class attrs should not emit assigning-non-slot msg

Author: clavedeluna

doc/whatsnew/fragments/6001.false_positive

@@ -0,0 +1,3 @@
+Fix false positive ``assigning-non-slot`` when a class attribute is re-assigned.
+
+Closes #6001

pylint/checkers/classes/class_checker.py

@@ -1622,7 +1622,6 @@ def _check_in_slots(self, node: nodes.AssignAttr) -> None:
             for ancestor in klass.ancestors()
         ):
             return
-
         if not any(slot.value == node.attrname for slot in slots):
             # If we have a '__dict__' in slots, then
             # assigning any name is valid.
@@ -1631,6 +1630,8 @@ def _check_in_slots(self, node: nodes.AssignAttr) -> None:
                     # Properties circumvent the slots mechanism,
                     # so we should not emit a warning for them.
                     return
+                if self._is_class_attribute(node.attrname, klass):
+                    return
                 if node.attrname in klass.locals:
                     for local_name in klass.locals.get(node.attrname):
                         statement = local_name.statement(future=True)

tests/functional/a/assigning/assigning_non_slot.py

@@ -129,7 +129,7 @@ def dont_emit_for_descriptors():
     # This should not emit, because attr is
     # a data descriptor
     inst.data_descriptor = 'foo'
-    inst.non_data_descriptor = 'lala' # [assigning-non-slot]
+    inst.non_data_descriptor = 'lala'
 
 
 class ClassWithSlots:
@@ -147,7 +147,7 @@ class ClassReassingingInvalidLayoutClass:
     __slots__ = []
 
     def release(self):
-        self.__class__ = ClassWithSlots # [assigning-non-slot]
+        self.__class__ = ClassWithSlots
 
 
 # pylint: disable=attribute-defined-outside-init
@@ -200,3 +200,15 @@ def dont_emit_for_defined_setattr():
 
     child = ClassWithParentDefiningSetattr()
     child.non_existent = "non-existent"
+
+class ColorCls:
+    __slots__ = ()
+    COLOR = "red"
+
+
+class Repro(ColorCls):
+    __slots__ = ()
+
+
+repro = Repro()
+Repro.COLOR = "blue"

tests/functional/a/assigning/assigning_non_slot.txt

@@ -1,5 +1,3 @@
 assigning-non-slot:18:8:18:20:Bad.__init__:Assigning to attribute 'missing' not defined in class slots:UNDEFINED
 assigning-non-slot:26:8:26:20:Bad2.__init__:Assigning to attribute 'missing' not defined in class slots:UNDEFINED
 assigning-non-slot:36:8:36:20:Bad3.__init__:Assigning to attribute 'missing' not defined in class slots:UNDEFINED
-assigning-non-slot:132:4:132:28:dont_emit_for_descriptors:Assigning to attribute 'non_data_descriptor' not defined in class slots:UNDEFINED
-assigning-non-slot:150:8:150:22:ClassReassingingInvalidLayoutClass.release:Assigning to attribute '__class__' not defined in class slots:UNDEFINED