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stubtest: do not require @disjoint_base if there are __slots__ #19701

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Merged
merged 2 commits into from
Aug 21, 2025
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stubtest: do not require @disjoint_base if there are __slots__ #19701

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stubtest: do not require @disjoint_base if there are __slots__
JelleZijlstra Aug 20, 2025
c4fbcbd
fix with slots
JelleZijlstra Aug 21, 2025
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4 changes: 3 additions & 1 deletion mypy/stubtest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -510,7 +510,9 @@ def _verify_disjoint_base(
if stub.is_final:
return
is_disjoint_runtime = _is_disjoint_base(runtime)
if is_disjoint_runtime and not stub.is_disjoint_base:
# Don't complain about missing @disjoint_base if there are __slots__, because
# in that case we can infer that it's a disjoint base.
if is_disjoint_runtime and not stub.is_disjoint_base and not runtime.__dict__.get("__slots__"):
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@AlexWaygood AlexWaygood Aug 21, 2025 •
edited
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if it's a disjoint base at runtime because it has __slots__, maybe we could change the error message to say "has __slots__ at runtime (making it a disjoint base), but doesn't have __slots__ in the stub"? And ideally tell the user what the __slots__ are at runtime.

Otherwise I worry we'll have contributors adding @disjoint_base to the stubs because a stubtest error message told them to, when actually they should be adding __slots__

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@JelleZijlstra JelleZijlstra Aug 21, 2025

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The code now doesn't make you add @disjoint_base if there are __slots__. Instead stubtest (somewhere else) should just directly tell you to add __slots__.

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@AlexWaygood AlexWaygood Aug 21, 2025

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ohh, I see, sorry! I misread

yield Error(
object_path,
"is a disjoint base at runtime, but isn't marked with @disjoint_base in the stub",
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25 changes: 25 additions & 0 deletions mypy/test/teststubtest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1430,6 +1430,31 @@ class BytesEnum(bytes, enum.Enum):
""",
error=None,
)
yield Case(
stub="""
class HasSlotsAndNothingElse:
__slots__ = ("x",)
x: int

class HasInheritedSlots(HasSlotsAndNothingElse):
pass

class HasEmptySlots:
__slots__ = ()
""",
runtime="""
class HasSlotsAndNothingElse:
__slots__ = ("x",)
x: int

class HasInheritedSlots(HasSlotsAndNothingElse):
pass

class HasEmptySlots:
__slots__ = ()
""",
error=None,
)

@collect_cases
def test_decorator(self) -> Iterator[Case]:
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