gh-93910: Fix enum performance regression (GH-94614)

This removes the performance regression in 3.11, **at the expense of not fixing
the "bug" that allows accessing values from values** (e.g. `Color.RED.BLUE`).

Using the benchmark @markshannon [presented](https://github.com/python/cpython/issues/93910#issuecomment-1165503032), the results are:

| Version | Enum | Fast enum | Normal class |
| --- | --- | --- | --- |
| 3.10 | 2.04 | 0.59 | 0.56 |
| 3.11 | 2.78 | 0.31 | 0.15 |
| This PR | 1.30 | 0.32 | 0.16 |

I share this mostly as information about the source of the regression, as this may be useful. It may be that the lower-risk approach for the beta is just to revert to a previously-known working state.
This commit is contained in:
Michael Droettboom 2022-07-07 07:26:56 -04:00 committed by GitHub
parent 277f55cb04
commit ed136b9673
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3 changed files with 13 additions and 8 deletions

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@ -309,16 +309,17 @@ class _proto_member:
if descriptor and not need_override:
# previous enum.property found, no further action needed
pass
else:
elif descriptor and need_override:
redirect = property()
redirect.__set_name__(enum_class, member_name)
if descriptor and need_override:
# previous enum.property found, but some other inherited attribute
# is in the way; copy fget, fset, fdel to this one
redirect.fget = descriptor.fget
redirect.fset = descriptor.fset
redirect.fdel = descriptor.fdel
# Previous enum.property found, but some other inherited attribute
# is in the way; copy fget, fset, fdel to this one.
redirect.fget = descriptor.fget
redirect.fset = descriptor.fset
redirect.fdel = descriptor.fdel
setattr(enum_class, member_name, redirect)
else:
setattr(enum_class, member_name, enum_member)
# now add to _member_map_ (even aliases)
enum_class._member_map_[member_name] = enum_member
try:
@ -647,7 +648,7 @@ class EnumType(type):
'member order does not match _order_:\n %r\n %r'
% (enum_class._member_names_, _order_)
)
#
return enum_class
def __bool__(cls):

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@ -2646,6 +2646,7 @@ class TestSpecial(unittest.TestCase):
self.assertEqual(Private._Private__corporal, 'Radar')
self.assertEqual(Private._Private__major_, 'Hoolihan')
@unittest.skip("Accessing all values retained for performance reasons, see GH-93910")
def test_exception_for_member_from_member_access(self):
with self.assertRaisesRegex(AttributeError, "<enum .Di.> member has no attribute .NO."):
class Di(Enum):

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@ -0,0 +1,3 @@
The ability to access the other values of an enum on an enum (e.g.
``Color.RED.BLUE``) has been restored in order to fix a performance
regression.