argparse brain: avoid spurious addition of "namespace" to function …

…locals

ChangeLog

@@ -16,6 +16,10 @@ Release date: TBA
 * The Qt brain now correctly treats calling ``.disconnect()`` (with no
   arguments) on a slot as valid.
 
+* The argparse brain no longer incorrectly adds ``"Namespace"`` to the locals
+  of functions that return an ``argparse.Namespace`` object.
+
+  Refs PyCQA/pylint#6895
 
 What's New in astroid 2.11.5?
 =============================

astroid/brain/brain_argparse.py

@@ -13,7 +13,10 @@ def infer_namespace(node, context=None):
         # Cannot make sense of it.
         raise UseInferenceDefault()
 
-    class_node = nodes.ClassDef("Namespace", parent=node.parent)
+    class_node = nodes.ClassDef("Namespace")
+    # Set parent manually until ClassDef constructor fixed:
+    # https://github.com/PyCQA/astroid/issues/1490
+    class_node.parent = node.parent
     for attr in set(callsite.keyword_arguments):
         fake_node = nodes.EmptyNode()
         fake_node.parent = class_node

tests/unittest_brain_argparse.py

@@ -0,0 +1,21 @@
+# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
+# For details: https://github.com/PyCQA/astroid/blob/main/LICENSE
+# Copyright (c) https://github.com/PyCQA/astroid/blob/main/CONTRIBUTORS.txt
+
+from astroid import bases, extract_node, nodes
+
+
+class TestBrainArgparse:
+    @staticmethod
+    def test_infer_namespace() -> None:
+        func = extract_node(
+            """
+        import argparse
+        def make_namespace():  #@
+            return argparse.Namespace(debug=True)
+        """
+        )
+        assert isinstance(func, nodes.FunctionDef)
+        inferred = next(func.infer_call_result(func))
+        assert isinstance(inferred, bases.Instance)
+        assert not func.locals