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gh-119581: Add a test of InitVar with name shadowing #119582

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merged 2 commits into from
May 28, 2024
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gh-119581: Add a test of InitVar with name shadowing #119582

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[gh-119581] Add a test of InitVar with name shadowing
stroxler May 26, 2024
422d417
Update Lib/test/test_dataclasses/__init__.py
stroxler May 28, 2024
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23 changes: 23 additions & 0 deletions Lib/test/test_dataclasses/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1317,6 +1317,29 @@ def __post_init__(self, init_base, init_derived):
c = C(10, 11, 50, 51)
self.assertEqual(vars(c), {'x': 21, 'y': 101})

def test_init_var_name_shadowing(self):
# Because dataclasses rely exclusively on `__annotations__` for
# handling InitVar and `__annotations__` preserves shadowed definitions,
# you can actually shadow an InitVar with a method or property.
#
# This only works when there is no default value; `dataclasses` uses the
# actual name (which will be bound to the shadowing method) for default
# values.
@dataclass
class C:
shadowed: InitVar[int]
_shadowed: int = field(init=False)

def __post_init__(self, shadowed):
self._shadowed = shadowed * 2

@property
def shadowed(self):
return self._shadowed * 3

c = C(5)
self.assertEqual(c.shadowed, 30)

def test_default_factory(self):
# Test a factory that returns a new list.
@dataclass
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