feat: on_command_error event (#949)

* feat: on_command_error event

* docs: document on_command_error

Author: Toricane

docs/events.rst

@@ -54,6 +54,7 @@ There are several different internal events:
     - ``on_start``
     - ``on_interaction``
     - ``on_command``
+    - ``on_command_error``
     - ``on_component``
     - ``on_autocomplete``
     - ``on_modal``
@@ -100,6 +101,16 @@ Using this event, you will have to manually check everything, from name to wheth
 options or anything else - everything will be in the raw context and you will have to search for it
 
 
+Event: ``on_command_error``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+This event fires when the following conditions are met:
+
+1. There is an error in the command (or subcommand within the command)
+2. There is no error callback assigned to that command
+
+The function takes in two arguments, one of the type ``CommandContext``, and the other contains the error.
+
+
 Event: ``on_component``
 ^^^^^^^^^^^^^^^^^^^^^^
 This event fires on any Component used (for now, those are Buttons and Select Menus).

interactions/client/bot.py

@@ -456,9 +456,11 @@ def __resolve_commands(self) -> None:
             if cmd.resolved:
                 continue
 
+            cmd.listener = self._websocket._dispatch
+
             if cmd.default_scope and self._default_scope:
                 cmd.scope = (
-                    cmd.scope.extend(cmd.default_scope)
+                    cmd.scope.extend(self._default_scope)
                     if isinstance(cmd.scope, list)
                     else self._default_scope
                 )

interactions/client/models/command.py

@@ -15,6 +15,7 @@
 from ..enums import ApplicationCommandType, Locale, OptionType, PermissionType
 
 if TYPE_CHECKING:
+    from ...api.dispatch import Listener
     from ..bot import Extension
     from ..context import CommandContext
 
@@ -396,7 +397,8 @@ class Command(DictSerializerMixin):
     :ivar Dict[str, Union[Callable[..., Awaitable], str]] autocompletions: The dictionary of autocompletions for the command.
     :ivar Optional[str] recent_group: The name of the group most recently utilized.
     :ivar bool resolved: Whether the command is synced. Defaults to ``False``.
-    :ivar Extension extension: The extension that the command belongs to, if any.
+    :ivar Optional[Extension] extension: The extension that the command belongs to, if any.
+    :ivar Optional[Listener] listener: The listener, used for dispatching command errors.
     """
 
     coro: Callable[..., Awaitable] = field()
@@ -419,7 +421,8 @@ class Command(DictSerializerMixin):
     recent_group: Optional[str] = field(default=None, init=False)
     error_callback: Optional[Callable[..., Awaitable]] = field(default=None, init=False)
     resolved: bool = field(default=False, init=False)
-    extension: "Extension" = field(default=None, init=False)
+    extension: Optional["Extension"] = field(default=None, init=False)
+    listener: Optional["Listener"] = field(default=None, init=False)
 
     def __attrs_post_init__(self) -> None:
         if self.name is MISSING:
@@ -837,17 +840,19 @@ async def __call(
         except CancelledError:
             pass
         except Exception as e:
-            if not self.error_callback:
-                raise e
-
-            num_params = len(signature(self.error_callback).parameters)
+            if self.error_callback:
+                num_params = len(signature(self.error_callback).parameters)
 
-            if num_params == (3 if self.extension else 2):
-                await self.error_callback(ctx, e)
-            elif num_params == (4 if self.extension else 3):
-                await self.error_callback(ctx, e, _res)
+                if num_params == (3 if self.extension else 2):
+                    await self.error_callback(ctx, e)
+                elif num_params == (4 if self.extension else 3):
+                    await self.error_callback(ctx, e, _res)
+                else:
+                    await self.error_callback(ctx, e, _res, *args, **kwargs)
+            elif self.listener and "on_command_error" in self.listener.events:
+                self.listener.dispatch("on_command_error", ctx, e)
             else:
-                await self.error_callback(ctx, e, _res, *args, **kwargs)
+                raise e
 
             return StopCommand
 
@@ -888,15 +893,17 @@ async def wrapper(ctx: "CommandContext", *args, **kwargs):
             except CancelledError:
                 pass
             except Exception as e:
-                if self.has_subcommands or not self.error_callback:
-                    raise e
-
-                num_params = len(signature(self.error_callback).parameters)
-
-                if num_params == (3 if self.extension else 2):
-                    await self.error_callback(ctx, e)
+                if self.error_callback:
+                    num_params = len(signature(self.error_callback).parameters)
+
+                    if num_params == (3 if self.extension else 2):
+                        await self.error_callback(ctx, e)
+                    else:
+                        await self.error_callback(ctx, e, *args, **kwargs)
+                elif self.listener and "on_command_error" in self.listener.events:
+                    self.listener.dispatch("on_command_error", ctx, e)
                 else:
-                    await self.error_callback(ctx, e, *args, **kwargs)
+                    raise e
 
                 return StopCommand