[issue3445] Ignore missing attributes in functools.update_wrapper

[Russell Keith-Magee]

Russell Keith-Magee <freakboy3742 at gmail.com> added the comment:

As an extra data point: we just hit this problem in Django ticket #13093 (http://code.djangoproject.com/ticket/13093). In our case, a decorator was using wraps(); however, that decorator was breaking when it was used on a class with a __call__ method, because the instance of the class doesn't have a __name__ attribute. 

We've implemented the proposed workaround (i.e., check the attributes that are available and provide that tuple as the assigned argument), but I don't agree that this should be expected behavior. wraps() is used to make a decorated callable look like the callable that is being decorated; if there are different types of callable objects, I would personally expect wraps() to adapt to the differences, not raise an error if it sees anything other than a function. 

True, some attributes (like __doc__) won't always be correct as a result of wrapping on non-vanilla functions -- but then, that's true of plain vanilla functions, too. A decorator wrapping a function can fundamentally change what the wrapped function does, and there's no guarantee that the docstring for the wrapped function will still be correct after decoration.

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nosy: +freakboy3742
versions: +Python 2.5, Python 2.6

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<http://bugs.python.org/issue3445>
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