django dunder str codemod can detect if parent class has a dunder str

src/codemodder/codemods/utils_mixin.py

@@ -281,6 +281,16 @@ def find_accesses(self, node) -> Collection[Access]:
             return scope.accesses[node]
         return {}
 
+    def class_has_method(self, classdef: cst.ClassDef, method_name: str) -> bool:
+        """Check if a given class definition implements a method of name `method_name`."""
+        for node in classdef.body.body:
+            match node:
+                case cst.FunctionDef(
+                    name=cst.Name(value=value)
+                ) if value == method_name:
+                    return True
+        return False
+
 
 class AncestorPatternsMixin(MetadataDependent):
     METADATA_DEPENDENCIES: ClassVar[Collection[ProviderT]] = (ParentNodeProvider,)

src/core_codemods/django_model_without_dunder_str.py

@@ -43,9 +43,14 @@ def leave_ClassDef(
         return updated_node.with_changes(body=new_body)
 
     def implements_dunder_str(self, original_node: cst.ClassDef) -> bool:
-        for node in original_node.body.body:
-            match node:
-                case cst.FunctionDef(name=cst.Name(value="__str__")):
+        """Check if a ClassDef or its bases implement `__str__`"""
+        if self.class_has_method(original_node, "__str__"):
+            return True
+
+        for base in original_node.bases:
+            if maybe_assignment := self.find_single_assignment(base.value):
+                classdef = maybe_assignment.node
+                if self.class_has_method(classdef, "__str__"):
                     return True
         return False
 

tests/codemods/test_django_model_without_dunder_str.py

@@ -57,51 +57,19 @@ def something():
         """
         self.run_and_assert(tmpdir, input_code, expected)
 
-    # def test_simple_alias(self, tmpdir):
-    #     input_code = """
-    #     from django.dispatch import receiver as rec
-    #
-    #     @csrf_exempt
-    #     @rec(request_finished)
-    #     def foo():
-    #         pass
-    #     """
-    #     expected = """
-    #     from django.dispatch import receiver as rec
-    #
-    #     @rec(request_finished)
-    #     @csrf_exempt
-    #     def foo():
-    #         pass
-    #     """
-    #     self.run_and_assert(tmpdir, input_code, expected)
-    #
-    # def test_no_receiver(self, tmpdir):
-    #     input_code = """
-    #     @csrf_exempt
-    #     def foo():
-    #         pass
-    #     """
-    #     self.run_and_assert(tmpdir, input_code, input_code)
-    #
-    # def test_receiver_but_not_djangos(self, tmpdir):
-    #     input_code = """
-    #     from not_django import receiver
-    #
-    #     @csrf_exempt
-    #     @receiver(request_finished)
-    #     def foo():
-    #         pass
-    #     """
-    #     self.run_and_assert(tmpdir, input_code, input_code)
-    #
-    # def test_receiver_on_top(self, tmpdir):
-    #     input_code = """
-    #     from django.dispatch import receiver
-    #
-    #     @receiver(request_finished)
-    #     @csrf_exempt
-    #     def foo():
-    #         pass
-    #     """
-    #     self.run_and_assert(tmpdir, input_code, input_code)
+    def test_model_inherits_dunder_str(self, tmpdir):
+        input_code = """
+        from django.db import models
+
+        class Custom:
+            def __str__(self):
+                pass
+                        
+        class User(Custom, models.Model):
+            name = models.CharField(max_length=100)
+            phone = models.IntegerField(blank=True)
+
+        def something():
+            pass
+        """
+        self.run_and_assert(tmpdir, input_code, input_code)