[ty] initial support for slots=True in dataclasses#20278
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AlexWaygood merged 1 commit intoastral-sh:mainfrom Sep 7, 2025
Merged
[ty] initial support for slots=True in dataclasses#20278AlexWaygood merged 1 commit intoastral-sh:mainfrom
slots=True in dataclasses#20278AlexWaygood merged 1 commit intoastral-sh:mainfrom
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Diagnostic diff on typing conformance testsChanges were detected when running ty on typing conformance tests--- old-output.txt 2025-09-07 17:09:46.191064468 +0000
+++ new-output.txt 2025-09-07 17:09:48.844087184 +0000
@@ -221,8 +221,6 @@
dataclasses_order.py:50:4: error[unsupported-operator] Operator `<` is not supported for types `DC1` and `DC2`
dataclasses_postinit.py:28:7: error[unresolved-attribute] Type `DC1` has no attribute `x`
dataclasses_postinit.py:29:7: error[unresolved-attribute] Type `DC1` has no attribute `y`
-dataclasses_slots.py:56:1: error[unresolved-attribute] Type `<class 'DC5'>` has no attribute `__slots__`
-dataclasses_slots.py:57:1: error[unresolved-attribute] Type `DC5` has no attribute `__slots__`
dataclasses_slots.py:66:1: error[unresolved-attribute] Type `<class 'DC6'>` has no attribute `__slots__`
dataclasses_slots.py:69:1: error[unresolved-attribute] Type `DC6` has no attribute `__slots__`
dataclasses_transform_class.py:60:8: error[missing-argument] No argument provided for required parameter `not_a_field` of bound method `__init__`
@@ -868,5 +866,5 @@
typeddicts_usage.py:28:1: error[missing-typed-dict-key] Missing required key 'name' in TypedDict `Movie` constructor
typeddicts_usage.py:28:18: error[invalid-key] Invalid key access on TypedDict `Movie`: Unknown key "title"
typeddicts_usage.py:40:24: error[invalid-type-form] The special form `typing.TypedDict` is not allowed in type expressions. Did you mean to use a concrete TypedDict or `collections.abc.Mapping[str, object]` instead?
-Found 869 diagnostics
+Found 867 diagnostics
WARN A fatal error occurred while checking some files. Not all project files were analyzed. See the diagnostics list above for details. |
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slots=True for dataclassesslots=True in dataclasses
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Thanks, this is great! A couple of small points below.
Could you also add something like this test case to https://github.com/astral-sh/ruff/blob/main/crates/ty_python_semantic/resources/mdtest/instance_layout_conflict.md (it already passes on your branch!):
from dataclasses import dataclass
@dataclass(slots=True)
class F: ...
@dataclass(slots=True)
class G: ...
class H(F, G): ... # fine because both classes have empty `__slots__`
@dataclass(slots=True)
class I:
x: int
@dataclass(slots=True)
class J:
y: int
class K(I, J): ... # error: [instance-layout-conflict]And something like this test case to https://github.com/astral-sh/ruff/blob/main/crates/ty_python_semantic/resources/mdtest/type_properties/is_disjoint_from.md (it also already passes on your branch!):
from dataclasses import dataclass
from ty_extensions import is_disjoint_from, static_assert
@dataclass(slots=True)
class F: ...
@dataclass(slots=True)
class G: ...
@dataclass(slots=True)
class I:
x: int
@dataclass(slots=True)
class J:
y: int
# A dataclass with empty `__slots__` is not disjoint from another dataclass with `__slots__`
static_assert(not is_disjoint_from(F, G))
static_assert(not is_disjoint_from(F, I))
static_assert(not is_disjoint_from(G, I))
static_assert(not is_disjoint_from(F, J))
static_assert(not is_disjoint_from(G, J))
# But two dataclasses with non-empty `__slots__` are disjoint
static_assert(is_disjoint_from(I, J))
crates/ty_python_semantic/resources/mdtest/dataclasses/dataclasses.md
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Summary
astral-sh/ty#111
https://docs.python.org/3/library/dataclasses.html
this pr adds initial support for
slots=Truein thedataclassdecorator. synthesizes__slots__as returning a fixed-length tuple ofstrs (field names)Test Plan