Merge pull request #928 from python-cmd2/subcmd_aliases

Fixed argparse usage text

1 files changed, 25 insertions, 6 deletions

diff --git a/cmd2/decorators.py b/cmd2/decorators.py
index dc196032..d2fdf9c7 100644
--- a/cmd2/decorators.py
+++ b/cmd2/decorators.py
@@ -85,8 +85,9 @@ def _set_parser_prog(parser: argparse.ArgumentParser, prog: str):
     """
     Recursively set prog attribute of a parser and all of its subparsers so that the root command
     is a command name and not sys.argv[0].
+
     :param parser: the parser being edited
-    :param prog: value for the current parsers prog attribute
+    :param prog: new value for the parser's prog attribute
     """
     # Set the prog value for this parser
     parser.prog = prog
@@ -94,11 +95,29 @@ def _set_parser_prog(parser: argparse.ArgumentParser, prog: str):
     # Set the prog value for the parser's subcommands
     for action in parser._actions:
         if isinstance(action, argparse._SubParsersAction):
-
-            # Set the prog value for each subcommand
-            for sub_cmd, sub_cmd_parser in action.choices.items():
-                sub_cmd_prog = parser.prog + ' ' + sub_cmd
-                _set_parser_prog(sub_cmd_parser, sub_cmd_prog)
+            # Set the _SubParsersAction's _prog_prefix value. That way if its add_parser() method is called later,
+            # the correct prog value will be set on the parser being added.
+            action._prog_prefix = parser.prog
+
+            # The keys of action.choices are subcommand names as well as subcommand aliases. The aliases point to the
+            # same parser as the actual subcommand. We want to avoid placing an alias into a parser's prog value.
+            # Unfortunately there is nothing about an action.choices entry which tells us it's an alias. In most cases
+            # we can filter out the aliases by checking the contents of action._choices_actions. This list only contains
+            # help information and names for the subcommands and not aliases. However, subcommands without help text
+            # won't show up in that list. Since dictionaries are ordered in Python 3.6 and above and argparse inserts the
+            # subcommand name into choices dictionary before aliases, we should be OK assuming the first time we see a
+            # parser, the dictionary key is a subcommand and not alias.
+            processed_parsers = []
+
+            # Set the prog value for each subcommand's parser
+            for subcmd_name, subcmd_parser in action.choices.items():
+                # Check if we've already edited this parser
+                if subcmd_parser in processed_parsers:
+                    continue
+
+                subcmd_prog = parser.prog + ' ' + subcmd_name
+                _set_parser_prog(subcmd_parser, subcmd_prog)
+                processed_parsers.append(subcmd_parser)
 
             # We can break since argparse only allows 1 group of subcommands per level
             break