add the module path to the mangled name of an internal dataclass symbol

Author: tyralla

mypy/plugins/dataclasses.py

@@ -91,8 +91,8 @@
     frozen_default=False,
     field_specifiers=DATACLASS_FIELD_SPECIFIERS,
 )
-_INTERNAL_REPLACE_SYM_NAME: Final = "__mypy-replace"
-_INTERNAL_POST_INIT_SYM_NAME: Final = "__mypy-post_init"
+_INTERNAL_REPLACE_SYM_NAME: Final = "mypy-replace"
+_INTERNAL_POST_INIT_SYM_NAME: Final = "mypy-post_init"
 
 
 class DataclassAttribute:
@@ -422,7 +422,7 @@ def _add_internal_replace_method(self, attributes: list[DataclassAttribute]) ->
         Stashes the signature of 'dataclasses.replace(...)' for this specific dataclass
         to be used later whenever 'dataclasses.replace' is called for this dataclass.
         """
-        mangled_name = f"_{self._cls.name.lstrip('_')}{_INTERNAL_REPLACE_SYM_NAME}"
+        mangled_name = _mangle_internal_sym_name(self._cls.fullname, _INTERNAL_REPLACE_SYM_NAME)
         add_method_to_class(
             self._api,
             self._cls,
@@ -433,7 +433,7 @@ def _add_internal_replace_method(self, attributes: list[DataclassAttribute]) ->
         )
 
     def _add_internal_post_init_method(self, attributes: list[DataclassAttribute]) -> None:
-        mangled_name = f"_{self._cls.name.lstrip('_')}{_INTERNAL_POST_INIT_SYM_NAME}"
+        mangled_name = _mangle_internal_sym_name(self._cls.fullname, _INTERNAL_POST_INIT_SYM_NAME)
         add_method_to_class(
             self._api,
             self._cls,
@@ -971,6 +971,15 @@ def dataclass_class_maker_callback(ctx: ClassDefContext) -> bool:
     return transformer.transform()
 
 
+def _mangle_internal_sym_name(type_fullname: str, member_name: str) -> str:
+    """Create an internal symbol name with the class name mangled in as usual, but that also
+    contains the class module path to avoid false positives when subclassing a dataclass with
+    same name."""
+    module_name, type_name = type_fullname.rsplit(".")
+    module_name = module_name.replace(".", "-")
+    type_name = type_name.lstrip('_')
+    return f"_{type_name}__{module_name}__{member_name}"
+
 def _get_transform_spec(reason: Expression) -> DataclassTransformSpec:
     """Find the relevant transform parameters from the decorator/parent class/metaclass that
     triggered the dataclasses plugin.
@@ -1029,7 +1038,7 @@ def _get_expanded_dataclasses_fields(
             ctx, get_proper_type(typ.upper_bound), display_typ, parent_typ
         )
     elif isinstance(typ, Instance):
-        mangled_name = f"_{typ.type.name.lstrip('_')}{_INTERNAL_REPLACE_SYM_NAME}"
+        mangled_name = _mangle_internal_sym_name(typ.type.fullname, _INTERNAL_REPLACE_SYM_NAME)
         replace_sym = typ.type.get_method(mangled_name)
         if replace_sym is None:
             return None
@@ -1114,7 +1123,7 @@ def check_post_init(api: TypeChecker, defn: FuncItem, info: TypeInfo) -> None:
         return
     assert isinstance(defn.type, FunctionLike)
 
-    mangled_name = f"_{info.name.lstrip('_')}{_INTERNAL_POST_INIT_SYM_NAME}"
+    mangled_name = _mangle_internal_sym_name(info.fullname, _INTERNAL_POST_INIT_SYM_NAME)
     ideal_sig_method = info.get_method(mangled_name)
     assert ideal_sig_method is not None and ideal_sig_method.type is not None
     ideal_sig = ideal_sig_method.type

test-data/unit/check-dataclasses.test

@@ -226,6 +226,25 @@ reveal_type(d.foo)  # N: Revealed type is "builtins.str"
 reveal_type(d.bar)  # N: Revealed type is "builtins.int"
 [builtins fixtures/dataclasses.pyi]
 
+[case testDataclassCompatibleOverrideEqualName]
+from dataclasses import dataclass, InitVar
+import m
+
+@dataclass
+class D(m.D):
+    x: InitVar[int]
+
+[file m.py]
+from dataclasses import dataclass
+
+@dataclass
+class D:
+    y: int
+
+[out]
+
+[builtins fixtures/dataclasses.pyi]
+
 [case testDataclassIncompatibleFrozenOverride]
 from dataclasses import dataclass
 

test-data/unit/deps.test

@@ -1389,16 +1389,16 @@ class B(A):
 
 [out]
 <m.A.(abstract)> -> <m.B.__init__>, m
-<m.A._A__mypy-replace> -> <m.B._A__mypy-replace>, m
-<m.A._B__mypy-replace> -> m.B._B__mypy-replace
+<m.A._A__m__mypy-replace> -> <m.B._A__m__mypy-replace>, m
+<m.A._B__m__mypy-replace> -> m.B._B__m__mypy-replace
 <m.A.__dataclass_fields__> -> <m.B.__dataclass_fields__>
 <m.A.__init__> -> <m.B.__init__>, m.B.__init__
 <m.A.__new__> -> <m.B.__new__>
 <m.A.x> -> <m.B.x>
 <m.A.y> -> <m.B.y>
 <m.A> -> m, m.A, m.B
 <m.A[wildcard]> -> m
-<m.B._B__mypy-replace> -> m
+<m.B._B__m__mypy-replace> -> m
 <m.B.y> -> m
 <m.B> -> m.B
 <m.Z> -> m
@@ -1422,8 +1422,8 @@ class B(A):
 
 [out]
 <m.A.(abstract)> -> <m.B.__init__>, m
-<m.A._A__mypy-replace> -> <m.B._A__mypy-replace>, m
-<m.A._B__mypy-replace> -> m.B._B__mypy-replace
+<m.A._A__m__mypy-replace> -> <m.B._A__m__mypy-replace>, m
+<m.A._B__m__mypy-replace> -> m.B._B__m__mypy-replace
 <m.A.__dataclass_fields__> -> <m.B.__dataclass_fields__>
 <m.A.__init__> -> <m.B.__init__>, m.B.__init__
 <m.A.__match_args__> -> <m.B.__match_args__>
@@ -1432,7 +1432,7 @@ class B(A):
 <m.A.y> -> <m.B.y>
 <m.A> -> m, m.A, m.B
 <m.A[wildcard]> -> m
-<m.B._B__mypy-replace> -> m
+<m.B._B__m__mypy-replace> -> m
 <m.B.y> -> m
 <m.B> -> m.B
 <m.Z> -> m