Fix crash while iteraring over a class attribute (#7386)

Co-authored-by: orSolocate <38433858+orSolocate@users.noreply.github.com>

doc/whatsnew/fragments/7380.bugfix

@@ -0,0 +1,3 @@
+Update ``modified_iterating`` checker to fix a crash with ``for`` loops on empty list.
+
+Closes #7380

pylint/checkers/modified_iterating_checker.py

@@ -81,7 +81,7 @@ def _modified_iterating_check(
                 msg_id = "modified-iterating-dict"
             elif isinstance(inferred, nodes.Set):
                 msg_id = "modified-iterating-set"
-        elif not isinstance(iter_obj, nodes.Name):
+        elif not isinstance(iter_obj, (nodes.Name, nodes.Attribute)):
             pass
         elif self._modified_iterating_list_cond(node, iter_obj):
             msg_id = "modified-iterating-list"
@@ -90,10 +90,14 @@ def _modified_iterating_check(
         elif self._modified_iterating_set_cond(node, iter_obj):
             msg_id = "modified-iterating-set"
         if msg_id:
+            if isinstance(iter_obj, nodes.Attribute):
+                obj_name = iter_obj.attrname
+            else:
+                obj_name = iter_obj.name
             self.add_message(
                 msg_id,
                 node=node,
-                args=(iter_obj.name,),
+                args=(obj_name,),
                 confidence=interfaces.INFERENCE,
             )
 

tests/functional/m/modified_iterating.py

@@ -1,5 +1,5 @@
 """Tests for iterating-modified messages"""
-# pylint: disable=not-callable,unnecessary-comprehension
+# pylint: disable=not-callable,unnecessary-comprehension,too-few-public-methods
 
 import copy
 
@@ -26,7 +26,7 @@
 i = 1
 for item in my_dict:
     item_list[0] = i  # for coverage, see reference at /pull/5628#discussion_r792181642
-    my_dict[i] = 1      # [modified-iterating-dict]
+    my_dict[i] = 1  # [modified-iterating-dict]
     i += 1
 
 i = 1
@@ -93,3 +93,15 @@ def update_existing_key():
     for key in my_dict:
         new_key = key.lower()
         my_dict[new_key] = 1  # [modified-iterating-dict]
+
+
+class MyClass:
+    """Regression test for https://github.com/PyCQA/pylint/issues/7380"""
+
+    def __init__(self) -> None:
+        self.attribute = [1, 2, 3]
+
+    def my_method(self):
+        """This should raise as we are deleting."""
+        for var in self.attribute:
+            del var  # [modified-iterating-list]

tests/functional/m/modified_iterating.txt

@@ -13,3 +13,4 @@ modified-iterating-list:64:4:64:23::Iterated list 'item_list' is being modified
 modified-iterating-list:67:12:67:31::Iterated list 'item_list' is being modified inside for loop body, consider iterating through a copy of it instead.:INFERENCE
 modified-iterating-list:69:16:69:35::Iterated list 'item_list' is being modified inside for loop body, consider iterating through a copy of it instead.:INFERENCE
 modified-iterating-dict:95:8:95:28:update_existing_key:Iterated dict 'my_dict' is being modified inside for loop body, iterate through a copy of it instead.:INFERENCE
+modified-iterating-list:107:12:107:19:MyClass.my_method:Iterated list 'attribute' is being modified inside for loop body, consider iterating through a copy of it instead.:INFERENCE