[commands] fix a two bugs related to command groupings + tests

1. The shortest possible match for a single command was an empty string.
2. Group matching was overly greedy, and would allow extraneous
characters at the end of the group match.

disco/bot/bot.py

@@ -210,7 +210,7 @@ class Bot(LoggingClass):
         #  abbreviations that don't conflict with eachother.
         possible = {}
         for group in groups:
-            for index in range(len(group)):
+            for index in range(1, len(group)):
                 current = group[:index]
                 if current in possible:
                     possible[current] = None

disco/bot/command.py

@@ -247,7 +247,8 @@ class Command(object):
             group = ''
             if self.group:
                 if self.group in self.plugin.bot.group_abbrev:
-                    group = '{}(?:\w+)? '.format(self.plugin.bot.group_abbrev.get(self.group))
+                    rest = self.plugin.bot.group_abbrev[self.group]
+                    group = '{}(?:{}) '.format(rest, ''.join(c + u'?' for c in self.group[len(rest):]))
                 else:
                     group = self.group + ' '
             return ('^{}({})' if grouped else '^{}(?:{})').format(

tests/test_bot.py

@@ -5,6 +5,10 @@ from disco.bot.bot import Bot
 from disco.bot.command import Command
 
 
+class Object(object):
+    pass
+
+
 class MockBot(Bot):
     @property
     def commands(self):
@@ -27,6 +31,10 @@ class TestBot(TestCase):
             'copez': 'cope',
         })
 
+        self.assertDictEqual(self.bot.compute_group_abbrev(['test']), {
+            'test': 't',
+        })
+
     def test_command_abbreivation_conflicting(self):
         groups = ['cat', 'cap', 'caz', 'cas']
         result = self.bot.compute_group_abbrev(groups)
@@ -45,3 +53,19 @@ class TestBot(TestCase):
         match = self.bot._commands[0].compiled_regex.match('test0 123 456')
         self.assertEqual(match.group(1).strip(), 'test0')
         self.assertEqual(match.group(2).strip(), '123 456')
+
+    def test_command_grouping_greadyness(self):
+        plugin = Object()
+        plugin.bot = self.bot
+
+        self.bot._commands = [
+            Command(plugin, None, 'a', group='test'),
+            Command(plugin, None, 'b', group='test')
+        ]
+
+        self.bot.recompute()
+        self.assertNotEqual(self.bot.command_matches_re.match('test a'), None)
+        self.assertNotEqual(self.bot.command_matches_re.match('te a'), None)
+        self.assertNotEqual(self.bot.command_matches_re.match('t b'), None)
+        self.assertEqual(self.bot.command_matches_re.match('testing b'), None)
+        self.assertEqual(self.bot.command_matches_re.match('testlmao a'), None)