gh-110131: Drop the test, show a non-empty default in the example

Author: v0ropaev

Doc/library/argparse.rst

@@ -827,6 +827,11 @@ how the command-line arguments should be handled. The supplied actions are:
     >>> parser.add_argument("--foo", action="extend", nargs="+", type=str)
     >>> parser.parse_args(["--foo", "f1", "--foo", "f2", "f3", "f4"])
     Namespace(foo=['f1', 'f2', 'f3', 'f4'])
+    >>> parser = argparse.ArgumentParser()
+    >>> parser.add_argument("--foo", action="extend", nargs="+", type=str,
+    ...                     default=["d1"])
+    >>> parser.parse_args(["--foo", "f1", "f2"])
+    Namespace(foo=['d1', 'f1', 'f2'])
 
   .. versionadded:: 3.8
 

Lib/test/test_argparse.py

@@ -2470,21 +2470,6 @@ class TestActionExtend(ParserTestCase):
     ]
 
 
-class TestActionExtendWithDefault(ParserTestCase):
-    """Tests the extend action for an Optional with a non-empty default"""
-
-    argument_signatures = [
-        Sig('--baz', action='extend', nargs='+', default=['X']),
-    ]
-    failures = ['a', '--baz', 'a --baz']
-    successes = [
-        ('', NS(baz=['X'])),
-        ('--baz a', NS(baz=['X', 'a'])),
-        ('--baz a b', NS(baz=['X', 'a', 'b'])),
-        ('--baz a --baz b c', NS(baz=['X', 'a', 'b', 'c'])),
-    ]
-
-
 class TestNegativeNumber(ParserTestCase):
     """Test parsing negative numbers"""