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author | Eric V. Smith <ericvsmith@users.noreply.github.com> | 2021-05-03 03:24:53 -0400 |
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committer | GitHub <noreply@github.com> | 2021-05-03 03:24:53 -0400 |
commit | 99ad742ea913e421d012c1a623029eac31bdfe85 (patch) | |
tree | c4645c0b2590b0c8c082986e6fd390ab7304e80c /Lib | |
parent | 72720a2639368436da0981983549d000170623cc (diff) | |
download | cpython-git-99ad742ea913e421d012c1a623029eac31bdfe85.tar.gz |
bpo-44015: dataclasses should allow KW_ONLY to be specified only once per class (GH-25841)
bpo-44015: Raise a TypeError if KW_ONLY is specified more than once.
Diffstat (limited to 'Lib')
-rw-r--r-- | Lib/dataclasses.py | 5 | ||||
-rw-r--r-- | Lib/test/test_dataclasses.py | 77 |
2 files changed, 82 insertions, 0 deletions
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py index 363d0b66d2..cbba320e01 100644 --- a/Lib/dataclasses.py +++ b/Lib/dataclasses.py @@ -930,6 +930,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen, # we can. cls_fields = [] # Get a reference to this module for the _is_kw_only() test. + KW_ONLY_seen = False dataclasses = sys.modules[__name__] for name, type in cls_annotations.items(): # See if this is a marker to change the value of kw_only. @@ -939,6 +940,10 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen, _is_kw_only))): # Switch the default to kw_only=True, and ignore this # annotation: it's not a real field. + if KW_ONLY_seen: + raise TypeError(f'{name!r} is KW_ONLY, but KW_ONLY ' + 'has already been specified') + KW_ONLY_seen = True kw_only = True else: # Otherwise it's a field of some type. diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py index 16ee4c7705..8e645aeb4a 100644 --- a/Lib/test/test_dataclasses.py +++ b/Lib/test/test_dataclasses.py @@ -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: |