[issue44003] functools.lru_cache omits __defaults__ attribute from wrapped function

[Gregory P. Smith]

Gregory P. Smith <greg at krypto.org> added the comment:

That was anecdotal evidence:

```
Python 3.9.1 (v3.9.1:1e5d33e9b9, Dec  7 2020, 12:10:52) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> def func(arg=1, *, kwarg=2): pass
... 
>>> import functools
>>> from functools import lru_cache, update_wrapper
>>> @lru_cache
... def cached_func(arg=1, *, kwargs=2): pass
... 
>>> def x(*args, **kwargs): func(*args, **kwargs)
... 
>>> updated_x = update_wrapper(func, x)
>>> x
<function x at 0x7feff5892b80>
>>> updated_x
<function x at 0x7feff5828a60>
>>> updated_x.__defaults__
(1,)
>>> updated_x.__kwdefaults__
{'kwarg': 2}
>>> func.__defaults__
(1,)
>>> func.__kwdefaults__
{'kwarg': 2}
>>> cached_func.__defaults__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'functools._lru_cache_wrapper' object has no attribute '__defaults__'
>>> cached_func.__kwdefaults__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'functools._lru_cache_wrapper' object has no attribute '__kwdefaults__'
```

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue44003>
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