Python jsonschema tries to resolve $ref as a remote url. Why is it doing this?

Question

When I attempt to validate some data with a schema:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "splash::schema::user",
  "type": "object",
  "title": "User Schema",
  "definitions": {
    "authenticator": {
      "type": "object",
      "required": [
        "issuer",
        "subject"
      ],
      "properties": {
        "issuer": {
          "type": "string",
          "description": "name of the issuer"
        },
        "subject": {
          "type": "string",
          "description": "unique subject id"
        }
      }
    }
  },
  "authenticators": {
    "type": "array",
    "items": {
      "$ref": "#/definitions/authenticator"
    }
  },
  "required": [
    "uid",
    "name"
  ]
}

I am getting this error from the python jsonschema library:

 File "site-packages/jsonschema/validators.py", line 774, in resolve_from_url
    document = self.store[url]
  File "site-packages/jsonschema/_utils.py", line 22, in __getitem__
    return self.store[self.normalize(uri)]
KeyError: ''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "site-packages/jsonschema/validators.py", line 777, in resolve_from_url
    document = self.resolve_remote(url)
  File "site-packages/jsonschema/validators.py", line 863, in resolve_remote
    with urlopen(uri) as url:
  File "/usr/lib/python3.6/urllib/request.py", line 223, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.6/urllib/request.py", line 511, in open
    req = Request(fullurl, data)
  File "/usr/lib/python3.6/urllib/request.py", line 329, in __init__
    self.full_url = url
  File "/usr/lib/python3.6/urllib/request.py", line 355, in full_url
    self._parse()
  File "/usr/lib/python3.6/urllib/request.py", line 384, in _parse
    raise ValueError("unknown url type: %r" % self.full_url)
ValueError: unknown url type: ''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "site-packages/flask_restful/__init__.py", line 468, in wrapper
    resp = resource(*args, **kwargs)
  File "site-packages/flask/views.py", line 89, in view
    return self.dispatch_request(*args, **kwargs)
  File "site-packages/flask_restful/__init__.py", line 583, in dispatch_request
    resp = meth(*args, **kwargs)
  File "splash-server/splash/resource/base.py", line 40, in post
    issues = self.service.validate(data)
  File "splash-server/splash/service/base.py", line 25, in validate
    for error in errors:
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 328, in iter_errors
    for error in errors:
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/_validators.py", line 286, in properties
    schema_path=property,
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 344, in descend
    for error in self.iter_errors(instance, schema):
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 328, in iter_errors
    for error in errors:
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/_validators.py", line 81, in items
    for error in validator.descend(item, items, path=index):
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 344, in descend
    for error in self.iter_errors(instance, schema):
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 328, in iter_errors
    for error in errors:
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/_validators.py", line 259, in ref
    scope, resolved = validator.resolver.resolve(ref)
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 766, in resolve
    return url, self._remote_cache(url)
  File "splash-server/env/lib/python3.6/site-packages/jsonschema/validators.py", line 779, in resolve_from_url
    raise exceptions.RefResolutionError(exc)
jsonschema.exceptions.RefResolutionError: unknown url type: ''

The jsonschema library shouldn't be trying to make a request to a url. I don't understand why it isn't just referencing the definitions field in the file. When I replaced the "items": {"$ref": "#/definitions/authenticator"} with the corresponding definition it worked fine. So I assume that jsonschema is erroneously trying to request a remote url.

Some braces don't match in that schema definition. was there a mispaste? — Ether, Jul 20 '20 at 20:37
It was only a copy paste error though. It was not the underlying problem. — Joshua Avery, Jul 20 '20 at 22:37
Did you fix the issue? If not could you provide a code sample. I found this post useful for what I was doing: https://stackoverflow.com/questions/53968770/how-to-set-up-local-file-references-in-python-jsonschema-document — Tim Ludwinski, Nov 18 '20 at 21:23
We can't help you if you don't paste in the python script you used. — falsePockets, Feb 13 '23 at 00:57

Python jsonschema tries to resolve $ref as a remote url. Why is it doing this?

0 Answers0