[Python-Dev] Adding functools.decorator

[Nick Coghlan]

Collin Winters has done the work necessary to rename PEP 309's functional 
module to functools and posted the details to SF [1].

I'd like to take that patch, tweak it so the C module is built as _functools 
rather than functools, and then add a functools.py consisting of:

from _functools import * # Pick up functools.partial

def _update_wrapper(decorated, func, deco_func):
     # Support naive introspection
     decorated.__module__ = func.__module__
     decorated.__name__ = func.__name__
     decorated.__doc__ = func.__doc__
     decorated.__dict__.update(func.__dict__)
     # Provide access to decorator and original function
     decorated.__decorator__ = deco_func
     decorated.__decorates__ = func

def decorator(deco_func):
     """Wrap a function as an introspection friendly decorator function"""
     def wrapper(func):
         decorated = deco_func(func)
         if decorated is func:
             return func
         _update_wrapper(decorated, func, deco_func)
         return decorated
     # Manually make this decorator introspection friendly
     _update_wrapper(wrapper, deco_func, decorator)
     return wrapper

After typing those four lines of boilerplate to support naive introspection 
out in full several times for contextlib related decorators, I can testify 
that doing it by hand gets old really fast :)

Some details that are up for discussion:

   - which of a function's special attributes should be copied/updated?
   - should the __decorates__ and __decorator__ attributes be added?

If people are happy with this idea, I can make sure it happens before alpha 3.

Cheers,
Nick.

[1] http://www.python.org/sf/1478788


-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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