Signature inference for attributes inherited from generic dataclasses

AUTHORS.txt

@@ -62,6 +62,7 @@ Code Contributors
 - Andrii Kolomoiets (@muffinmad)
 - Leo Ryu (@Leo-Ryu)
 - Joseph Birkner (@josephbirkner)
+- Brent Yi (@brentyi)
 
 And a few more "anonymous" contributors.
 

jedi/plugins/stdlib.py

@@ -603,7 +603,18 @@ class DataclassWrapper(ValueWrapper, ClassMixin):
     def get_signatures(self):
         param_names = []
         for cls in reversed(list(self.py__mro__())):
-            if isinstance(cls, DataclassWrapper):
+
+            # Handle cases where DataclassWrapper objects are nested inside of
+            # Decoratee, GenericClass, etc -- these are all subclasses of ValueWrapper
+            # or LazyValueWrapper.
+            is_dataclass = False
+            while isinstance(cls, (ValueWrapper, LazyValueWrapper)):
+                if isinstance(cls, DataclassWrapper):
+                    is_dataclass = True
+                    break
+                cls = cls._wrapped_value
+
+            if is_dataclass:
                 filter_ = cls.as_context().get_global_filter()
                 # .values ordering is not guaranteed, at least not in
                 # Python < 3.6, when dicts where not ordered, which is an

test/test_inference/test_signature.py

@@ -315,6 +315,26 @@ class Y():
              z = 5
          @dataclass
          class X(Y):'''), ['y']],
+        [dedent('''
+         from typing import Generic, TypeVar
+         T = TypeVar("T")
+         @dataclass
+         class Y(Generic[T]):
+             y: T
+             z = 5
+         @dataclass
+         class X(Y[int]):'''), ['y']],
+        [dedent('''
+         from typing import Generic, TypeVar
+         T = TypeVar("T")
+         @dataclass
+         class Z:
+             z: int
+         @dataclass
+         class Y(Z, Generic[T]):
+             y: T
+         @dataclass
+         class X(Y[int]):'''), ['z', 'y']],
     ]
 )
 def test_dataclass_signature(Script, skip_pre_python37, start, start_params):