JSONDecodeError / RefResolutionError validating the issued field of a CSL item

[dhimmel]

Greetings, I'm new to using this library and would like to validate objects based on the Citation Styles Language schema as part of https://github.com/greenelab/manubot/issues/47.

In the code snippet below with Python v3.6.6 and jsonschema v2.6.0, I'm getting a JSONDecodeError / RefResolutionError. If I remove the issued object of my CSL data, there are no errors. issued is defined in the schema as:

            "issued": {
                "$ref": "date-variable" 
            },

I saw in https://github.com/Julian/jsonschema/issues/343 and https://github.com/Julian/jsonschema/pull/371 that there may be some complexities with internal reference resolution. Not sure if that is the issue here.

Code snippet

import json
import jsonschema
import requests

# Load instance
csl = r'''\
[
  {
    "issued": {
      "date-parts": [
        [
          "2014",
          "07",
          "14"
        ]
      ]
    },
    "type": "report",
    "id": "nkzHjOdS"
  }
]
'''
csl = json.loads(csl)

# Load schema
url = 'https://github.com/citation-style-language/schema/raw/4846e02f0a775a8272819204379a4f8d7f45c16c/csl-data.json'
schema = requests.get(url).json()
jsonschema.Draft3Validator.check_schema(schema)
validator = jsonschema.Draft3Validator(schema)

# Validate
errors = list(validator.iter_errors(csl))

Stacktrace / error

```python-traceback --------------------------------------------------------------------------- JSONDecodeError Traceback (most recent call last) ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in resolve_from_url(self, url) 382 try: --> 383 document = self.resolve_remote(url) 384 except Exception as exc: ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in resolve_remote(self, uri) 468 if callable(requests.Response.json): --> 469 result = requests.get(uri).json() 470 else: ~/anaconda3/lib/python3.6/site-packages/requests/models.py in json(self, **kwargs) 895 pass --> 896 return complexjson.loads(self.text, **kwargs) 897 ~/anaconda3/lib/python3.6/json/__init__.py in loads(s, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw) 353 parse_constant is None and object_pairs_hook is None and not kw): --> 354 return _default_decoder.decode(s) 355 if cls is None: ~/anaconda3/lib/python3.6/json/decoder.py in decode(self, s, _w) 338 """ --> 339 obj, end = self.raw_decode(s, idx=_w(s, 0).end()) 340 end = _w(s, end).end() ~/anaconda3/lib/python3.6/json/decoder.py in raw_decode(self, s, idx) 356 except StopIteration as err: --> 357 raise JSONDecodeError("Expecting value", s, err.value) from None 358 return obj, end JSONDecodeError: Expecting value: line 1 column 1 (char 0) During handling of the above exception, another exception occurred: RefResolutionError Traceback (most recent call last) in () 29 30 # Validate ---> 31 errors = list(validator.iter_errors(csl)) ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in iter_errors(self, instance, _schema) 103 104 errors = validator(self, v, instance, _schema) or () --> 105 for error in errors: 106 # set details if not already set by the called fn 107 error._set( ~/anaconda3/lib/python3.6/site-packages/jsonschema/_validators.py in items(validator, items, instance, schema) 53 if validator.is_type(items, "object"): 54 for index, item in enumerate(instance): ---> 55 for error in validator.descend(item, items, path=index): 56 yield error 57 else: ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in descend(self, instance, schema, path, schema_path) 119 120 def descend(self, instance, schema, path=None, schema_path=None): --> 121 for error in self.iter_errors(instance, schema): 122 if path is not None: 123 error.path.appendleft(path) ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in iter_errors(self, instance, _schema) 103 104 errors = validator(self, v, instance, _schema) or () --> 105 for error in errors: 106 # set details if not already set by the called fn 107 error._set( ~/anaconda3/lib/python3.6/site-packages/jsonschema/_validators.py in properties_draft3(validator, properties, instance, schema) 251 subschema, 252 path=property, --> 253 schema_path=property, 254 ): 255 yield error ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in descend(self, instance, schema, path, schema_path) 119 120 def descend(self, instance, schema, path=None, schema_path=None): --> 121 for error in self.iter_errors(instance, schema): 122 if path is not None: 123 error.path.appendleft(path) ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in iter_errors(self, instance, _schema) 103 104 errors = validator(self, v, instance, _schema) or () --> 105 for error in errors: 106 # set details if not already set by the called fn 107 error._set( ~/anaconda3/lib/python3.6/site-packages/jsonschema/_validators.py in ref(validator, ref, instance, schema) 210 yield error 211 else: --> 212 scope, resolved = validator.resolver.resolve(ref) 213 validator.resolver.push_scope(scope) 214 ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in resolve(self, ref) 373 def resolve(self, ref): 374 url = self._urljoin_cache(self.resolution_scope, ref) --> 375 return url, self._remote_cache(url) 376 377 def resolve_from_url(self, url): ~/anaconda3/lib/python3.6/site-packages/jsonschema/validators.py in resolve_from_url(self, url) 383 document = self.resolve_remote(url) 384 except Exception as exc: --> 385 raise RefResolutionError(exc) 386 387 return self.resolve_fragment(document, fragment) RefResolutionError: Expecting value: line 1 column 1 (char 0) ```

[dhimmel]

One workaround is dereference the schema before feeding it to jsonschema. I was able to do this with the jsonref package

import jsonref
schema = jsonref.load_uri(url, jsonschema=True)

[Julian]

This is almost certainly one of the other two issues there.

Closing this one, since it's tied up in all the other unrelated stuff, but feel free to follow those.