[issue42455] Add decorator_with_params function to functools module

[Yurii Karabas]

Yurii Karabas <1998uri...@gmail.com> added the comment:

I agree, decorator factory definitely a better name

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[issue42455] Add decorator_with_params function to functools module

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

I would call it decorator_factory.

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nosy: +serhiy.storchaka

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[issue42455] Add decorator_with_params function to functools module

[Yurii Karabas]

Yurii Karabas <1998uri...@gmail.com> added the comment:

Add Raymond Hettinger because he is at `Expert Index` for `functools` module

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nosy: +rhettinger

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[issue42455] Add decorator_with_params function to functools module

[Yurii Karabas]

Change by Yurii Karabas <1998uri...@gmail.com>:


--
keywords: +patch
pull_requests: +22390
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/23501

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[issue42455] Add decorator_with_params function to functools module

[Yurii Karabas]

New submission from Yurii Karabas <1998uri...@gmail.com>:

In the current python codebases, there are a lot of decorators with parameters, 
and their code in most cases contains a lot of code boilerplates. The purpose 
of this issue is to add `decorator_with_params` function to `functools` module. 
This function will allow using a wrapped function as a simple decorator and 
decorator with parameter. 

I believe the real example will bring more context, for instance, 
`typing._tp_cache` function can be rewritten from:
```
def _tp_cache(func=None, /, *, typed=False):
"""Internal wrapper caching __getitem__ of generic types with a fallback to
original function for non-hashable arguments.
"""
def decorator(func):
cached = functools.lru_cache(typed=typed)(func)
_cleanups.append(cached.cache_clear)

@functools.wraps(func)
def inner(*args, **kwds):
try:
return cached(*args, **kwds)
except TypeError:
pass
return func(*args, **kwds)
return inner

if func is not None:
return decorator(func)

return decorator
```
To
```
@decorator_with_params
def _tp_cache(func=None, /, *, typed=False):
"""Internal wrapper caching __getitem__ of generic types with a fallback to
original function for non-hashable arguments.
"""
cached = functools.lru_cache(typed=typed)(func)
_cleanups.append(cached.cache_clear)

@functools.wraps(func)
def inner(*args, **kwds):
try:
return cached(*args, **kwds)
except TypeError:
pass  # All real errors (not unhashable args) are raised below.
return func(*args, **kwds)

return inner
```

And `_tp_cache` can be used as:
```
@_tp_cache(typed=True)
def __getitem__(self, parameters):
return self._getitem(self, parameters)
...
@_tp_cache
def __getitem__(self, parameters):
return self._getitem(self, parameters)
```

Proposed implementation is quite simple (I used it in a lot of projects):
```
def decorator_with_params(deco):
@wraps(deco)
def decorator(func=None, /, *args, **kwargs):
if func is not None:
return deco(func, *args, **kwargs)

def wrapper(f):
return deco(f, *args, **kwargs)

return wrapper

return decorator
```

I believe it will be a great enhancement for the Python standard library and 
will save such important indentations.

--
components: Library (Lib)
messages: 381773
nosy: uriyyo
priority: normal
severity: normal
status: open
title: Add decorator_with_params function to functools module
type: enhancement
versions: Python 3.10

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