Fix input type on some methods and add `AssertingValidator`

[cpiber]

Fixes #222

• Some functions incorrectly used value: T instead of value: unknown (want to assert value is T, not assume it)
• Added type to make ReusableValidator also assert value is T
• Convenience type to infer nested BasePredicate for object.partialShape (type-check that type and predicate are equal)

I am not fully sure about the last two points, suggestions welcome.

[cpiber]

@sindresorhus Input?

[cpiber]

While this isn't resolved, you can use

const is = <T>(v: unknown, pred: BasePredicate<T>): v is T => ow.isValid(v, pred);

to substitute ow.isValid

[cpiber]

For some reason, I cannot reply to the review, so here:

Shouldn't the asserts be added to ReusableValidator?

I tried that, but then you get Assertions require every name in the call target to be declared with an explicit type annotation.ts(2775) as mentioned before

Why not improve the exactShape type instead of adding a separate type here?

First of all, I didn't want to cause breaking changes, and second, I don't know if it is possible to do that, and if it is how. As I said, I introduced that type to make sure TypeScript actually verifies, that the shape of the argument and the type of what I want to verify against are the same, since simply declaring the target variable as ObjectValidator<> does not work. Please do suggest a better solution.

[sindresorhus]

I tried that, but then you get Assertions require every name in the call target to be declared with an explicit type annotation.ts(2775) as mentioned before

I would try to investigate that. Maybe there's a workaround. I don't have time to look into these issues now.

First of all, I didn't want to cause breaking changes, and second, I don't know if it is possible to do that, and if it is how. As I said, I introduced that type to make sure TypeScript actually verifies, that the shape of the argument and the type of what I want to verify against are the same, since simply declaring the target variable as ObjectValidator<> does not work. Please do suggest a better solution.

I unfortunately don't have time to look for a better solution.

I suggest removing the unrelated changes for now and focus on "Some functions incorrectly used value: T instead of value: unknown (want to assert value is T, not assume it)". The other things can be done later on in a separate pull request or opened as an issue instead if you cannot find a good solution for it.

[cpiber]

I would try to investigate that. Maybe there's a workaround. I don't have time to look into these issues now.

I don't think it's possible due to the nature of ow.create: TS(2775) requires the variable to which ow.create's return is saved to to be explicitly typed from what I understand, I already tried to search for a better solution.

I suggest removing the unrelated changes for now

Understood, I'll remove them in a sec

[sindresorhus]

AssertingValidator should not be exported to the user. It's only meant for the tests here.

[cpiber]

Is it? In my opinion, it should be exported, so that the user can have a validator, that actually asserts

[sindresorhus]

The intention for that was not clear. Then it needs a proper doc comment with a description (including why it exists) and a usage example.