Added support for argparse sub-commands when using cmd2 decorators

Modified the do_help() method to behave differently for methods which have been decorated with an argparse ArgumentParser.
This is so that help will properly deal with sub-command help.

Suppose you have a base command "base" which has two sub-commands, "foo" and "bar".  Then "help base" will provide very different help text than "help base foo".

Slightly tweaked the two argparse decorators to set an attribute in the decorated function's dictionary so that the do_help method can know which functions have an ArgumentParser and which do not.

Added a "subcommands.py" example for demonstrating how to create and use subcommands based on argparse and the cmd2 @with_argument_parser decorator.

Author: tleonhardt

cmd2.py

@@ -292,7 +292,12 @@ def cmd_wrapper(instance, cmdline):
             argparser.description = func.__doc__
 
         cmd_wrapper.__doc__ = argparser.format_help()
+
+        # Mark this function as having an argparse ArgumentParser (used by do_help)
+        cmd_wrapper.__dict__['has_parser'] = True
+
         return cmd_wrapper
+
     return arg_decorator
 
 
@@ -316,7 +321,12 @@ def cmd_wrapper(instance, cmdline):
             argparser.description = func.__doc__
 
         cmd_wrapper.__doc__ = argparser.format_help()
+
+        # Mark this function as having an argparse ArgumentParser (used by do_help)
+        cmd_wrapper.__dict__['has_parser'] = True
+
         return cmd_wrapper
+
     return arg_decorator
 
 
@@ -1198,8 +1208,16 @@ def do_help(self, arglist):
             # Getting help for a specific command
             funcname = self._func_named(arglist[0])
             if funcname:
-                # No special behavior needed, delegate to cmd base class do_help()
-                cmd.Cmd.do_help(self, funcname[3:])
+                # Check to see if this function was decorated with an argparse ArgumentParser
+                func = getattr(self, funcname)
+                if func.__dict__.get('has_parser', False):
+                    # Function has an argparser, so get help based on all the arguments in case there are sub-commands
+                    new_arglist = arglist[1:]
+                    new_arglist.append('-h')
+                    func(new_arglist)
+                else:
+                    # No special behavior needed, delegate to cmd base class do_help()
+                    cmd.Cmd.do_help(self, funcname[3:])
         else:
             # Show a menu of what commands help can be gotten for
             self._help_menu()

examples/subcommands.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python
+# coding=utf-8
+"""A simple example demonstrating how to use Argparse to support sub-commands.
+
+
+This example shows an easy way for a single command to have many subcommands, each of which takes different arguments
+and provides separate contextual help.
+"""
+import argparse
+
+import cmd2
+from cmd2 import with_argument_parser
+
+
+class SubcommandsExample(cmd2.Cmd):
+    """ Example cmd2 application where we a base command which has a couple subcommands."""
+
+    def __init__(self):
+        cmd2.Cmd.__init__(self)
+
+    # sub-command functions for the base command
+    def foo(self, args):
+        """foo subcommand of base command"""
+        print(args.x * args.y)
+
+    def bar(self, args):
+        """bar sucommand of base command"""
+        print('((%s))' % args.z)
+
+    # create the top-level parser
+    base_parser = argparse.ArgumentParser(prog='base')
+    base_subparsers = base_parser.add_subparsers(title='subcommands', help='subcommand help')
+
+    # create the parser for the "foo" command
+    parser_foo = base_subparsers.add_parser('foo', help='foo help')
+    parser_foo.add_argument('-x', type=int, default=1, help='integer')
+    parser_foo.add_argument('y', type=float, help='float')
+    parser_foo.set_defaults(func=foo)
+
+    # create the parser for the "bar" command
+    parser_bar = base_subparsers.add_parser('bar', help='bar help')
+    parser_bar.add_argument('z', help='string')
+    parser_bar.set_defaults(func=bar)
+
+    @with_argument_parser(base_parser)
+    def do_base(self, args):
+        """Base command help"""
+        try:
+            # Call whatever sub-command function was selected
+            args.func(self, args)
+        except AttributeError:
+            # No sub-command was provided, so as called
+            self.do_help('base')
+
+
+if __name__ == '__main__':
+    app = SubcommandsExample()
+    app.cmdloop()