New submission from Veith Röthlingshöfer <veit...@gmail.com>:
When creating a dataclass with a default that is a field with a default
factory, the factory is not correctly resolved in cls.__init__.__defaults__. It
evaluates to the __repr__ of dataclasses._HAS_DEFAULT_FACTORY_CLASS, which is
"<factory>".
The expected behavior would be to have a value of whatever the default factory
produces as a default.
This causes issues for example when using
inspect.BoundParameters.apply_defaults() on the __init__ of such a dataclass.
Code to reproduce:
```
from dataclasses import dataclass, field
from typing import Any, Dict
@dataclass()
class Test:
a: int
b: Dict[Any, Any] = field(default_factory=dict)
print(Test.__init__.__defaults__) # <factory>
```
The affected packages are on a high-level dataclasses, on a lower level the
issue is in the builtin __function.__defaults__.
----------
components: C API
messages: 358562
nosy: RunOrVeith
priority: normal
severity: normal
status: open
title: __function.__defaults__ breaks for __init__ of dataclasses with default
factory
type: behavior
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue39078>
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