Support for any iterable (instead of just list) in "allowed" rule.

[crunk1]

Used Cerberus version / latest commit: 1.2
Python version: 3.6.5

• I consulted these documentations:

  • http://docs.python-cerberus.org/en/stable/
  • http://docs.python-cerberus.org/en/latest/

• I found nothing relevant to my problem in the docs.

• I found the documentation not helpful to my problem.

• 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.

---

Use-case abstract

I suggest adding support for using iterables in the "allowed" validation rule. In particular, I have a string enum class derived from enum.Enum. An enum.Enum is iterable. I'll try to demonstrate my use case:

class MyEnum(StrEnum):
  FOO = 'FOO'

# Behavior of MyEnum
# list(MyEnum)         -> [<MyEnum.FOO: 'FOO'>]
# 'FOO' in MyEnum      -> True
# 'BAR' in MyEnum      -> False
# MyEnum.FOO in MyEnum -> True
# MyEnum.FOO == 'FOO'  -> True
# MyEnum.FOO == 'BAR'  -> False

# This works, but is undesirable:
schema = {
  'foo': {'type': 'list', 'allowed': list(MyEnum)},
}
v = cerberus.Validator(schema)
# v.validate({'foo': [MyEnum.FOO, 'FOO']}) -> True

# This raises an error:
schema = {
  'foo': {'type': 'list', 'allowed': MyEnum},
}
v = cerberus.Validator(schema)
# Traceback (most recent call last):
#   File "<input>", line 1, in <module>
#   File "C:\Python36\lib\site-packages\cerberus\validator.py", line 169, in __init__
#     self.schema = kwargs.get('schema', None)
#   File "C:\Python36\lib\site-packages\cerberus\validator.py", line 509, in schema
#     self._schema = DefinitionSchema(self, schema)
#   File "C:\Python36\lib\site-packages\cerberus\schema.py", line 69, in __init__
#     self.validate(schema)
#   File "C:\Python36\lib\site-packages\cerberus\schema.py", line 197, in validate
#     self._validate(schema)
#   File "C:\Python36\lib\site-packages\cerberus\schema.py", line 219, in _validate
#     raise SchemaError(self.schema_validator.errors)
# cerberus.schema.SchemaError: {'foo': [{'allowed': ['must be of list type']}]}

[funkyfuture]

afaict, supporting this would just require to change the rule's constraint schema to type.collections.Container. therefore the schema validator would need a type definition for that. that shouldn't be too tricky once you wrapped your head around the schema validation mechanics.

[crunk1]

Mind filling me in on the mechanics? I've been looking for usages of _validate_allowed and can't see where it is used. Is there some autogen tooling built around the rule schemas?

[crunk1]

Nvm, think I found it :)

[crunk1]

PR out. #388