[commands] Add a way to enable or disable certain commands.

discord/ext/commands/core.py

@@ -66,6 +66,11 @@ class Command:
     pass_context : bool
         A boolean that indicates that the current :class:`Context` should
         be passed as the **first parameter**. Defaults to `False`.
+    enabled : bool
+        A boolean that indicates if the command is currently enabled.
+        If the command is invoked while it is disabled, then
+        :exc:`DisabledCommand` is raised to the :func:`on_command_error`
+        event. Defaults to ``True``.
     checks
         A list of predicates that verifies if the command could be executed
         with the given :class:`Context` as the sole parameter. If an exception
@@ -77,6 +82,7 @@ class Command:
     def __init__(self, name, callback, **kwargs):
         self.name = name
         self.callback = callback
+        self.enabled = kwargs.get('enabled', True)
         self.help = kwargs.get('help')
         self.brief = kwargs.get('brief')
         self.aliases = kwargs.get('aliases', [])
@@ -206,15 +212,18 @@ class Command:
         return True
 
     def _verify_checks(self, ctx):
-        predicates = self.checks
-        if predicates:
-            try:
+        try:
+            if not self.enabled:
+                raise DisabledCommand('{0.name} command is disabled'.format(self))
+
+            predicates = self.checks
+            if predicates:
                 check = all(predicate(ctx) for predicate in predicates)
                 if not check:
                     raise CheckFailure('The check functions for command {0.name} failed.'.format(self))
-            except CommandError as exc:
-                ctx.bot.dispatch('command_error', exc, ctx)
-                return False
+        except CommandError as exc:
+            ctx.bot.dispatch('command_error', exc, ctx)
+            return False
 
         return True
 
@@ -291,6 +300,24 @@ class GroupMixin:
         """
         return self.commands.pop(name, None)
 
+    def get_command(self, name):
+        """Get a :class:`Command` or subclasses from the internal list
+        of commands.
+
+        This could also be used as a way to get aliases.
+
+        Parameters
+        -----------
+        name : str
+            The name of the command to get.
+
+        Returns
+        --------
+        Command or subclass
+            The command that was requested. If not found, returns ``None``.
+        """
+        return self.commands.get(name, None)
+
     def command(self, *args, **kwargs):
         """A shortcut decorator that invokes :func:`command` and adds it to
         the internal command list via :meth:`add_command`.

discord/ext/commands/errors.py

@@ -27,7 +27,8 @@ from discord.errors import DiscordException
 
 
 __all__ = [ 'CommandError', 'MissingRequiredArgument', 'BadArgument',
-           'NoPrivateMessage', 'CheckFailure', 'CommandNotFound' ]
+           'NoPrivateMessage', 'CheckFailure', 'CommandNotFound',
+           'DisabledCommand' ]
 
 class CommandError(DiscordException):
     """The base exception type for all command related errors.
@@ -69,3 +70,7 @@ class NoPrivateMessage(CommandError):
 class CheckFailure(CommandError):
     """Exception raised when the predicates in :attr:`Command.checks` have failed."""
     pass
+
+class DisabledCommand(CommandError):
+    """Exception raised when the command being invoked is disabled."""
+    pass