default_factory field fails with inherited stdlib dataclass

[ahirner]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.8
            pydantic compiled: True
                 install path: /Users/dafcok/miniconda3/lib/python3.6/site-packages/pydantic
               python version: 3.6.8 |Anaconda, Inc.| (default, Dec 29 2018, 19:04:46)  [GCC 4.2.1 Compatible Clang 4.0.1 (tags/RELEASE_401/final)]
                     platform: Darwin-19.6.0-x86_64-i386-64bit
     optional deps. installed: ['devtools', 'dotenv', 'email-validator', 'typing-extensions'

$ pip freeze |grep 'dataclasses\|typing'
dataclasses==0.8
typing==3.6.6
typing-extensions==3.7.4.3

from dataclasses import dataclass, field

from pydantic.dataclasses import dataclass as validated_dataclass

@dataclass
class Base:
    x: str

# doesn't fail
@dataclass
class Thing(Base):
    y: str = field(default_factory=str)

# fails
@validated_dataclass
class ValidatedThing(Base):
    y: str = field(default_factory=str)

dataclasses tries to delete y attribute which isn't set.

tests/test_resources.py:12: in <module>
    class ValidatedThing(Base):
pydantic/dataclasses.py:255: in pydantic.dataclasses.dataclass
    ???
pydantic/dataclasses.py:250: in pydantic.dataclasses.dataclass.wrap
    ???
pydantic/dataclasses.py:158: in pydantic.dataclasses._process_class
    ???
~/lib/python3.6/site-packages/dataclasses.py:958: in dataclass
    return wrap(_cls)
~/lib/python3.6/site-packages/dataclasses.py:950: in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
~/lib/python3.6/site-packages/dataclasses.py:817: in _process_class
    delattr(cls, f.name)
E   AttributeError: y

Also fails on 1.7.1 but not on 1.7. Any ideas? I'd be happy to author a fix.

[ahirner]

@PrettyWood What's your take on tackling this issue? AFAICS one has to dig deeper into dynamic type creation from there.

[PrettyWood]

@ahirner Please have a look at the linked PR. I forgot to add this issue to the list ;)

[troiganto]

Any development on this? I am currently evaluating pydantic for a project and ran into this issue myself.

Minimal reproduction:

import dataclasses as dc
import typing as t
import pydantic

print(pydantic.utils.version_info())

@pydantic.dataclasses.dataclass
class Example:
    count: int = pydantic.Field(0)
    names: t.List[str] = pydantic.Field(default_factory=list)
print(Example())

@dc.dataclass
class Example:
    count: int = dc.field(default=0)
    names: t.List[str] = dc.field(default_factory=list)
print(Example())

Example = pydantic.dataclasses.dataclass(Example)
print(Example())

Output:

             pydantic version: 1.9.0
            pydantic compiled: True
                 install path: /opt/venvs/default/lib/python3.7/site-packages/pydantic
               python version: 3.7.10 (default, Mar 30 2022, 21:45:23)  [GCC 12.0.1 20220308 (Red Hat 12.0.1-0)]
                     platform: Linux-5.17.1-300.fc36.x86_64-x86_64-with-fedora-36-Thirty_Six
     optional deps. installed: ['typing-extensions']
Example(count=0, names=[])
Example(count=0, names=[])
Traceback (most recent call last):
  File "pydantic_test.py", line 19, in <module>
    Example = pydantic.dataclasses.dataclass(Example)
  File "pydantic/dataclasses.py", line 255, in pydantic.dataclasses.dataclass
    f'repr={self.repr!r},'
  File "pydantic/dataclasses.py", line 250, in pydantic.dataclasses.dataclass.wrap
    f'name={self.name!r},'
  File "pydantic/dataclasses.py", line 159, in pydantic.dataclasses._process_class
    # in the function signature of dataclasses' constructors.
  File "/opt/pyenv/versions/3.7.10/lib/python3.7/dataclasses.py", line 1010, in dataclass
    return wrap(_cls)
  File "/opt/pyenv/versions/3.7.10/lib/python3.7/dataclasses.py", line 1002, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "/opt/pyenv/versions/3.7.10/lib/python3.7/dataclasses.py", line 921, in _process_class
    globals,
  File "/opt/pyenv/versions/3.7.10/lib/python3.7/dataclasses.py", line 491, in _init_fn
    raise TypeError(f'non-default argument {f.name!r} '
TypeError: non-default argument 'names' follows default argument

I've already confirmed that #2557 fixes this issue. Using that PR, the output is as expected:

             pydantic version: 1.9.0a1
            pydantic compiled: False
                 install path: /opt/venvs/default/lib/python3.7/site-packages/pydantic
               python version: 3.7.10 (default, Mar 30 2022, 21:45:23)  [GCC 12.0.1 20220308 (Red Hat 12.0.1-0)]
                     platform: Linux-5.17.1-300.fc36.x86_64-x86_64-with-fedora-36-Thirty_Six
     optional deps. installed: ['typing-extensions']
Example(count=0, names=[])
Example(count=0, names=[])
Example(count=0, names=[])

I've further confirmed that the snippet in the original post runs successfully with the PR but fails on published Pydantic 1.9.0.

[samuelcolvin]

@troiganto looks like this is still an issue. I'll be something deep in the way we convert dataclasses.

[PrettyWood]

@samuelcolvin #2557 fixes this issue. I'll try to work again on this so we can merge it for v1.10