LocalProxy: add __wrapped__ attribute to refer to wrapped function

[immerrr]

This is an attempt to fix pallets/flask#1680.

__wrapped__ attribute is a somewhat unofficial dunder-attribute used in functools and inspect to refer to an underlying function of a decorator. Technically, LocalProxy can wrap callables, so using __wrapped__ attribute does not seem much of a "workaround".

If "local" is not a callable, __wrapped__ slot is not initialized, and thus the proxy.__wrapped__ request will be forwarded to current object as previously.

[RonnyPfannschmidt]

looks nice to me, can you please extend it with a unit-test for both simple cases as this is basically a new feature changing the external interface of the locals

[immerrr]

@RonnyPfannschmidt done!

[RonnyPfannschmidt]

looks good to me :)

i'd like another pair of eyes on it to be sure these are the semantics we should add to werkzeug
and what kind of release it needs

locals are very important and while this change looks very useful i'd like to avoid unwarranted disruption

[untitaker]

LGTM, and I'm surprised the fix is so straightforward and that there exists a good reasoning that those are correct semantics instead of a hack. Nice job.

• Do the tests fail properly without the fix? (use git checkout HEAD^1 werkzeug to revert just the fix).
• Should this be part of a bugfix release?

[immerrr]

Do the tests fail properly without the fix?

Yes,

=================================== FAILURES ===================================
______________________ test_local_proxy_wrapped_attribute ______________________

    def test_local_proxy_wrapped_attribute():
        class SomeClassWithWrapped(object):
            __wrapped__ = 'wrapped'

        def lookup_func():
            return 42

        partial_lookup_func = partial(lookup_func)

        proxy = local.LocalProxy(lookup_func)
>       assert proxy.__wrapped__ is lookup_func

tests/test_local.py:197: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = 42, name = '__wrapped__'

    def __getattr__(self, name):
        if name == '__members__':
            return dir(self._get_current_object())
>       return getattr(self._get_current_object(), name)
E       AttributeError: 'int' object has no attribute '__wrapped__'

werkzeug/local.py:343: AttributeError
=============== 1 failed, 429 passed, 30 skipped in 1.35 seconds ===============

[untitaker]

Excellent, thank you!

[xrmx]

@untitaker Any chance this can be backported to 0.11 please?

[untitaker]

Sorry, but I don't consider this to be a bugfix as it originally was never
intended to work that way.

On Sun, Jul 31, 2016 at 07:03:51AM -0700, Riccardo Magliocchetti wrote:

@untitaker Any chance this can be backported to 0.11 please?

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