Cannot dereference top level '$ref'

[fgiuba]

I'm trying to use jsonref to expand a JSON Schema which has a top level $ref but I'm getting a ValueError.

This is enough to to reproduce the issue:

schema = '{"definition": "helloworld", "$ref": "#/definition"}'
print(jsonref.loads(schema))

And this is the error:

Traceback (most recent call last):
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 252, in __subject__
    return self.cache
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 176, in __getattribute__
    return _oga(self, attr)
AttributeError: 'JsonRef' object has no attribute 'cache'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/jsonref.py", line 178, in callback
    base_doc = self.loader(uri)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/jsonref.py", line 299, in __call__
    result = self.get_remote_json(uri, **kwargs)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/jsonref.py", line 316, in get_remote_json
    result = json.loads(urlopen(uri).read().decode("utf-8"), **kwargs)
  File "/usr/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 509, in open
    req = Request(fullurl, data)
  File "/usr/lib/python3.8/urllib/request.py", line 328, in __init__
    self.full_url = url
  File "/usr/lib/python3.8/urllib/request.py", line 354, in full_url
    self._parse()
  File "/usr/lib/python3.8/urllib/request.py", line 383, in _parse
    raise ValueError("unknown url type: %r" % self.full_url)
ValueError: unknown url type: ''

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/shishax/.config/JetBrains/PyCharm2022.1/scratches/jsonref-test.py", line 5, in <module>
    print(jsonref.loads(schema))
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 202, in proxied
    args.insert(arg_pos, self.__subject__)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 176, in __getattribute__
    return _oga(self, attr)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 134, in wrapper
    return method(self, *args, **kwargs)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 254, in __subject__
    self.cache = super(LazyProxy, self).__subject__
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 134, in wrapper
    return method(self, *args, **kwargs)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 240, in __subject__
    return self.callback()
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 134, in wrapper
    return method(self, *args, **kwargs)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/jsonref.py", line 180, in callback
    self._error("%s: %s" % (e.__class__.__name__, unicode(e)), cause=e)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/proxytypes.py", line 134, in wrapper
    return method(self, *args, **kwargs)
  File "/home/shishax/.env/sam-test-jsonref/lib/python3.8/site-packages/jsonref.py", line 223, in _error
    raise JsonRefError(
jsonref.JsonRefError: ValueError: unknown url type: ''

Is it allowed to have a top level $ref?
I didn't found any mention in the docs.

[gazpachoking]

The spec says that other keys within the reference object shall be ignored. Your reference object contains the definitions key that the reference is trying to point to, so no, I don't think this is supported. That being said, I'll try to take a peek to see if the error can be made any better.

[gazpachoking]

Yeah, at best this is a reference that refers to itself. I didn't figure out an easy way to improve the error message, but this is not supported by the jsonref spec.