Expose IValidator via PEP544 Protocols

I have an issue similar to #239 but somewhat different. I would like to be able to reach IValidator to use type-hinting in functions.

If I want to create a function where a validator can be passed in parameter, it cannot be type-hinted:

def handle_ndjson(
  path:str, 
  validator:jsonschema.IValidator, 
  valid_object_fn: Callable[[dict], None], 
  invalid_object_fn: Callable[[dict, jsonschema.ValidationException], None]):

fails because jsonschema.IValidator isn’t exposed (as explained in #239). The purpose is not to allow the creation of new validator, but to allow the user to chose between the different draft. Is there a graceful way to do that?

[sirosen]

With this now in 4.3.0 (huge thanks @Julian for the steady review feedback and quick release!), I think we can close this issue.

I have a PR open in typeshed to add this, after which it should be possible to use jsonschema.Validator for type annotations.

For those who did not see the PR, I’ll also note here that jsonschema.Validator is runtime_checkable, meaning you can use it for isinstance checks.

[sirosen]

Yes, having jsonschema publish types would also be a solution. Arguably the best solution for library consumers. But, not to downplay the value it offers, I don’t think it’s likely to happen in the near term.

jsonschema dynamically generates classes, and type checkers struggle to support dynamic cases like this. I see problems with trying to have jsonschema publish types based on its runtime logic. And I would argue that stubs will end up better maintained in typeshed than here.