[issue13266] Add inspect.unwrap(f) to easily unravel "__wrapped__" chains

[Nick Coghlan]

Nick Coghlan added the comment:

Turns out there's a bug in the implementation of functools.update_wrapper :P

Added that as a dependency, since this API doesn't make sense until update_wrapper is behaving itself.

The new tests didn't pick it up because they don't use wraps or update_wrapper, they set __wrapped__ directly.

Also, the replacement of the recursion in inspect.signature is incorrect - we want to interleave checks for __signature__ as we recurse through the stack of wrapper functions.

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dependencies: +functools.update_wrapper mishandles __wrapped__

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<http://bugs.python.org/issue13266>
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