Add support for Pydantic models in stubgen

mypy/stubgen.py

@@ -861,13 +861,8 @@ def visit_class_def(self, o: ClassDef) -> None:
         if self.analyzed and (spec := find_dataclass_transform_spec(o)):
             self.processing_dataclass = True
             self.dataclass_field_specifier = spec.field_specifiers
-        for base_type_expr in o.base_type_exprs:
-            if (
-                isinstance(base_type_expr, (NameExpr, MemberExpr))
-                and self.get_fullname(base_type_expr) == "pydantic.BaseModel"
-            ):
-                self.processing_pydantic_model = True
-                break
+        if self._inherits_from_pydantic_basemodel(o):
+            self.processing_pydantic_model = True
         super().visit_class_def(o)
         self.dedent()
         self._vars.pop()
@@ -887,6 +882,20 @@ def visit_class_def(self, o: ClassDef) -> None:
         self.processing_enum = False
         self.processing_pydantic_model = False
 
+    def _inherits_from_pydantic_basemodel(self, class_def: ClassDef) -> bool:
+        """Check if a class directly or indirectly inherits from pydantic.BaseModel"""
+        for base_type_expr in class_def.base_type_exprs:
+            if (
+                isinstance(base_type_expr, (NameExpr, MemberExpr)) 
+                and self.get_fullname(base_type_expr) == "pydantic.BaseModel"
+            ):
+                return True
+        if self.analyzed and class_def.info:
+            for base_class in class_def.info.mro:
+                if base_class.fullname == "pydantic.BaseModel":
+                    return True
+        return False
+
     def get_base_types(self, cdef: ClassDef) -> list[str]:
         """Get list of base classes for a class."""
         base_types: list[str] = []

test-data/unit/stubgen.test

@@ -4801,7 +4801,7 @@ class User(BaseModel):
     age: int
     address: Address | None = ...
 
-[case testPydanticBaseModelInheritance]
+[case testPydanticBaseModelInheritance_semanal]
 from pydantic import BaseModel
 
 class BaseUser(BaseModel):