unnecessary-ellipsis false positive: allow ellipsis as default argu…

…ment (#6007)

ChangeLog

@@ -20,6 +20,10 @@ What's New in Pylint 2.13.3?
 ============================
 Release date: TBA
 
+* Fix false positive for ``unnecessary-ellipsis`` when using an ellipsis as a default argument.
+
+  Closes #5973
+
 * Fix crash involving unbalanced tuple unpacking.
 
   Closes #5998

doc/whatsnew/2.13.rst

@@ -128,6 +128,10 @@ Extensions
 Other Changes
 =============
 
+* Fix false positive for ``unnecessary-ellipsis`` when using an ellipsis as a default argument.
+
+  Closes #5973
+
 * Add missing dunder methods to ``unexpected-special-method-signature`` check.
 
 * No longer emit ``no-member`` in for loops that reference ``self`` if the binary operation that

pylint/checkers/ellipsis_checker.py

@@ -41,7 +41,10 @@ def visit_const(self, node: nodes.Const) -> None:
         """
         if (
             node.pytype() == "builtins.Ellipsis"
-            and not isinstance(node.parent, (nodes.Assign, nodes.AnnAssign, nodes.Call))
+            and not isinstance(
+                node.parent,
+                (nodes.Assign, nodes.AnnAssign, nodes.Call, nodes.Arguments),
+            )
             and (
                 len(node.parent.parent.child_sequence(node.parent)) > 1
                 or (

tests/functional/u/unnecessary/unnecessary_ellipsis.py

@@ -1,6 +1,6 @@
 """Emit a warning when the ellipsis constant is used and can be avoided"""
 
-# pylint: disable=missing-docstring, too-few-public-methods
+# pylint: disable=missing-docstring, too-few-public-methods, invalid-name, unused-argument
 
 from typing import List, overload, Union
 
@@ -97,3 +97,7 @@ def __getitem__(self, index: Union[int, slice]) -> Union[int, List[int]]:
             ...
         else:
             raise TypeError(...)
+
+# Ellipsis is allowed as a default argument
+def func_with_ellipsis_default_arg(a = ...) -> None:
+    "Some docstring."