decorators only when __debug__ == True

[Stephen Hansen]

On 2010-03-31 13:59:01 -0700, LX said:
>> pass_decorator will be called when the decorated function is _defined_,
>> but not when the decorated function is _called_.
> 
> Why is it then that during runtime, with a breakpoint in some
> arbitrary main() in main.py, I get something similar to the following
> call stack:
> 
> main.py, line xxx, in <module>
>  main()
> 
> <string>, line 2, in main
> 
> decorator.py, line 261, in pass_decorator
>  return f(*args, **kw)
> 
> main.py, line yyy, in main()
>  * breakpoint line here *
> 
> It looks to me the call stack still includes the additional level of
> the decorator... what am I missing? Thank you for your time.

You're not defining pass_decorator correctly. Always show us the actual 
code when you're showing results.

Your pass_decorator should just return the original function, 
undecorated, unmodified if you're not in debug. It should only return a 
decorated function otherwise.

Consider:

-----
from decorator import decorator

def debug_decorator(fn):
    if __debug__:
        def wrapper(fn, *args, **kwargs):
            # insert pre-condition testing here
            if len(args) != 1:
                raise ValueError("Incorrect number of arguments")

            result = fn(*args, **kwargs)

            # insert post-condition testing here
            if result not in (True, False):
                raise ValueError("Incorrect return value!")

            return result
        return decorator(wrapper, fn)
    else:
        return fn

@debug_decorator
def my_test(arg):
    if not arg:
        raise RuntimeError
    return True

my_test(0)
-----

And the output depending on if you're in debug mode or not:
Top:test ixokai$ python deco.py
Traceback (most recent call last):
  File "deco.py", line 27, in <module>
    my_test(0)
  File "<string>", line 2, in my_test
  File "deco.py", line 10, in wrapper
    result = fn(*args, **kwargs)
  File "deco.py", line 24, in my_test
    raise RuntimeError
RuntimeError

Top:test ixokai$ python -O deco.py
Traceback (most recent call last):
  File "deco.py", line 27, in <module>
    my_test(0)
  File "deco.py", line 24, in my_test
    raise RuntimeError
RuntimeError


-- 
--S

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