`type` field cause exception

[b3g00d]

Used Cerberus version / latest commit: 1.3.2

• I have the capacity to improve the docs when my problem is solved.

• I have the capacity to submit a patch when a bug is identified.

• [ x] My question does not concern a practical use-case that I can't figure out
  to solve.

---

Bug report / Feature request

I have a sample schema:

{'metadata': {'type': 'dict',
  'nullable': True,
  'schema': {'image_thumb': {'type': 'list',
    'required': False,
    'default': [],
    'minlength': 0,
    'maxlength': 10,
    'schema': {'type': 'dict',
     'default': None,
     'nullable': True,
     'schema': {'width': {'type': 'integer', 'required': True}}}}}}}

Expected: return image_thumb must be a list

it will return an exception when an object was {'metadata': {'image_thumb': {'type': 'error'}}}
with type in the body.

[funkyfuture]

please provide a unit test that is as sparse as possible to replicate the problem? it would also be helpful if you provided the full traceback of the exception.

[b3g00d]

Example use-case:

import cerberus

schema = {
    "metadata": {
        "type": "dict",
        "nullable": True,
        "schema": {
            "image_thumb": {
                "type": "list",
                "required": False,
                "default": [],
                "minlength": 0,
                "maxlength": 10,
                "schema": {
                    "type": "dict",
                    "default": None,
                    "nullable": True,
                    "schema": {
                        "width": {"type": "integer", "required": True},
                    },
                },
            },
        },
    }
}

objType2Name = {"metadata": {"image_thumb": {"type2": "error"}}}
objTypeName = {"metadata": {"image_thumb": {"type": "error"}}}
val = cerberus.Validator(schema)

# This will return False as expected
val.validate(objType2Name)
# [Out]# False
#
# This wwill raise Error
val.validate(objTypeName)

Output

Traceback (most recent call last):
  File "sample.py", line 32, in <module>
    val.validate(objTypeName)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 990, in validate
    self.__normalize_mapping(self.document, self.schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 671, in __normalize_mapping
    self.__normalize_containers(mapping, schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 748, in __normalize_containers
    self.__normalize_mapping_per_schema(field, mapping, schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 812, in __normalize_mapping_per_schema
    result_value = validator.normalized(mapping[field], always_return_document=True)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 646, in normalized
    self.__normalize_mapping(self.document, self.schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 671, in __normalize_mapping
    self.__normalize_containers(mapping, schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 748, in __normalize_containers
    self.__normalize_mapping_per_schema(field, mapping, schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 812, in __normalize_mapping_per_schema
    result_value = validator.normalized(mapping[field], always_return_document=True)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 646, in normalized
    self.__normalize_mapping(self.document, self.schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 660, in __normalize_mapping
    self.__normalize_rename_fields(mapping, schema)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 864, in __normalize_rename_fields
    self._normalize_rename(mapping, schema, field)
  File "/home/begood/.local/share/virtualenvs/api-u0lUFnib/lib/python3.7/site-packages/cerberus/validator.py", line 877, in _normalize_rename
    if 'rename' in schema[field]:
TypeError: argument of type 'NoneType' is not iterable

[funkyfuture]

that's an interesting edge case:

@mark.parametrize(
    ("outer_type", "inner_type"), product(("dict", "list"), ("dict", "list"))
)
def test_normalization_of_dict_with_a_field_named_type(
    outer_type, inner_type
):
    # https://github.com/pyeve/cerberus/issues/545

    validator = Validator(
        {"document": {"type": outer_type, "schema": {"type": inner_type,},},}
    )
    # this test seems to only fail when the token "type" is used as key:
    validator({"document": {"type": None}})    

---

regardless, you're aware that the image_thumb field would expect a list, are you?

[b3g00d]

@funkyfuture Yes, I know that but someone will input object with wrong type. And I need Cerberus to return an error instead of an exception.

[funkyfuture]

i haven't gone my step debugging routes through this, but it's quiet certain that it stems from the ambiguity of the schema rule with regards to lists and dicts. if so, i doubt that this is fixable. the next major release would have thrown the ambiguity over board. hence i'm considering this as a no-fix from my side.

if you don't want to try to fix it yourself, consider to first rename the field type and later re-rename it. or just test against a schema where the field is first renamed if you aren't using a normalized result anyway.