Negative filter on "format"

[Stranger6667]

I noticed that jsonschema doesn't raise errors when the input string does not match the "format" (as per docs)

This behavior leads to unsatisfiable errors when the "not" keyword is involved. For example:

from hypothesis_jsonschema import from_schema

from_schema({'type': 'string', 'not': {'format': 'date'}}).example()

...

Unsatisfiable: Unable to satisfy assumptions of hypothesis example_generating_inner_function.

However, as hypothesis-jsonschema generates values matching certain formats, then it seems to me that it should also be able to generate values NOT matching them.

I assume that it could be solved by passing the right format_checker to jsonschema validators.

What do you think?

[Zac-HD]

I think the current behaviour is strictly correct, since the spec is careful to treat format as advisory. However, I think your idea of adding a format checker should do the trick without requiring any change to hypothesis-jsonschema: see

https://github.com/Zac-HD/hypothesis-jsonschema/blob/1c5f107230ccbd48c66d7c6693833745a598e294/src/hypothesis_jsonschema/_from_schema.py#L158-L166

[Stranger6667]

Thanks! I think the issue could be closed, then :)