feat: isLocked

src/Data.Async.Class.purs

@@ -2,7 +2,8 @@ module Data.Async.Class where
 
 import Prelude
 
-import Data.Maybe (Maybe)
+import Data.Foldable (for_)
+import Data.Maybe (Maybe, isNothing)
 import Effect.Aff.Class (class MonadAff)
 
 -- | Acquire a lock that guarantees access to mutable state
@@ -32,6 +33,13 @@ class AsyncStateLock m lock | lock -> m where
   -- | `unlock` has been invoked.
   unlock :: forall async a. MonadAff async => m a -> lock a -> async Unit
 
+-- | Returns whether a lock is currently held
+isLocked :: forall async a l g. MonadAff async => AsyncStateLock l g => l a -> async Boolean
+isLocked l = do
+  guard :: Maybe (g a) <- tryLock l
+  for_ guard (unlock l)
+  pure $ isNothing guard
+
 -- | A lock type that supports writing data to the mutable state.
 -- |
 -- | Writable locks must also be Readable.