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ethanfurman
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gh-105332: [Enum] Fix unpickling flags in edge-cases (GH-105348)
* revert enum pickling from by-name to by-value Co-authored-by: Ethan Furman <[email protected]>
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-23
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4 files changed

+47
-23
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‎Doc/howto/enum.rst

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -517,7 +517,16 @@ from that module.
517517
nested in other classes.
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519519
It is possible to modify how enum members are pickled/unpickled by defining
520-
:meth:`__reduce_ex__` in the enumeration class.
520+
:meth:`__reduce_ex__` in the enumeration class. The default method is by-value,
521+
but enums with complicated values may want to use by-name::
522+
523+
>>> class MyEnum(Enum):
524+
... __reduce_ex__ = enum.pickle_by_enum_name
525+
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.. note::
527+
528+
Using by-name for flags is not recommended, as unnamed aliases will
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not unpickle.
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522531

523532
Functional API

‎Lib/enum.py

Lines changed: 9 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@
1212
'FlagBoundary', 'STRICT', 'CONFORM', 'EJECT', 'KEEP',
1313
'global_flag_repr', 'global_enum_repr', 'global_str', 'global_enum',
1414
'EnumCheck', 'CONTINUOUS', 'NAMED_FLAGS', 'UNIQUE',
15+
'pickle_by_global_name', 'pickle_by_enum_name',
1516
]
1617

1718

@@ -913,7 +914,6 @@ def _convert_(cls, name, module, filter, source=None, *, boundary=None, as_globa
913914
body['__module__'] = module
914915
tmp_cls = type(name, (object, ), body)
915916
cls = _simple_enum(etype=cls, boundary=boundary or KEEP)(tmp_cls)
916-
cls.__reduce_ex__ = _reduce_ex_by_global_name
917917
if as_global:
918918
global_enum(cls)
919919
else:
@@ -1216,7 +1216,7 @@ def __hash__(self):
12161216
return hash(self._name_)
12171217

12181218
def __reduce_ex__(self, proto):
1219-
return getattr, (self.__class__, self._name_)
1219+
return self.__class__, (self._value_, )
12201220

12211221
# enum.property is used to provide access to the `name` and
12221222
# `value` attributes of enum members while keeping some measure of
@@ -1283,8 +1283,14 @@ def _generate_next_value_(name, start, count, last_values):
12831283
return name.lower()
12841284

12851285

1286-
def _reduce_ex_by_global_name(self, proto):
1286+
def pickle_by_global_name(self, proto):
1287+
# should not be used with Flag-type enums
12871288
return self.name
1289+
_reduce_ex_by_global_name = pickle_by_global_name
1290+
1291+
def pickle_by_enum_name(self, proto):
1292+
# should not be used with Flag-type enums
1293+
return getattr, (self.__class__, self._name_)
12881294

12891295
class FlagBoundary(StrEnum):
12901296
"""
@@ -1306,23 +1312,6 @@ class Flag(Enum, boundary=STRICT):
13061312
Support for flags
13071313
"""
13081314

1309-
def __reduce_ex__(self, proto):
1310-
cls = self.__class__
1311-
unknown = self._value_ & ~cls._flag_mask_
1312-
member_value = self._value_ & cls._flag_mask_
1313-
if unknown and member_value:
1314-
return _or_, (cls(member_value), unknown)
1315-
for val in _iter_bits_lsb(member_value):
1316-
rest = member_value & ~val
1317-
if rest:
1318-
return _or_, (cls(rest), cls._value2member_map_.get(val))
1319-
else:
1320-
break
1321-
if self._name_ is None:
1322-
return cls, (self._value_,)
1323-
else:
1324-
return getattr, (cls, self._name_)
1325-
13261315
_numeric_repr_ = repr
13271316

13281317
@staticmethod
@@ -2049,7 +2038,6 @@ def _old_convert_(etype, name, module, filter, source=None, *, boundary=None):
20492038
# unless some values aren't comparable, in which case sort by name
20502039
members.sort(key=lambda t: t[0])
20512040
cls = etype(name, members, module=module, boundary=boundary or KEEP)
2052-
cls.__reduce_ex__ = _reduce_ex_by_global_name
20532041
return cls
20542042

20552043
_stdlib_enums = IntEnum, StrEnum, IntFlag

‎Lib/test/test_enum.py

Lines changed: 27 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,11 @@ def load_tests(loader, tests, ignore):
3131
'../../Doc/library/enum.rst',
3232
optionflags=doctest.ELLIPSIS|doctest.NORMALIZE_WHITESPACE,
3333
))
34+
if os.path.exists('Doc/howto/enum.rst'):
35+
tests.addTests(doctest.DocFileSuite(
36+
'../../Doc/howto/enum.rst',
37+
optionflags=doctest.ELLIPSIS|doctest.NORMALIZE_WHITESPACE,
38+
))
3439
return tests
3540

