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Reimplement function with_metaclass()

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Mathias J. Hennig 2015-07-22 23:35:13 +02:00
parent ac12e362c4
commit c8f19f0afc
1 changed files with 4 additions and 12 deletions
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16
flask/_compat.py
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@ -56,21 +56,13 @@ else:
def with_metaclass(meta, *bases): def with_metaclass(meta, *bases):
# This requires a bit of explanation: the basic idea is to make a # This requires a bit of explanation: the basic idea is to make a
# dummy metaclass for one level of class instantiation that replaces # dummy metaclass for one level of class instantiation that replaces
# itself with the actual metaclass. Because of internal type checks # itself with the actual metaclass.
# we also need to make sure that we downgrade the custom metaclass
# for one level to something closer to type (that's why __call__ and
# __init__ comes back from type etc.).
# #
# This has the advantage over six.with_metaclass in that it does not # This has the advantage over six.with_metaclass in that it does not
# introduce dummy classes into the final MRO. # introduce dummy classes into the final MRO.
class metaclass(meta): constructor = lambda c, name, b, dct: meta(name, bases, dct)
__call__ = type.__call__ metaclass = type('with_metaclass', (type,), {'__new__': constructor})
__init__ = type.__init__ return type.__new__(metaclass, 'temporary_class', (object,), {})
def __new__(cls, name, this_bases, d):
if this_bases is None:
return type.__new__(cls, name, (), d)
return meta(name, bases, d)
return metaclass('temporary_class', None, {})
# Certain versions of pypy have a bug where clearing the exception stack # Certain versions of pypy have a bug where clearing the exception stack