Decorators: pass bound arguments to callable

Bound arguments are more convenient to work with than the raw args
and kwargs.

1 files changed, 12 insertions, 6 deletions

diff --git a/bot/decorators.py b/bot/decorators.py
index f581e66d2..7f58abd1c 100644
--- a/bot/decorators.py
+++ b/bot/decorators.py
@@ -18,9 +18,10 @@ log = logging.getLogger(__name__)
 __lock_dicts = defaultdict(WeakValueDictionary)
 
 Argument = t.Union[int, str]
-_IdCallable = t.Callable[..., t.Hashable]
-_IdAwaitable = t.Callable[..., t.Awaitable[t.Hashable]]
-ResourceId = t.Union[t.Hashable, _IdCallable, _IdAwaitable]
+BoundArgs = t.OrderedDict[str, t.Any]
+_IdCallableReturn = t.Union[t.Hashable, t.Awaitable[t.Hashable]]
+_IdCallable = t.Callable[[BoundArgs], _IdCallableReturn]
+ResourceId = t.Union[t.Hashable, _IdCallable]
 
 
 def in_whitelist(
@@ -108,8 +109,8 @@ def mutually_exclusive(namespace: t.Hashable, resource_id: ResourceId) -> t.Call
     `namespace` is an identifier used to prevent collisions among resource IDs.
 
     `resource_id` identifies a resource on which to perform a mutually exclusive operation.
-    It may also be a callable or awaitable which will return the resource ID given the decorated
-    function's args and kwargs.
+    It may also be a callable or awaitable which will return the resource ID given an ordered
+    mapping of the parameters' names to arguments' values.
 
     If decorating a command, this decorator must go before (below) the `command` decorator.
     """
@@ -121,8 +122,13 @@ def mutually_exclusive(namespace: t.Hashable, resource_id: ResourceId) -> t.Call
             log.trace(f"{name}: mutually exclusive decorator called")
 
             if callable(resource_id):
+                log.trace(f"{name}: binding args to signature")
+                sig = inspect.signature(func)
+                bound_args = sig.bind(*args, **kwargs)
+                bound_args.apply_defaults()
+
                 log.trace(f"{name}: calling the given callable to get the resource ID")
-                id_ = resource_id(*args, **kwargs)
+                id_ = resource_id(bound_args.arguments)
 
                 if inspect.isawaitable(id_):
                     log.trace(f"{name}: awaiting to get resource ID")