Use add_subparsers() 'required' keyword argument added in Python 3.7.

Author: kmvanbrunt

cmd2/cmd2.py

@@ -3404,8 +3404,7 @@ def _cmdloop(self) -> None:
     alias_description = "Manage aliases\n" "\n" "An alias is a command that enables replacement of a word by another string."
     alias_epilog = "See also:\n" "  macro"
     alias_parser = argparse_custom.DEFAULT_ARGUMENT_PARSER(description=alias_description, epilog=alias_epilog)
-    alias_subparsers = alias_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    alias_subparsers.required = True
+    alias_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     # Preserve quotes since we are passing strings to other commands
     @with_argparser(alias_parser, preserve_quotes=True)
@@ -3573,8 +3572,7 @@ def _alias_list(self, args: argparse.Namespace) -> None:
     macro_description = "Manage macros\n" "\n" "A macro is similar to an alias, but it can contain argument placeholders."
     macro_epilog = "See also:\n" "  alias"
     macro_parser = argparse_custom.DEFAULT_ARGUMENT_PARSER(description=macro_description, epilog=macro_epilog)
-    macro_subparsers = macro_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    macro_subparsers.required = True
+    macro_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     # Preserve quotes since we are passing strings to other commands
     @with_argparser(macro_parser, preserve_quotes=True)

tests/test_argparse.py

@@ -250,8 +250,7 @@ def test_preservelist(argparse_app):
 
 def _build_has_subcmd_parser() -> cmd2.Cmd2ArgumentParser:
     has_subcmds_parser = cmd2.Cmd2ArgumentParser(description="Tests as_subcmd_to decorator")
-    has_subcmds_subparsers = has_subcmds_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    has_subcmds_subparsers.required = True
+    has_subcmds_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
     return has_subcmds_parser
 
 
@@ -273,8 +272,7 @@ def base_helpless(self, args):
 
     # create the top-level parser for the base command
     base_parser = cmd2.Cmd2ArgumentParser()
-    base_subparsers = base_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    base_subparsers.required = True
+    base_subparsers = base_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     # create the parser for the "foo" subcommand
     parser_foo = base_subparsers.add_parser('foo', help='foo help')

tests/test_argparse_completer.py

@@ -1249,8 +1249,7 @@ def do_custom_completer(self, args: argparse.Namespace) -> None:
 
     # Test as_subcommand_to decorator with custom completer
     top_parser = Cmd2ArgumentParser(description="Top Command")
-    top_subparsers = top_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    top_subparsers.required = True
+    top_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     @with_argparser(top_parser)
     def do_top(self, args: argparse.Namespace) -> None:

tests_isolated/test_commandset/test_argparse_subcommands.py

@@ -35,8 +35,7 @@ def base_helpless(self, args):
 
     # create the top-level parser for the base command
     base_parser = cmd2.Cmd2ArgumentParser()
-    base_subparsers = base_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    base_subparsers.required = True
+    base_subparsers = base_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     # create the parser for the "foo" subcommand
     parser_foo = base_subparsers.add_parser('foo', help='foo help')

tests_isolated/test_commandset/test_commandset.py

@@ -93,8 +93,7 @@ def do_elderberry(self, ns: argparse.Namespace):
     # Test that CommandSet with as_subcommand_to decorator successfully loads
     # during `cmd2.Cmd.__init__()`.
     main_parser = cmd2.Cmd2ArgumentParser(description="Main Command")
-    main_subparsers = main_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND')
-    main_subparsers.required = True
+    main_parser.add_subparsers(dest='subcommand', metavar='SUBCOMMAND', required=True)
 
     @cmd2.with_category('Alone')
     @cmd2.with_argparser(main_parser)