[issue35540] dataclasses.asdict breaks with defaultdict fields

2018-12-19 Thread Will T 


New submission from Will T :

_asdict_inner attempts to manually recursively deepcopy dicts by calling 
type(obj) with a generator of transformed keyvalue tuples @ 
https://github.com/python/cpython/blob/b2f642ccd2f65d2f3bf77bbaa103dd2bc2733734/Lib/dataclasses.py#L1080
 . defaultdicts are dicts so this runs but unlike other dicts their first arg 
has to be a callable or None:

import collections
import dataclasses as dc

@dc.dataclass()
class C:
d: dict

c = C(collections.defaultdict(lambda: 3, {}))
d = dc.asdict(c)

assert isinstance(d['d'], collections.defaultdict)
assert d['d']['a'] == 3

=>

Traceback (most recent call last):
  File "boom.py", line 9, in 
d = dc.asdict(c)
  File 
"/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 
1019, in asdict
return _asdict_inner(obj, dict_factory)
  File 
"/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 
1026, in _asdict_inner
value = _asdict_inner(getattr(obj, f.name), dict_factory)
  File 
"/Users/spinlock/.pyenv/versions/3.7.1/lib/python3.7/dataclasses.py", line 
1058, in _asdict_inner
for k, v in obj.items())
TypeError: first argument must be callable or None

I understand that it isn't this bit of code's job to support every dict (and 
list etc.) subclass under the sun but given defaultdict is stdlib it's imo 
worth supporting explicitly.

--
components: Library (Lib)
messages: 332166
nosy: wrmsr
priority: normal
severity: normal
status: open
title: dataclasses.asdict breaks with defaultdict fields
versions: Python 3.7

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[issue32162] typing.Generic breaks __init_subclass__

2018-04-02 Thread Will T 

Will T  added the comment:

I believe I'm experiencing a related bug in the new (3.7) version 
unfortunately. The current version of typing.Generic.__init_subclass__ isn't 
chaining to super(Generic, cls).__init_subclass__, meaning Generic's position 
in class bases can prevent subsequent bases from working properly. I can 
currently work around it with this unsightly hack but it's obviously suboptimal:

_old_generic_init_subclass = object.__getattribute__(ta.Generic, 
'__init_subclass__').__func__
@classmethod  # noqa
def _new_generic_init_subclass(cls, *args, **kwargs):  # noqa
_old_generic_init_subclass(cls, *args, **kwargs)
super(ta.Generic, cls).__init_subclass__(*args, **kwargs)
ta.Generic.__init_subclass__ = _new_generic_init_subclass  # noqa

--
nosy: +wrmsr

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[issue33207] typing.Generic does not correctly call super().__init_subclass__

2018-04-02 Thread Will T 

New submission from Will T :

Per the docs ( 
https://docs.python.org/3/reference/datamodel.html#object.__init_subclass__ ) 
this should be chain-calling super but currently doesn't, and thus breaks base 
classes listed after it which depend on this functionality. Attached a test for 
a real-world usecase of mine. Originally noted in 
https://bugs.python.org/issue32162? but on a new ticket as requested. Thanks :)

--
components: Library (Lib)
files: generic_init_subclass.py
messages: 314828
nosy: wrmsr
priority: normal
severity: normal
status: open
title: typing.Generic does not correctly call super().__init_subclass__
type: behavior
versions: Python 3.7
Added file: https://bugs.python.org/file47513/generic_init_subclass.py

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[issue32162] typing.Generic breaks __init_subclass__

2018-04-02 Thread Will T 

Will T  added the comment:

Done: https://bugs.python.org/issue33207 - thanks for the quick response!

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[issue32873] Pickling of typing types

2018-04-04 Thread Will T 

Will T  added the comment:

I believe I hit a bug with this fix (just pulled the code a few min ago):

In [10]: pickle.loads(pickle.dumps(typing.List))
Out[10]: typing.List

In [11]: pickle.loads(pickle.dumps(typing.FrozenSet))
---
PicklingError Traceback (most recent call last)
 in ()
> 1 pickle.loads(pickle.dumps(typing.FrozenSet))

PicklingError: Can't pickle typing.Frozenset: attribute lookup Frozenset on 
typing failed

The cause is in _GenericAlias.__init__

name = orig_name[0].title() + orig_name[1:]

Maybe just pass the name explicitly?

For context I originally hit this trying to explicitly getattr(typing, 
alias_name) not by pickling but I'm pleased to see that's at least apparently 
intended to be valid use (I need to get the underlying special's parameter 
variance which is lost when you give it args).

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nosy: +wrmsr

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