Fixed 'index out of range' error when passing no arguments to an argparse-based command function.

Author: kmvanbrunt

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.5.9 (TBD)
+* Bug Fixes
+   * Fixed 'index out of range' error when passing no arguments to an argparse-based command function.
+
 ## 2.5.8 (December 17, 2024)
 * Bug Fixes
    * Rolled back undocumented changes to printing functions introduced in 2.5.0.

cmd2/decorators.py

@@ -91,7 +91,7 @@ def _parse_positionals(args: Tuple[Any, ...]) -> Tuple['cmd2.Cmd', Union[Stateme
             Cmd,
         )
 
-        if (isinstance(arg, Cmd) or isinstance(arg, CommandSet)) and len(args) > pos:
+        if isinstance(arg, (Cmd, CommandSet)) and len(args) > pos + 1:
             if isinstance(arg, CommandSet):
                 arg = arg._cmd
             next_arg = args[pos + 1]
@@ -100,7 +100,7 @@ def _parse_positionals(args: Tuple[Any, ...]) -> Tuple['cmd2.Cmd', Union[Stateme
 
     # This shouldn't happen unless we forget to pass statement in `Cmd.onecmd` or
     # somehow call the unbound class method.
-    raise TypeError('Expected arguments: cmd: cmd2.Cmd, statement: Union[Statement, str] Not found')  # pragma: no cover
+    raise TypeError('Expected arguments: cmd: cmd2.Cmd, statement: Union[Statement, str] Not found')
 
 
 def _arg_swap(args: Union[Sequence[Any]], search_arg: Any, *replace_arg: Any) -> List[Any]:

tests/test_argparse.py

@@ -148,6 +148,13 @@ def test_argparse_remove_quotes(argparse_app):
     assert out == ['hello there']
 
 
+def test_argparse_with_no_args(argparse_app):
+    """Make sure we receive TypeError when calling argparse-based function with no args"""
+    with pytest.raises(TypeError) as excinfo:
+        argparse_app.do_say()
+    assert 'Expected arguments' in str(excinfo.value)
+
+
 def test_argparser_kwargs(argparse_app, capsys):
     """Test with_argparser wrapper passes through kwargs to command function"""
     argparse_app.do_say('word', keyword_arg="foo")