All built-in commands now use a function to create their argument parser.

This simplifies the process for overriding cmd2's default parser class.

Author: kmvanbrunt

CHANGELOG.md

@@ -1,8 +1,14 @@
 ## 3.0.0 (TBD)
 
-- Breaking Change
+- Breaking Changes
+
     - Removed macros
 
+- Enhancements
+    - Simplified the process to set a custom parser for `cmd2's` built-in commands. See
+      [custom_parser.py](https://github.com/python-cmd2/cmd2/blob/main/examples/custom_parser.py)
+      example for more details.
+
 ## 2.7.0 (June 30, 2025)
 
 - Enhancements

cmd2/__init__.py

@@ -1,13 +1,12 @@
 """Import certain things for backwards compatibility."""
 
-import argparse
 import contextlib
 import importlib.metadata as importlib_metadata
-import sys
 
 with contextlib.suppress(importlib_metadata.PackageNotFoundError):
     __version__ = importlib_metadata.version(__name__)
 
+from . import plugin
 from .ansi import (
     Bg,
     Cursor,
@@ -19,28 +18,29 @@
     TextStyle,
     style,
 )
+from .argparse_completer import set_default_ap_completer_type
 from .argparse_custom import (
     Cmd2ArgumentParser,
     Cmd2AttributeWrapper,
     CompletionItem,
     register_argparse_argument_parameter,
     set_default_argument_parser_type,
 )
-
-# Check if user has defined a module that sets a custom value for argparse_custom.DEFAULT_ARGUMENT_PARSER.
-# Do this before loading cmd2.Cmd class so its commands use the custom parser.
-cmd2_parser_module = getattr(argparse, 'cmd2_parser_module', None)
-if cmd2_parser_module is not None:
-    import importlib
-
-    importlib.import_module(cmd2_parser_module)
-
-from . import plugin
-from .argparse_completer import set_default_ap_completer_type
 from .cmd2 import Cmd
-from .command_definition import CommandSet, with_default_category
-from .constants import COMMAND_NAME, DEFAULT_SHORTCUTS
-from .decorators import as_subcommand_to, with_argparser, with_argument_list, with_category
+from .command_definition import (
+    CommandSet,
+    with_default_category,
+)
+from .constants import (
+    COMMAND_NAME,
+    DEFAULT_SHORTCUTS,
+)
+from .decorators import (
+    as_subcommand_to,
+    with_argparser,
+    with_argument_list,
+    with_category,
+)
 from .exceptions import (
     Cmd2ArgparseError,
     CommandSetRegistrationError,
@@ -50,7 +50,12 @@
 )
 from .parsing import Statement
 from .py_bridge import CommandResult
-from .utils import CompletionMode, CustomCompletionSettings, Settable, categorize
+from .utils import (
+    CompletionMode,
+    CustomCompletionSettings,
+    Settable,
+    categorize,
+)
 
 __all__: list[str] = [  # noqa: RUF022
     'COMMAND_NAME',
@@ -70,8 +75,8 @@
     'Cmd2AttributeWrapper',
     'CompletionItem',
     'register_argparse_argument_parameter',
-    'set_default_argument_parser_type',
     'set_default_ap_completer_type',
+    'set_default_argument_parser_type',
     # Cmd2
     'Cmd',
     'CommandResult',
@@ -87,6 +92,7 @@
     'Cmd2ArgparseError',
     'CommandSetRegistrationError',
     'CompletionError',
+    'PassThroughException',
     'SkipPostcommandHooks',
     # modules
     'plugin',

cmd2/argparse_custom.py

@@ -1378,15 +1378,20 @@ def set(self, new_val: Any) -> None:
         self.__attribute = new_val
 
 
-# The default ArgumentParser class for a cmd2 app
-DEFAULT_ARGUMENT_PARSER: type[argparse.ArgumentParser] = Cmd2ArgumentParser
+# Parser type used by cmd2's built-in commands.
+# Set it using cmd2.set_default_argument_parser_type().
+DEFAULT_ARGUMENT_PARSER: type[Cmd2ArgumentParser] = Cmd2ArgumentParser
 
 
-def set_default_argument_parser_type(parser_type: type[argparse.ArgumentParser]) -> None:
-    """Set the default ArgumentParser class for a cmd2 app.
+def set_default_argument_parser_type(parser_type: type[Cmd2ArgumentParser]) -> None:
+    """Set the default ArgumentParser class for cmd2's built-in commands.
 
-    This must be called prior to loading cmd2.py if you want to override the parser for cmd2's built-in commands.
-    See examples/override_parser.py.
+    Since built-in commands rely on customizations made in Cmd2ArgumentParser,
+    your custom parser class should inherit from Cmd2ArgumentParser.
+
+    This should be called prior to instantiating your CLI object.
+
+    See examples/custom_parser.py.
     """
     global DEFAULT_ARGUMENT_PARSER  # noqa: PLW0603
     DEFAULT_ARGUMENT_PARSER = parser_type