3641
MODULE = __name__
@@ -66,6 +71,7 @@ class FlagStooges(Flag):
6671
LARRY = 1
6772
CURLY = 2
6873
MOE = 4
74+
BIG = 389
6975
except Exception as exc:
7076
FlagStooges = exc
7177

@@ -74,17 +80,20 @@ class FlagStoogesWithZero(Flag):
7480
LARRY = 1
7581
CURLY = 2
7682
MOE = 4
83+
BIG = 389
7784

7885
class IntFlagStooges(IntFlag):
7986
LARRY = 1
8087
CURLY = 2
8188
MOE = 4
89+
BIG = 389
8290

8391
class IntFlagStoogesWithZero(IntFlag):
8492
NOFLAG = 0
8593
LARRY = 1
8694
CURLY = 2
8795
MOE = 4
96+
BIG = 389
8897

8998
# for pickle test and subclass tests
9099
class Name(StrEnum):
@@ -1942,14 +1951,17 @@ class NEI(NamedInt, Enum):
19421951
__qualname__ = 'NEI'
19431952
x = ('the-x', 1)
19441953
y = ('the-y', 2)
1945-
19461954
self.assertIs(NEI.__new__, Enum.__new__)
19471955
self.assertEqual(repr(NEI.x + NEI.y), "NamedInt('(the-x + the-y)', 3)")
19481956
globals()['NamedInt'] = NamedInt
19491957
globals()['NEI'] = NEI
19501958
NI5 = NamedInt('test', 5)
19511959
self.assertEqual(NI5, 5)
19521960
self.assertEqual(NEI.y.value, 2)
1961+
with self.assertRaisesRegex(TypeError, "name and value must be specified"):
1962+
test_pickle_dump_load(self.assertIs, NEI.y)
1963+
# fix pickle support and try again
1964+
NEI.__reduce_ex__ = enum.pickle_by_enum_name
19531965
test_pickle_dump_load(self.assertIs, NEI.y)
19541966
test_pickle_dump_load(self.assertIs, NEI)
19551967

@@ -3252,11 +3264,17 @@ def test_pickle(self):
32523264
test_pickle_dump_load(self.assertEqual,
32533265
FlagStooges.CURLY&~FlagStooges.CURLY)
32543266
test_pickle_dump_load(self.assertIs, FlagStooges)
3267+
test_pickle_dump_load(self.assertEqual, FlagStooges.BIG)
3268+
test_pickle_dump_load(self.assertEqual,
3269+
FlagStooges.CURLY|FlagStooges.BIG)
32553270

32563271
test_pickle_dump_load(self.assertIs, FlagStoogesWithZero.CURLY)
32573272
test_pickle_dump_load(self.assertEqual,
32583273
FlagStoogesWithZero.CURLY|FlagStoogesWithZero.MOE)
32593274
test_pickle_dump_load(self.assertIs, FlagStoogesWithZero.NOFLAG)
3275+
test_pickle_dump_load(self.assertEqual, FlagStoogesWithZero.BIG)
3276+
test_pickle_dump_load(self.assertEqual,
3277+
FlagStoogesWithZero.CURLY|FlagStoogesWithZero.BIG)
32603278

32613279
test_pickle_dump_load(self.assertIs, IntFlagStooges.CURLY)
32623280
test_pickle_dump_load(self.assertEqual,
@@ -3266,11 +3284,19 @@ def test_pickle(self):
32663284
test_pickle_dump_load(self.assertEqual, IntFlagStooges(0))
32673285
test_pickle_dump_load(self.assertEqual, IntFlagStooges(0x30))
32683286
test_pickle_dump_load(self.assertIs, IntFlagStooges)
3287+
test_pickle_dump_load(self.assertEqual, IntFlagStooges.BIG)
3288+
test_pickle_dump_load(self.assertEqual, IntFlagStooges.BIG|1)
3289+
test_pickle_dump_load(self.assertEqual,
3290+
IntFlagStooges.CURLY|IntFlagStooges.BIG)
32693291

32703292
test_pickle_dump_load(self.assertIs, IntFlagStoogesWithZero.CURLY)
32713293
test_pickle_dump_load(self.assertEqual,
32723294
IntFlagStoogesWithZero.CURLY|IntFlagStoogesWithZero.MOE)
32733295
test_pickle_dump_load(self.assertIs, IntFlagStoogesWithZero.NOFLAG)
3296+
test_pickle_dump_load(self.assertEqual, IntFlagStoogesWithZero.BIG)
3297+
test_pickle_dump_load(self.assertEqual, IntFlagStoogesWithZero.BIG|1)
3298+
test_pickle_dump_load(self.assertEqual,
3299+
IntFlagStoogesWithZero.CURLY|IntFlagStoogesWithZero.BIG)
32743300

32753301
def test_contains_tf(self):
32763302
Open = self.Open

‎Misc/NEWS.d/next/Library/2023-06-06-11-50-33.gh-issue-105332.tmpgRA.rst

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
Revert pickling method from by-name back to by-value.

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