Using types-jsonschema 4.4.0, mypy does not consider `jsonschema.validators.Draft7Validator` a type

[DMRobertson]

(I'm not sure if this is best filed as an issue against typeshed or mypy. Happy to move this if it's the latter.)

The snippet

import jsonschema
x: jsonschema.Draft7Validator

does not typecheck on with types-jsonschema 4.4.0.

error: Variable "jsonschema.validators.Draft7Validator" is not valid as a type  [valid-type]

For cross referencing, we noticed this here.

The snippet above does type-check with 4.3.0, where Draft7Validator was annotated as Any. The change was made in #7025 .

Are we misunderstanding or misusing Draft7Validator - is it not expected to be a type like this? If not, perhaps this is a problem in mypy rather than the stubs?

For what it's worth: mypy's documentation suggests that tp: Type[_Validator] is considered a "variable of type _Validator". Perhaps mypy's complaint is that tp's value could be a replaced with a different subtype of _Validator at runtime? With that in mind, I tried patching the stubs to read Draft7Validator: Final[type[_Validator]] but this didn't seem to appease the type gods.

[DMRobertson]

Come to think of it, maybe Draft7Validator = NewType("Draft7Validator", _Validator) would do the trick?

[Akuli]

We should probably just use empty classes with _Validator as a base class, as in class Draft7Validator(_Validator): .... At runtime, jsonschema has a function that creates a new validator class, and making new classes in typeshed is the closest we can get to that.