Avoid "ambiguous option" when only current/deprecated forms match

argparse.ArgumentParser allows to specify partially options:

  nova boot ... --key-nam mykey
  # is equivalent to
  nova boot ... --key-name mykey

an error is raised if the provided prefix matchs 0 or 2+ options:

  nova boot ... --os value
  # raises an "ambiguous option" error because --os could match
  # --os-username, --os_username ...

even if the provided prefix matchs only the current/deprecated
forms of the same attribute:

  nova boot ... --key mykey
  # raises an "ambiguous option" error because --key could match
  # --my-key, --my_key ...

This change extends argparse.ArgumentParser to avoid raising an
"ambiguous option" when the provided prefix matchs only the current and
deprecated forms of the same attribute.

Change-Id: I1089901de769df3312d4a15b6d6e5e60b1ed51e0

novaclient/shell.py

@@ -229,6 +229,23 @@ class NovaClientArgumentParser(argparse.ArgumentParser):
                       'mainp': progparts[0],
                       'subp': progparts[2]})
 
+    def _get_option_tuples(self, option_string):
+        """returns (action, option, value) candidates for an option prefix
+
+        Returns [first candidate] if all candidates refers to current and
+        deprecated forms of the same options: "nova boot ... --key KEY"
+        parsing succeed because --key could only match --key-name,
+        --key_name which are current/deprecated forms of the same option.
+        """
+        option_tuples = (super(NovaClientArgumentParser, self)
+                         ._get_option_tuples(option_string))
+        if len(option_tuples) > 1:
+            normalizeds = [option.replace('_', '-')
+                           for action, option, value in option_tuples]
+            if len(set(normalizeds)) == 1:
+                return option_tuples[:1]
+        return option_tuples
+
 
 class OpenStackComputeShell(object):
 

novaclient/tests/test_shell.py

@@ -37,6 +37,31 @@ FAKE_ENV2 = {'OS_USER_ID': 'user_id',
              'OS_AUTH_URL': 'http://no.where'}
 
 
+class ParserTest(utils.TestCase):
+
+    def setUp(self):
+        super(ParserTest, self).setUp()
+        self.parser = novaclient.shell.NovaClientArgumentParser()
+
+    def test_ambiguous_option(self):
+        self.parser.add_argument('--tic')
+        self.parser.add_argument('--tac')
+
+        try:
+            self.parser.parse_args(['--t'])
+        except SystemExit as err:
+            self.assertEqual(2, err.code)
+        else:
+            self.fail('SystemExit not raised')
+
+    def test_not_really_ambiguous_option(self):
+        # current/deprecated forms of the same option
+        self.parser.add_argument('--tic-tac', action="store_true")
+        self.parser.add_argument('--tic_tac', action="store_true")
+        args = self.parser.parse_args(['--tic'])
+        self.assertTrue(args.tic_tac)
+
+
 class ShellTest(utils.TestCase):
 
     def make_env(self, exclude=None, fake_env=FAKE_ENV):