Added add_existing_parser() method to argparse._SubParsersAction.

Author: kmvanbrunt

cmd2/argparse_custom.py

@@ -231,6 +231,10 @@ def get_choices(self) -> Choices:
 sub-parser from a sub-parsers group. See _SubParsersAction_remove_parser for
 more details.
 
+``argparse._SubParsersAction.add_existing_parser`` - new function which allows you to attach
+an existing ArgumentParser to a sub-parsers group. See _SubParsersAction_add_existing_parser
+for more details.
+
 **Added accessor methods**
 
 cmd2 has patched ``argparse.Action`` to include the following accessor methods
@@ -948,7 +952,10 @@ def _ArgumentParser_check_value(_self: argparse.ArgumentParser, action: argparse
 ############################################################################################################
 
 
-def _SubParsersAction_remove_parser(self: argparse._SubParsersAction, name: str) -> None:  # type: ignore[type-arg]  # noqa: N802
+def _SubParsersAction_remove_parser(  # noqa: N802
+    self: argparse._SubParsersAction,  # type: ignore[type-arg]
+    name: str,
+) -> None:
     """Remove a sub-parser from a sub-parsers group. Used to remove subcommands from a parser.
 
     This function is added by cmd2 as a method called ``remove_parser()`` to ``argparse._SubParsersAction`` class.
@@ -977,6 +984,42 @@ def _SubParsersAction_remove_parser(self: argparse._SubParsersAction, name: str)
 
 setattr(argparse._SubParsersAction, 'remove_parser', _SubParsersAction_remove_parser)
 
+############################################################################################################
+# Patch argparse._SubParsersAction to add add_existing_parser function
+############################################################################################################
+
+
+def _SubParsersAction_add_existing_parser(  # noqa: N802
+    self: argparse._SubParsersAction,  # type: ignore[type-arg]
+    name: str,
+    subcmd_parser: argparse.ArgumentParser,
+    **add_parser_kwargs: Any,
+) -> None:
+    """Attach an existing ArgumentParser to a sub-parsers group.
+
+    This is useful when a parser is pre-configured (e.g. by cmd2's subcommand decorator)
+    and needs to be attached to a parent parser.
+
+    This function is added by cmd2 as a method called ``add_existing_parser()``
+    to ``argparse._SubParsersAction`` class.
+
+    :param self: instance of the _SubParsersAction being edited
+    :param name: name of the subcommand to add
+    :param subcmd_parser: the parser for this new subcommand
+    :param add_parser_kwargs: registration-specific kwargs for add_parser() (e.g. help, aliases, deprecated)
+    """
+    # Use add_parser to register the subcommand name and any aliases
+    self.add_parser(name, **add_parser_kwargs)
+
+    # Replace the parser created by add_parser() with our pre-configured one
+    self._name_parser_map[name] = subcmd_parser
+
+    # Remap any aliases to our pre-configured parser
+    for alias in add_parser_kwargs.get("aliases", []):
+        self._name_parser_map[alias] = subcmd_parser
+
+
+setattr(argparse._SubParsersAction, 'add_existing_parser', _SubParsersAction_add_existing_parser)
 
 ############################################################################################################
 # Unless otherwise noted, everything below this point are copied from Python's

cmd2/cmd2.py

@@ -1129,19 +1129,15 @@ def find_subcommand(
             # Find the argparse action that handles subcommands
             for action in target_parser._actions:
                 if isinstance(action, argparse._SubParsersAction):
-                    # Get the kwargs for add_parser()
+                    # Get add_parser() kwargs (aliases, help, etc.) defined by the decorator
                     add_parser_kwargs = getattr(method, constants.SUBCMD_ATTR_ADD_PARSER_KWARGS, {})
 
-                    # Use add_parser to register the subcommand name and any aliases
-                    action.add_parser(subcommand_name, **add_parser_kwargs)
-
-                    # Replace the parser created by add_parser() with our pre-configured one
-                    action._name_parser_map[subcommand_name] = subcmd_parser
-
-                    # Also remap any aliases to our pre-configured parser
-                    for alias in add_parser_kwargs.get("aliases", []):
-                        action._name_parser_map[alias] = subcmd_parser
-
+                    # Add the existing parser as a subcommand
+                    action.add_existing_parser(  # type: ignore[attr-defined]
+                        subcommand_name,
+                        subcmd_parser,
+                        **add_parser_kwargs,
+                    )
                     break
 
     def _unregister_subcommands(self, cmdset: Union[CommandSet, 'Cmd']) -> None:

cmd2/decorators.py

@@ -353,6 +353,7 @@ def as_subcommand_to(
     *,
     help: str | None = None,  # noqa: A002
     aliases: Sequence[str] | None = None,
+    **add_parser_kwargs: Any,
 ) -> Callable[[ArgparseCommandFunc[CmdOrSet]], ArgparseCommandFunc[CmdOrSet]]:
     """Tag this method as a subcommand to an existing argparse decorated command.
 
@@ -363,6 +364,7 @@ def as_subcommand_to(
                  This is passed as the help argument to subparsers.add_parser().
     :param aliases: Alternative names for this subcommand. This is passed as the alias argument to
                     subparsers.add_parser().
+    :param add_parser_kwargs: other registration-specific kwargs for add_parser() (e.g. deprecated)
     :return: Wrapper function that can receive an argparse.Namespace
     """
 
@@ -373,13 +375,13 @@ def arg_decorator(func: ArgparseCommandFunc[CmdOrSet]) -> ArgparseCommandFunc[Cm
         setattr(func, constants.SUBCMD_ATTR_NAME, subcommand)
 
         # Keyword arguments for subparsers.add_parser()
-        add_parser_kwargs: dict[str, Any] = {}
+        final_kwargs: dict[str, Any] = dict(add_parser_kwargs)
         if help is not None:
-            add_parser_kwargs['help'] = help
+            final_kwargs['help'] = help
         if aliases:
-            add_parser_kwargs['aliases'] = aliases[:]
+            final_kwargs['aliases'] = tuple(aliases)
 
-        setattr(func, constants.SUBCMD_ATTR_ADD_PARSER_KWARGS, add_parser_kwargs)
+        setattr(func, constants.SUBCMD_ATTR_ADD_PARSER_KWARGS, final_kwargs)
 
         return func