cli: Handle missing commands gracefully

Previously when leapp was executed but no cli commands were installed,
the leapp execution failed with an exception.

This patch will add specific handling to this particular scenario and
return a 1 exit code.

Co-authored-by: Petr Stodůlka <[email protected]>
Co-authored-by: Inessa Vasilevskaya <[email protected]>

Signed-off-by: Vinzenz Feenstra <[email protected]>

leapp/cli/__init__.py

@@ -1,11 +1,12 @@
-
 import os
 import pkgutil
 import socket
 import sys
+import textwrap
 
 from leapp import VERSION
 from leapp.cli import commands
+from leapp.exceptions import UnknownCommandError
 from leapp.utils.clicmd import command
 
 
@@ -40,4 +41,13 @@ def main():
 
     os.environ['LEAPP_HOSTNAME'] = socket.getfqdn()
     _load_commands(cli.command)
-    cli.command.execute('leapp version {}'.format(VERSION))
+    try:
+        cli.command.execute('leapp version {}'.format(VERSION))
+    except UnknownCommandError as e:
+        print(textwrap.dedent('''
+        Command "{CMD}" is unknown.
+        Most likely there is a typo in the command or particular leapp repositories that provide this command
+        are not present on the system.
+        You can try to install the missing content e.g. by the following command: `dnf install 'leapp-command({CMD})'`
+        '''.format(CMD=e.requested)))
+        sys.exit(1)

leapp/exceptions.py

@@ -102,6 +102,12 @@ class CommandDefinitionError(LeappError):
     pass
 
 
+class UnknownCommandError(LeappError):
+    def __init__(self, command):
+        super().__init__('Unknown command: {}'.format(command))
+        self.requested = command
+
+
 class LeappRuntimeError(LeappError):
     pass
 

leapp/utils/clicmd.py

@@ -1,12 +1,12 @@
 import functools
 import os
 import sys
-
-from argparse import ArgumentParser, _SubParsersAction, RawDescriptionHelpFormatter
+from argparse import (ArgumentParser, RawDescriptionHelpFormatter,
+                      _SubParsersAction)
 
 import six
-
-from leapp.exceptions import CommandDefinitionError, UsageError, CommandError
+from leapp.exceptions import (CommandDefinitionError, CommandError,
+                              UnknownCommandError, UsageError)
 
 
 class _LeappArgumentParser(ArgumentParser):
@@ -23,6 +23,7 @@ class _LeappHelpFormatter(RawDescriptionHelpFormatter):
     """
     Capitalizes section headings in the help output
     """
+
     def start_section(self, heading):
         return super(_LeappHelpFormatter, self).start_section(heading.capitalize())
 
@@ -38,6 +39,7 @@ class _SubParserActionOverride(_SubParsersAction):
 
     The additional code will not be executed if python 2.7.9 or higher is found.
     """
+
     def __call__(self, parser, namespace, values, option_string=None):
         super(_SubParserActionOverride, self).__call__(parser, namespace, values, option_string)
         if sys.version_info >= (2, 7, 9):
@@ -54,6 +56,7 @@ class Command(object):
     """
     Command implements a convenient command-based argument parsing the framework.
     """
+
     def __init__(self, name, target=None, help='', description=None):  # noqa; pylint: disable=redefined-builtin
         """
         :param name: Name of the sub command
@@ -100,8 +103,10 @@ def execute(self, version):
         args, leftover = parser.parse_known_args()
         if leftover:
             cmdname = args.prog.split()[-1]
-            # NOTE(ivasilev) No vetting of cmdname is necessary here as unless a proper leapp subcommand was
-            # invocated parser.parse_known_args() would have thrown an exception
+            if cmdname not in self._sub_commands:
+                cmdname = leftover[0]
+            if cmdname not in self._sub_commands:
+                raise UnknownCommandError(cmdname)
             self._sub_commands[cmdname].parser.error(leftover)
         args.func(args)