fix: 🐛 accurate auth typings

[damusix]

Previously would resolve to any, they now pickup the generic and the ref overrides.

[Marsup]

You're not picking the keys of U, I think we're going to miss some parts unless we do this

Suggested change

	export type MergeType<T, U> = {
	[K in keyof T]: K extends keyof U
	? U[K]
	: T[K];
	};
	export type MergeType<T, U> = {
	[K in keyof T]: K extends keyof U
	? U[K]
	: T[K];
	} & U;

[damusix]

U would be what you're extending from. Hapi only uses T, which is ReqRefDefaults in the latter utility type, so any extra properties you might add in the reference type U are unused if they're not the same as T. This makes intersecting unnecessary.

Does it give you any issues?

[Marsup]

Nope, but MergeType as a generic type can be abused with a mismatch of keys. If it's not doing an actual merge of keys, maybe it should be named otherwise.

[damusix]

Agreed. What name do you suggest? It should only care about objects related to hapi internal types. Anything else would be unused. It merges from left to right, so perhaps ApplyLeft ?

[Marsup]

I'm wondering, what difference does it make to remove all those extends?

[damusix]

Technically you can say that User is a string and hapi will accept it

[Marsup]

It looks like the types were trying to be prescriptive in "good" practices, should we just stick with what hapi does then?

[damusix]

The reason I removed it was because, to me, it's like the decorator types where it expects you to pass a function but in reality you can pass anything and it will decorate. I think we should type reality, no? IFAIK, technically, credentials and artifacts can be a single primitive value; so can app, so can user. Hapi does not internally use any of these values. These are user-defined and I think the user should dictate how they need to build their auth.

Example:

https://github.com/hapijs/basic/blob/master/lib/index.js#L64
https://github.com/hapijs/jwt/blob/master/lib/plugin.js#L225

They're never used and can be anything at runtime.

However, if you think we should communicate that these must be objects, I won't disagree either because it's not wrong. I've never not-used an object in these abstractions.