error path is missing when using iter_errors

[wichert]

I have a very basic schema:

    schema = {
           '$schema': 'http://json-schema.org/draft-04/schema',
           'type': 'object',
           'properties': {
               'email': {
                   'type': 'string',
                   'format': 'email',
               },
               'password': {
                    'type': 'string',
                    'minLength': 1,
               },
           },
           'additionalProperties': False,
           'required': ['email', 'password'],
    }

When I validate an empty map against that I can see two errors:

>>> validator = validator_for(schema)
>>> errors = list(validator(schema).iter_errors(data))
>>> errors
[<ValidationError: "'email' is a required property">,
 <ValidationError: "'password' is a required property">]

Creating an error tree fails shows some odd behaviour:

>>> et = jsonschema.ErrorTree(validator(schema).iter_errors(data))
>>> et
<ErrorTree (1 total errors)>
>>>  'email' in et
False

Trying to figure out why this happened revealed that the error path is empty:

>>> [e.path for e in errors]
[deque([]), deque([])]

[Julian]

This is expected, though maybe underdocumented.

path means "where in the instance the error occured", and should always be a sequence of indexes that can be performed against the instance.

required is validated at the level of the object that should contain the properties (here your root object), so the path is empty.

Try your example with any other validator, or any nested object.

[wichert]

Hm, that is problematic for me. My use case here is doing validation on data past to a REST service, and I would like to report all errors back to the client, which I can't do now due to the missing path. As far as I can see there is no other way to see which property triggered the error. This is the __dict__ if the error:

{'cause': None,
 'context': [],
 'instance': {},
 'message': "'email' is a required property",
 'parent': None,
 'path': deque([]),
 'relative_path': deque([]),
 'relative_schema_path': deque(['required']),
 'schema': {'additionalProperties': False,
            'properties': {'email': {'format': 'email', 'type': 'string'},
                           'password': {'minLength': 1, 'type': 'string'}},
            'required': ['email', 'password'],
            'type': 'object'},
 'schema_path': deque(['required']),
 'validator': 'required',
 'validator_value': ['email', 'password']}

Can you consider adding some way to see which property triggered the error?

[Julian]

You're already seeing every error.

If you mean you want to know specifically for required which properties are missing, that's #119, patches certainly welcome.

[wichert]

I'll see if I can take a stab at that. One thing that has me a little confused is that the behaviour is not consistent: when using jsonschema.validate() instead of lazy validation the error exception does have the missing property in path. Reading the discussion in #119 I am wondering if that is a bug, since you mention the path should always be reachable, or if there is a specific reading for the different in behaviour?

[handrews]

@wichert you might be interested in the discussion in json-schema-org/json-schema-spec#396, about standardizing or at least recommending output/error formats. Note that that's on the spec repo, not this implementation. It's also just getting off the ground despite having been filed a while back.

[Julian]

when using jsonschema.validate() instead of lazy validation the error exception does have the missing property in path

What code are you running and what path are you looking at?

The behavior here should match between iter_errors and validate (and the latter actually just uses the former).

[Julian]

Going to close this given the above (but if you do have a case where this has different behavior definitely lemme know!) and given @handrews's pointer, which I'll have to have a look at myself.