Validate formats in check_schema

[alliefitter]

I'm wondering if there's a way to validate formats when using check_schema. It seems to allow invalid format names. The below example passes validation, even though datetime should be date-time. I noticed the concrete implementation of check_schema has a format_checker argument (even though the FormatChecker protocol does not have this argument). Setting the format checker doesn't validate format names either. Is there anyway to get check_schema to fail for invalid formats?

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "foo": {"type": "string", "minLength": 2},
    "bar": {"type": "number", "minimum": 10},
    "baz": {"type": "string", "format": "datetime"}
  }
}

[Julian]

Hey there.

Those actually aren't invalid formats according to the spec unfortunately.

Specifically, implementations are supposed to ignore formats that aren't known to them. (See e.g. https://json-schema.org/draft/2020-12/json-schema-validation#name-implementation-requirements)

The general answer to this I still consult is "a schema is not a replacement for your tests", so you should notice this by having a test you can't fail. But if you persist, you can also write a metaschema which constrains the set of formats to just the ones known by the library and then use that to validate your schema as well.