Make $schema lookup more liberal for empty fragment URLs

[jswinarton]

I have a valid schema document that contains the following $schema value:

{
  "$schema": "http://json-schema.org/draft-07/schema/#"
}

When validating an instance against this schema, I get the following warning:

/usr/local/lib/python3.7/site-packages/jsonschema/validators.py:893: DeprecationWarning: The metaschema specified by $schema was not found. Using the latest draft to validate, but this will raise an error in the future.

I discovered that I can suppress the error by changing removing the trailing slash and hash from the schema URI, e.g. http://json-schema.org/draft-07/schema.

I think the validator should allow for some variations on URI formats--the JSON Schema documentation specifies the $schema value with the trailing slash and hash, so I believe that will be the most common format users attempt.

[Julian]

This looks reasonable -- I'm not sure we want to accept multiple variations on its own, but really it depends what the JSON Schema spec says (if anything) about whether those URLs are the same or not as far as its concerned. Probably you're right that they are.

So yeah definitely thanks for filing.

[wmarcuse]

I get the same DepriciationWarning when I create a reusable schema validator:

validator_class = jsonschema.validators.validator_for(SCHEMA)
validator = validator_class(schema=SCHEMA, format_checker=jsonschema.FormatChecker())

Specifying the draft version validator did the trick:

validator_class = jsonschema.validators.Draft7Validator
validator = validator_class(schema=SCHEMA, format_checker=jsonschema.FormatChecker())

[lcvisser]

Maybe also accept both http:// and https://?

[anriijmind]

@wmarcuse Could you give, please, an example with validating schema and response? Because I don't understand what should I do with validator = validator_class(schema=SCHEMA, format_checker=jsonschema.FormatChecker()), if warning shows in that code
validate(instance=respose_json, schema=schema)
Schema has this type "$schema": "http://json-schema.org/schema#"

and I have this error:
/lib/python3.8/site-packages/jsonschema/validators.py:928: DeprecationWarning: The metaschema specified by $schema was not found. Using the latest draft to validate, but this will raise an error in the future. cls = validator_for(schema)

[Hoohm]

I have the same error as you @anriijmind
Using this link : http://json-schema.org/draft/2020-12/schema

[anriijmind]

I have the same error as you @anriijmind
Using this link : http://json-schema.org/draft/2020-12/schema

Still warning shows.
Tried:

1. "$schema": "http://json-schema.org/schema#" -> "$schema": "http://json-schema.org/draft/2020-12/schema#"
2. "$schema": "http://json-schema.org/schema#" -> "$schema": "http://json-schema.org/draft/2020-12/schema"

I have jsonschema "version": "==3.2.0"

[Kaelink]

I had the same issue, but the README only claims support for:

Full support for Draft 7, Draft 6, Draft 4 and Draft 3

Changing to http://json-schema.org/draft-07/schema# therefore solved the warning in my case.

[anriijmind]

I had the same issue, but the README only claims support for:

Full support for Draft 7, Draft 6, Draft 4 and Draft 3

Changing to http://json-schema.org/draft-07/schema# therefore solved the warning in my case.

Thanks, it solves warning

[Julian]

Given the combination of some of what's proposed here being against the spec, and the rest being fairly easy to do by simply ensuring you use precisely the identifier that the meta schema says you should, I'm going to WONTFIX this.

You can see some additional discussion at the bottom of #822.

If you really insist on (or have a use case where) you cannot change what's in the actual schema itself, something like your_schema["$schema"] = Draft4Validator.META_SCHEMA["$id"] just before you call validate works as well.