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bpo-44015: dataclasses should allow KW_ONLY to be specified only once per class (GH-25841)

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bpo-44015: Raise a TypeError if KW_ONLY is specified more than once.
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Eric V. Smith 2021-05-03 03:24:53 -04:00 • committed by GitHub
parent 72720a2639
commit 99ad742ea9
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3 changed files with 83 additions and 0 deletions
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77
Lib/test/test_dataclasses.py
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@ -3699,6 +3699,83 @@ class TestKeywordArgs(unittest.TestCase):
self.assertEqual(c.b, 3)
self.assertEqual(c.c, 2)
def test_KW_ONLY_as_string(self):
@dataclass
class A:
a: int
_: 'dataclasses.KW_ONLY'
b: int
c: int
A(3, c=5, b=4)
msg = "takes 2 positional arguments but 4 were given"
with self.assertRaisesRegex(TypeError, msg):
A(3, 4, 5)
def test_KW_ONLY_twice(self):
msg = "'Y' is KW_ONLY, but KW_ONLY has already been specified"
with self.assertRaisesRegex(TypeError, msg):
@dataclass
class A:
a: int
X: KW_ONLY
Y: KW_ONLY
b: int
c: int
with self.assertRaisesRegex(TypeError, msg):
@dataclass
class A:
a: int
X: KW_ONLY
b: int
Y: KW_ONLY
c: int
with self.assertRaisesRegex(TypeError, msg):
@dataclass
class A:
a: int
X: KW_ONLY
b: int
c: int
Y: KW_ONLY
# But this usage is okay, since it's not using KW_ONLY.
@dataclass
class A:
a: int
_: KW_ONLY
b: int
c: int = field(kw_only=True)
# And if inheriting, it's okay.
@dataclass
class A:
a: int
_: KW_ONLY
b: int
c: int
@dataclass
class B(A):
_: KW_ONLY
d: int
# Make sure the error is raised in a derived class.
with self.assertRaisesRegex(TypeError, msg):
@dataclass
class A:
a: int
_: KW_ONLY
b: int
c: int
@dataclass
class B(A):
X: KW_ONLY
d: int
Y: KW_ONLY
def test_post_init(self):
@dataclass
class A: