[worker] simplify exception catching

src/Async/Worker.hs

@@ -39,7 +39,7 @@ import Async.Worker.Broker
 import Async.Worker.Types
 import Control.Concurrent.STM (atomically)
 import Control.Concurrent.STM.TVar (readTVarIO, newTVarIO, writeTVar)
-import Control.Exception.Safe (catch, fromException, throwIO, SomeException, Exception)
+import Control.Exception.Safe (catches, Handler(..), throwIO, SomeException, Exception)
 import Control.Monad (forever, void, when)
 import Debug.Trace (traceStack)
 import System.Timeout qualified as Timeout
@@ -70,16 +70,14 @@ run state@(State { .. }) = do
       -- exception handling.
       mBrokerMessageTVar <- newTVarIO Nothing -- :: IO (TVar (Maybe (BrokerMessage b (Job a))))
       
-      catch (do
+      catches (do
                 brokerMessage <- readMessageWaiting broker queueName
                 atomically $ writeTVar mBrokerMessageTVar (Just brokerMessage)
                 handleMessage state brokerMessage
                 callWorkerJobEvent onJobFinish state brokerMessage
-                atomically $ writeTVar mBrokerMessageTVar Nothing
-            ) (\err -> do
+            ) [
+        Handler $ \(_err :: KillWorkerSafely) -> do
           mBrokerMessage <- readTVarIO mBrokerMessageTVar
-        case fromException err of
-          Just KillWorkerSafely -> do
           case mBrokerMessage of
             Just brokerMessage -> do
               let job = toA $ getMessage brokerMessage
@@ -97,13 +95,15 @@ run state@(State { .. }) = do
               -- kill worker
               throwIO KillWorkerSafely
             Nothing -> pure ()
-          Nothing -> case fromException err of
-            Just jt@(JobTimeout {}) -> handleTimeoutError state jt
-            Nothing -> case mBrokerMessage of
+        , Handler $ \(err :: JobTimeout b a) -> handleTimeoutError state err
+        , Handler $ \err -> do
+            mBrokerMessage <- readTVarIO mBrokerMessageTVar
+            case mBrokerMessage of
               Just brokerMessage -> do
                 callWorkerJobEvent onJobError state brokerMessage
                 handleJobError state brokerMessage
-              _ -> handleUnknownError state err)
+              Nothing -> handleUnknownError state err
+        ]
  
 handleMessage :: (HasWorkerBroker b a) => State b a -> BrokerMessage b (Job a) -> IO ()
 handleMessage state@(State { .. }) brokerMessage = do