Add regression test for #5771 (#5908)

ChangeLog

@@ -154,6 +154,12 @@ Release date: TBA
   Closes #5408
   Ref PyCQA/astroid#1392
 
+* Fixed false positive for ``unused-argument`` when a method overridden in a subclass
+  does nothing with the value of a keyword-only argument.
+
+  Closes #5771
+  Ref PyCQA/astroid#1382
+
 * The issue template for crashes is now created for crashes which were previously not covered
   by this mechanism.
 

doc/whatsnew/2.13.rst

@@ -247,6 +247,12 @@ Other Changes
   Closes #5408
   Ref PyCQA/astroid#1392
 
+* Fixed false positive for ``unused-argument`` when a method overridden in a subclass
+  does nothing with the value of a keyword-only argument.
+
+  Closes #5771
+  Ref PyCQA/astroid#1382
+
 * Fix ``unnecessary_dict_index_lookup`` false positive when deleting a dictionary's entry.
 
   Closes #4716

pylint/checkers/variables.py

@@ -2310,9 +2310,7 @@ def _check_is_unused(self, name, node, stmt, global_names, nonlocal_names):
             if global_names and _import_name_is_global(stmt, global_names):
                 return
 
-        argnames = list(
-            itertools.chain(node.argnames(), [arg.name for arg in node.args.kwonlyargs])
-        )
+        argnames = node.argnames()
         # Care about functions with unknown argument (builtins)
         if name in argnames:
             self._check_unused_arguments(name, node, stmt, argnames)

tests/functional/u/unused/unused_argument.py

@@ -87,3 +87,18 @@ class BBBB(object):
     def __init__(self, arg):  # [unused-argument]
         """Constructor with an extra parameter. Should raise a warning"""
         self.spam = 1
+
+
+# Regression test for https://github.com/PyCQA/pylint/issues/5771
+# involving keyword-only arguments
+class Ancestor:
+    def __init__(self):
+        self.thing = None
+
+    def set_thing(self, thing, *, other=None):  # [unused-argument]
+        self.thing = thing
+
+class Descendant(Ancestor):
+    def set_thing(self, thing, *, other=None):
+        """Subclass does not raise unused-argument"""
+        self.thing = thing

tests/functional/u/unused/unused_argument.txt

@@ -6,3 +6,4 @@ unused-argument:61:21:61:24:AAAA.method:Unused argument 'arg':INFERENCE
 unused-argument:68:0:None:None:AAAA.selected:Unused argument 'args':INFERENCE
 unused-argument:68:0:None:None:AAAA.selected:Unused argument 'kwargs':INFERENCE
 unused-argument:87:23:87:26:BBBB.__init__:Unused argument 'arg':INFERENCE
+unused-argument:98:34:98:39:Ancestor.set_thing:Unused argument 'other':INFERENCE