Fix false positive ``unused-private-member`` for accessing attributes in a class using ``cls`` (#4965)

* Fix false positive ``unused-private-member`` for accessing attributes in
a class using ``cls``

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

5 files changed, 39 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index d3f05dba1..9a46cdfc9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -63,6 +63,10 @@ Release date: TBA
 
   Closes #4907
 
+* Fix false positive ``unused-private-member`` for accessing attributes in a class using ``cls``
+
+  Closes #4849
+
 * Fix false positive ``unused-private-member`` for private staticmethods accessed in classmethods.
 
   Closes #4849
diff --git a/doc/whatsnew/2.11.rst b/doc/whatsnew/2.11.rst
index 0a239025f..f04020796 100644
--- a/doc/whatsnew/2.11.rst
+++ b/doc/whatsnew/2.11.rst
@@ -70,6 +70,10 @@ Other Changes
 
   Closes #4907
 
+* Fix false positive ``unused-private-member`` for accessing attributes in a class using ``cls``
+
+  Closes #4849
+
 * Extended ``consider-using-in`` check to work for attribute access.
 
 * Setting ``min-similarity-lines`` to 0 now makes the similarty checker stop checking for duplicate code
diff --git a/pylint/checkers/classes.py b/pylint/checkers/classes.py
index 3ce95033e..4e208f064 100644
--- a/pylint/checkers/classes.py
+++ b/pylint/checkers/classes.py
@@ -1003,11 +1003,15 @@ a metaclass class method.",
                 if attribute.attrname != assign_attr.attrname:
                     continue
 
-                if assign_attr.expr.name == "cls" and attribute.expr.name in [
-                    "cls",
-                    "self",
-                ]:
-                    # If assigned to cls.attrib, can be accessed by cls/self
+                if (
+                    assign_attr.expr.name
+                    in [
+                        "cls",
+                        node.name,
+                    ]
+                    and attribute.expr.name in ["cls", "self", node.name]
+                ):
+                    # If assigned to cls or class name, can be accessed by cls/self/class name
                     break
 
                 if (
diff --git a/tests/functional/u/unused/unused_private_member.py b/tests/functional/u/unused/unused_private_member.py
index 9c3d37303..319a06d88 100644
--- a/tests/functional/u/unused/unused_private_member.py
+++ b/tests/functional/u/unused/unused_private_member.py
@@ -242,6 +242,25 @@ class FalsePositive4681:
             FalsePositive4681.__instance = False  # This should be fine
             FalsePositive4681.__should_cause_error = False  # [unused-private-member]
 
+# Accessing attributes of the class using `cls` should not result in a false positive
+# as long as it is used within the class
+class FalsePositive4681b:
+    __instance = None
+
+    @classmethod  # Use class method here
+    def instance(cls):
+        if cls.__instance is None:
+            cls()
+        return cls.__instance
+
+    def __init__(self):
+        try:
+            FalsePositive4681b.__instance = 42  # This should be fine
+        except Exception:  # pylint: disable=broad-except
+            print("Error")
+            FalsePositive4681b.__instance = False  # This should be fine
+
+
 # https://github.com/PyCQA/pylint/issues/4849
 # Accessing private static methods from classmethods via `cls` should not result in a
 # false positive
diff --git a/tests/functional/u/unused/unused_private_member.txt b/tests/functional/u/unused/unused_private_member.txt
index 1d5baa9dc..08adc8c15 100644
--- a/tests/functional/u/unused/unused_private_member.txt
+++ b/tests/functional/u/unused/unused_private_member.txt
@@ -14,6 +14,6 @@ unused-private-member:212:8:Crash4755Context.__init__:Unused private member `Cra
 unused-private-member:229:4:FalsePositive4681:Unused private member `FalsePositive4681.__should_cause_error`:HIGH
 unused-private-member:239:12:FalsePositive4681.__init__:Unused private member `FalsePositive4681.__should_cause_error`:HIGH
 unused-private-member:243:12:FalsePositive4681.__init__:Unused private member `FalsePositive4681.__should_cause_error`:HIGH
-unused-private-member:255:4:FalsePositive4849.__unused_private_method:Unused private member `FalsePositive4849.__unused_private_method()`:HIGH
-unused-private-member:272:4:Pony.__init_defaults:Unused private member `Pony.__init_defaults(self)`:HIGH
-unused-private-member:277:4:Pony.__get_fur_color:Unused private member `Pony.__get_fur_color(self)`:HIGH
+unused-private-member:274:4:FalsePositive4849.__unused_private_method:Unused private member `FalsePositive4849.__unused_private_method()`:HIGH
+unused-private-member:291:4:Pony.__init_defaults:Unused private member `Pony.__init_defaults(self)`:HIGH
+unused-private-member:296:4:Pony.__get_fur_color:Unused private member `Pony.__get_fur_color(self)`:HIGH