Fix 'index out of range' error in decorators._parse_positionals(). (#1401)

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

* Added Callable types for argparse-based commands which use with_unknown_args.

* Fixed broken example.

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]:
@@ -118,17 +118,17 @@ def _arg_swap(args: Union[Sequence[Any]], search_arg: Any, *replace_arg: Any) ->
     return args_list
 
 
-#: Function signature for an Command Function that accepts a pre-processed argument list from user input
+#: Function signature for a command function that accepts a pre-processed argument list from user input
 #: and optionally returns a boolean
 ArgListCommandFuncOptionalBoolReturn = Callable[[CommandParent, List[str]], Optional[bool]]
-#: Function signature for an Command Function that accepts a pre-processed argument list from user input
+#: Function signature for a command function that accepts a pre-processed argument list from user input
 #: and returns a boolean
 ArgListCommandFuncBoolReturn = Callable[[CommandParent, List[str]], bool]
-#: Function signature for an Command Function that accepts a pre-processed argument list from user input
+#: Function signature for a command function that accepts a pre-processed argument list from user input
 #: and returns Nothing
 ArgListCommandFuncNoneReturn = Callable[[CommandParent, List[str]], None]
 
-#: Aggregate of all accepted function signatures for Command Functions that accept a pre-processed argument list
+#: Aggregate of all accepted function signatures for command functions that accept a pre-processed argument list
 ArgListCommandFunc = Union[
     ArgListCommandFuncOptionalBoolReturn[CommandParent],
     ArgListCommandFuncBoolReturn[CommandParent],
@@ -249,21 +249,29 @@ def _set_parser_prog(parser: argparse.ArgumentParser, prog: str) -> None:
             req_args.append(action.dest)
 
 
-#: Function signature for a Command Function that uses an argparse.ArgumentParser to process user input
-#: and optionally returns a boolean
+#: Function signatures for command functions that use an argparse.ArgumentParser to process user input
+#: and optionally return a boolean
 ArgparseCommandFuncOptionalBoolReturn = Callable[[CommandParent, argparse.Namespace], Optional[bool]]
-#: Function signature for a Command Function that uses an argparse.ArgumentParser to process user input
-#: and returns a boolean
+ArgparseCommandFuncWithUnknownArgsOptionalBoolReturn = Callable[[CommandParent, argparse.Namespace, List[str]], Optional[bool]]
+
+#: Function signatures for command functions that use an argparse.ArgumentParser to process user input
+#: and return a boolean
 ArgparseCommandFuncBoolReturn = Callable[[CommandParent, argparse.Namespace], bool]
-#: Function signature for an Command Function that uses an argparse.ArgumentParser to process user input
-#: and returns nothing
+ArgparseCommandFuncWithUnknownArgsBoolReturn = Callable[[CommandParent, argparse.Namespace, List[str]], bool]
+
+#: Function signatures for command functions that use an argparse.ArgumentParser to process user input
+#: and return nothing
 ArgparseCommandFuncNoneReturn = Callable[[CommandParent, argparse.Namespace], None]
+ArgparseCommandFuncWithUnknownArgsNoneReturn = Callable[[CommandParent, argparse.Namespace, List[str]], None]
 
-#: Aggregate of all accepted function signatures for an argparse Command Function
+#: Aggregate of all accepted function signatures for an argparse command function
 ArgparseCommandFunc = Union[
     ArgparseCommandFuncOptionalBoolReturn[CommandParent],
+    ArgparseCommandFuncWithUnknownArgsOptionalBoolReturn[CommandParent],
     ArgparseCommandFuncBoolReturn[CommandParent],
+    ArgparseCommandFuncWithUnknownArgsBoolReturn[CommandParent],
     ArgparseCommandFuncNoneReturn[CommandParent],
+    ArgparseCommandFuncWithUnknownArgsNoneReturn[CommandParent],
 ]
 
 

examples/modular_commands/commandset_basic.py

@@ -8,7 +8,6 @@
 )
 
 from cmd2 import (
-    Cmd,
     CommandSet,
     CompletionError,
     Statement,
@@ -32,15 +31,15 @@ class BasicCompletionCommandSet(CommandSet):
         '/home/other user/tests.db',
     ]
 
