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[3.12] gh-116040: [Enum] fix by-value calls when second value is fals…
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…ey (GH-116072) (GH-116476)

e.g. Cardinal(1, 0)

(cherry picked from commit 13ffd4b)
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ethanfurman authored Mar 7, 2024
1 parent 4efd20e commit d771729
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Showing 3 changed files with 46 additions and 4 deletions.
15 changes: 11 additions & 4 deletions Lib/enum.py
Original file line number Diff line number Diff line change
Expand Up @@ -166,6 +166,13 @@ def _dedent(text):
lines[j] = l[i:]
return '\n'.join(lines)

class _not_given:
def __repr__(self):
return('<not given>')
def __bool__(self):
return False
_not_given = _not_given()

class _auto_null:
def __repr__(self):
return '_auto_null'
Expand Down Expand Up @@ -718,7 +725,7 @@ def __bool__(cls):
"""
return True

def __call__(cls, value, names=None, *values, module=None, qualname=None, type=None, start=1, boundary=None):
def __call__(cls, value, names=_not_given, *values, module=None, qualname=None, type=None, start=1, boundary=None):
"""
Either returns an existing member, or creates a new enum class.
Expand Down Expand Up @@ -747,18 +754,18 @@ def __call__(cls, value, names=None, *values, module=None, qualname=None, type=N
"""
if cls._member_map_:
# simple value lookup if members exist
if names:
if names is not _not_given:
value = (value, names) + values
return cls.__new__(cls, value)
# otherwise, functional API: we're creating a new Enum type
if names is None and type is None:
if names is _not_given and type is None:
# no body? no data-type? possibly wrong usage
raise TypeError(
f"{cls} has no members; specify `names=()` if you meant to create a new, empty, enum"
)
return cls._create_(
class_name=value,
names=names,
names=names or None,
module=module,
qualname=qualname,
type=type,
Expand Down
34 changes: 34 additions & 0 deletions Lib/test/test_enum.py
Original file line number Diff line number Diff line change
Expand Up @@ -3312,6 +3312,40 @@ def __new__(cls, value):
member._value_ = Base(value)
return member

def test_second_tuple_item_is_falsey(self):
class Cardinal(Enum):
RIGHT = (1, 0)
UP = (0, 1)
LEFT = (-1, 0)
DOWN = (0, -1)
self.assertIs(Cardinal(1, 0), Cardinal.RIGHT)
self.assertIs(Cardinal(-1, 0), Cardinal.LEFT)

def test_no_members(self):
with self.assertRaisesRegex(
TypeError,
'has no members',
):
Enum(7)
with self.assertRaisesRegex(
TypeError,
'has no members',
):
Flag(7)

def test_empty_names(self):
for nothing, e_type in (
('', None),
('', int),
([], None),
([], int),
({}, None),
({}, int),
):
empty_enum = Enum('empty_enum', nothing, type=e_type)
self.assertEqual(len(empty_enum), 0)
self.assertRaises(TypeError, 'has no members', empty_enum, 0)


class TestOrder(unittest.TestCase):
"test usage of the `_order_` attribute"
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
[Enum] fix by-value calls when second value is falsey; e.g. Cardinal(1, 0)

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