#15847: allow args to be a tuple in parse_args

This fixes a regression introduced by the fix for issue #13922.  Although args
is not documented as being allowed to be a tuple, previously this worked and
so naturally there are programs in the field that depend on it.

Patch by Zbyszek Jędrzejewski-Szmek.

diff --git a/Lib/argparse.py b/Lib/argparse.py
index f77c0c2d75f942499883d160ace96e0e8f2c3201..52ed3ab107aa9313fada45eac218e1ed47fe24ef 100644 (file)
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1701,9 +1701,12 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         return args
 
     def parse_known_args(self, args=None, namespace=None):
-        # args default to the system args
         if args is None:
+            # args default to the system args
             args = _sys.argv[1:]
+        else:
+            # make sure that args are mutable
+            args = list(args)
 
         # default Namespace built from parser defaults
         if namespace is None:

diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index cc051607e974d343448180e2ee24c9e62734c03c..a2f9a69a59a8d838a44c3d117c689aba815fcb72 100644 (file)
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -4522,6 +4522,24 @@ class TestTypeFunctionCallWithNonStringDefault(TestCase):
 
 class TestParseKnownArgs(TestCase):
 
+    def test_arguments_tuple(self):
+        parser = argparse.ArgumentParser()
+        parser.parse_args(())
+
+    def test_arguments_list(self):
+        parser = argparse.ArgumentParser()
+        parser.parse_args([])
+
+    def test_arguments_tuple_positional(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('x')
+        parser.parse_args(('x',))
+
+    def test_arguments_list_positional(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('x')
+        parser.parse_args(['x'])
+
     def test_optionals(self):
         parser = argparse.ArgumentParser()
         parser.add_argument('--foo')