Allow eval almost everywhere

Adds a check to blacklist a command only in a specific context, with an option for a role override. The check is applied to the eval command to blacklist it only from python-general.

2 files changed, 44 insertions, 5 deletions

diff --git a/bot/decorators.py b/bot/decorators.py
index 1d30317ef..5a49d64fc 100644
--- a/bot/decorators.py
+++ b/bot/decorators.py
@@ -11,7 +11,7 @@ from discord.ext.commands import Cog, Context
 
 from bot.constants import Channels, DEBUG_MODE, RedirectOutput
 from bot.utils import function
-from bot.utils.checks import in_whitelist_check
+from bot.utils.checks import InWhitelistCheckFailure, in_whitelist_check
 from bot.utils.function import command_wraps
 
 log = logging.getLogger(__name__)
@@ -45,6 +45,45 @@ def in_whitelist(
     return commands.check(predicate)
 
 
+def not_in_blacklist(
+    *,
+    channels: t.Container[int] = (),
+    categories: t.Container[int] = (),
+    roles: t.Container[int] = (),
+    override_roles: t.Container[int] = (),
+    redirect: t.Optional[int] = Channels.bot_commands,
+    fail_silently: bool = False,
+) -> t.Callable:
+    """
+    Check if a command was not issued in a blacklisted context.
+
+    The blacklists that can be provided are:
+
+    - `channels`: a container with channel ids for blacklisted channels
+    - `categories`: a container with category ids for blacklisted categories
+    - `roles`: a container with role ids for blacklisted roles
+
+    If the command was invoked in a context that was blacklisted, the member is either
+    redirected to the `redirect` channel that was passed (default: #bot-commands) or simply
+    told that they're not allowed to use this particular command (if `None` was passed).
+
+    The blacklist can be overridden through the roles specified in `override_roles`.
+    """
+    def predicate(ctx: Context) -> bool:
+        """Check if command was issued in a blacklisted context."""
+        not_blacklisted = not in_whitelist_check(ctx, channels, categories, roles, fail_silently=True)
+        overridden = in_whitelist_check(ctx, roles=override_roles, fail_silently=True)
+
+        success = not_blacklisted or overridden
+
+        if not success and not fail_silently:
+            raise InWhitelistCheckFailure(redirect)
+
+        return success
+
+    return commands.check(predicate)
+
+
 def has_no_roles(*roles: t.Union[str, int]) -> t.Callable:
     """
     Returns True if the user does not have any of the roles specified.
diff --git a/bot/exts/utils/snekbox.py b/bot/exts/utils/snekbox.py
index 9f480c067..6ea588888 100644
--- a/bot/exts/utils/snekbox.py
+++ b/bot/exts/utils/snekbox.py
@@ -13,7 +13,7 @@ from discord.ext.commands import Cog, Context, command, guild_only
 
 from bot.bot import Bot
 from bot.constants import Categories, Channels, Roles, URLs
-from bot.decorators import in_whitelist
+from bot.decorators import not_in_blacklist
 from bot.utils import send_to_paste_service
 from bot.utils.messages import wait_for_deletion
 
@@ -39,8 +39,8 @@ RAW_CODE_REGEX = re.compile(
 MAX_PASTE_LEN = 10000
 
 # `!eval` command whitelists
-EVAL_CHANNELS = (Channels.bot_commands, Channels.esoteric)
-EVAL_CATEGORIES = (Categories.help_available, Categories.help_in_use, Categories.voice)
+NO_EVAL_CHANNELS = (Channels.python_general,)
+NO_EVAL_CATEGORIES = ()
 EVAL_ROLES = (Roles.helpers, Roles.moderators, Roles.admins, Roles.owners, Roles.python_community, Roles.partners)
 
 SIGKILL = 9
@@ -280,7 +280,7 @@ class Snekbox(Cog):
 
     @command(name="eval", aliases=("e",))
     @guild_only()
-    @in_whitelist(channels=EVAL_CHANNELS, categories=EVAL_CATEGORIES, roles=EVAL_ROLES)
+    @not_in_blacklist(channels=NO_EVAL_CHANNELS, categories=NO_EVAL_CATEGORIES, override_roles=EVAL_ROLES)
     async def eval_command(self, ctx: Context, *, code: str = None) -> None:
         """
         Run Python code and get the results.