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pythonpython-3.10marshmallow-dataclass

marshmallow NewType can not be turned into a dataclass, python 3.10

I'm in the process of upgrading to python 3.10 and in that context I thought it would be nice to also upgrade packages used. Right now, the problem is with the marshmallow packages and at this point I can't even run their example code for NewType anymore.

This is my code (taken from the comment in the NewType definition):

from marshmallow_dataclass import NewType, dataclass, List
import marshmallow.validate
IPv4 = NewType('IPv4', str, validate=marshmallow.validate.Regexp(r'^([0-9]{1,3}\\.){3}[0-9]{1,3}$'))

@dataclass
class MyIps:
   ips: List[IPv4]

MyIps.Schema().load({"ips": ["0.0.0.0", "grumble grumble"]})

I only added the first line to have the necessary commands available.

When I run this I receive the following error-message:

/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py:373: UserWarning: ****** WARNING ****** marshmallow_dataclass was called on the class <function NewType.<locals>.new_type at 0x7fb5a077fd90>, which is not a dataclass. It is going to try and convert the class into a dataclass, which may have undesirable side effects. To avoid this message, make sure all your classes and all the classes of their fields are either explicitly supported by marshmallow_dataclass, or define the schema explicitly using field(metadata=dict(marshmallow_field=...)). For more information, see https://github.com/lovasoa/marshmallow_dataclass/issues/51 ****** WARNING ******
warnings.warn(
Traceback (most recent call last):
File "/usr/lib/python3.10/dataclasses.py", line 1197, in fields
    fields = getattr(class_or_instance, _FIELDS)
AttributeError: 'function' object has no attribute '__dataclass_fields__'. Did you mean: '__dataclass_params__'?

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 370, in _internal_class_schema
    fields: Tuple[dataclasses.Field, ...] = dataclasses.fields(clazz)
File "/usr/lib/python3.10/dataclasses.py", line 1199, in fields
    raise TypeError('must be called with a dataclass type or instance')
TypeError: must be called with a dataclass type or instance

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 384, in _internal_class_schema
    created_dataclass: type = dataclasses.dataclass(clazz)
File "/usr/lib/python3.10/dataclasses.py", line 1185, in dataclass
    return wrap(cls)
File "/usr/lib/python3.10/dataclasses.py", line 1176, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash,
File "/usr/lib/python3.10/dataclasses.py", line 909, in _process_class
    for b in cls.__mro__[-1:0:-1]:
AttributeError: 'function' object has no attribute '__mro__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/username/testscript.python", line 9, in <module>
    MyIps.Schema().load({"ips": ["0.0.0.0", "grumble grumble"]})
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/lazy_class_attribute.py", line 33, in __get__
    setattr(cls, self.name, self.func())
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 356, in class_schema
    return _internal_class_schema(clazz, base_schema, clazz_frame)
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 402, in _internal_class_schema
    attributes.update(
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 405, in <genexpr>
    field_for_schema(
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 695, in field_for_schema
    generic_field = _field_for_generic_type(typ, base_schema, typ_frame, **metadata)
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 503, in _field_for_generic_type
    child_type = field_for_schema(
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 729, in field_for_schema
    or _internal_class_schema(typ, base_schema, typ_frame)
File "/home/username/.local/share/virtualenvs/venv_3.10/lib/python3.10/site-packages/marshmallow_dataclass/__init__.py", line 387, in _internal_class_schema
    raise TypeError(
TypeError: IPv4 is not a dataclass and cannot be turned into one.

My current install is python 3.10.6 and marshmallow_dataclasses 8.5.8. (The code was working with python 3.9 and marshmallow dataclasses 8.3.0) Does anyone know why this is happening and how to solve this (other than downgrading, obviously) Does anyone else have this issue? Is this new behaviour and I should adapt our code (if so, how?)? Is this a bug?

Solution

  • I've had a similar issue with a similar bit of code that is raising an error since trying to upgrade marshmallow_dataclasses.

    import dataclasses

import marshmallow_dataclass

ARGON2_PASSWORD = marshmallow_dataclass.NewType(
    "ARGON2_PASSWORD",
    str,
    validate=validate.Regexp(
        r"[$]argon2(?:id|i)[$]v=\d{1,3}[$]m=\d{3,20},t=\d{1,4},"
        r"p=\d{1,2}[$][^$]{1,100}[$][^$]{1,768}"))


@marshmallow_dataclass.add_schema
@dataclasses.dataclass
class Argon2Password:
    password: ARGON2_PASSWORD

    The detailed root cause is currently discussed in https://github.com/lovasoa/marshmallow_dataclass/issues/206 afaics.

    For the time being, downgrading to typing-inspect==0.7.1 worked for me as a hotfix.