-    def do_flag_based(self, cmd: Cmd, statement: Statement):
+    def do_flag_based(self, statement: Statement) -> None:
         """Tab completes arguments based on a preceding flag using flag_based_complete
         -f, --food [completes food items]
         -s, --sport [completes sports]
         -p, --path [completes local file system paths]
         """
         self._cmd.poutput("Args: {}".format(statement.args))
 
-    def complete_flag_based(self, cmd: Cmd, text: str, line: str, begidx: int, endidx: int) -> List[str]:
+    def complete_flag_based(self, text: str, line: str, begidx: int, endidx: int) -> List[str]:
         """Completion function for do_flag_based"""
         flag_dict = {
             # Tab complete food items after -f and --food flags in command line
@@ -50,38 +49,38 @@ def complete_flag_based(self, cmd: Cmd, text: str, line: str, begidx: int, endid
             '-s': self.sport_item_strs,
             '--sport': self.sport_item_strs,
             # Tab complete using path_complete function after -p and --path flags in command line
-            '-p': cmd.path_complete,
-            '--path': cmd.path_complete,
+            '-p': self._cmd.path_complete,
+            '--path': self._cmd.path_complete,
         }
 
-        return cmd.flag_based_complete(text, line, begidx, endidx, flag_dict=flag_dict)
+        return self._cmd.flag_based_complete(text, line, begidx, endidx, flag_dict=flag_dict)
 
-    def do_index_based(self, cmd: Cmd, statement: Statement):
+    def do_index_based(self, statement: Statement) -> None:
         """Tab completes first 3 arguments using index_based_complete"""
         self._cmd.poutput("Args: {}".format(statement.args))
 
-    def complete_index_based(self, cmd: Cmd, text: str, line: str, begidx: int, endidx: int) -> List[str]:
+    def complete_index_based(self, text: str, line: str, begidx: int, endidx: int) -> List[str]:
         """Completion function for do_index_based"""
         index_dict = {
             1: self.food_item_strs,  # Tab complete food items at index 1 in command line
             2: self.sport_item_strs,  # Tab complete sport items at index 2 in command line
-            3: cmd.path_complete,  # Tab complete using path_complete function at index 3 in command line
+            3: self._cmd.path_complete,  # Tab complete using path_complete function at index 3 in command line
         }
 
-        return cmd.index_based_complete(text, line, begidx, endidx, index_dict=index_dict)
+        return self._cmd.index_based_complete(text, line, begidx, endidx, index_dict=index_dict)
 
-    def do_delimiter_complete(self, cmd: Cmd, statement: Statement):
+    def do_delimiter_complete(self, statement: Statement) -> None:
         """Tab completes files from a list using delimiter_complete"""
         self._cmd.poutput("Args: {}".format(statement.args))
 
-    def complete_delimiter_complete(self, cmd: Cmd, text: str, line: str, begidx: int, endidx: int) -> List[str]:
-        return cmd.delimiter_complete(text, line, begidx, endidx, match_against=self.file_strs, delimiter='/')
+    def complete_delimiter_complete(self, text: str, line: str, begidx: int, endidx: int) -> List[str]:
+        return self._cmd.delimiter_complete(text, line, begidx, endidx, match_against=self.file_strs, delimiter='/')
 
-    def do_raise_error(self, cmd: Cmd, statement: Statement):
+    def do_raise_error(self, statement: Statement) -> None:
         """Demonstrates effect of raising CompletionError"""
         self._cmd.poutput("Args: {}".format(statement.args))
 
-    def complete_raise_error(self, cmd: Cmd, text: str, line: str, begidx: int, endidx: int) -> List[str]:
+    def complete_raise_error(self, text: str, line: str, begidx: int, endidx: int) -> List[str]:
         """
         CompletionErrors can be raised if an error occurs while tab completing.
 
@@ -92,5 +91,5 @@ def complete_raise_error(self, cmd: Cmd, text: str, line: str, begidx: int, endi
         raise CompletionError("This is how a CompletionError behaves")
 
     @with_category('Not Basic Completion')
-    def do_custom_category(self, cmd: Cmd, statement: Statement):
+    def do_custom_category(self, statement: Statement) -> None:
         self._cmd.poutput('Demonstrates a command that bypasses the default category')

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")