Should not try to apply decommit tx again

Signed-off-by: Sasha Bogicevic <[email protected]>

hydra-node/src/Hydra/HeadLogic.hs

@@ -472,18 +472,22 @@ onOpenNetworkReqSn env ledger st otherParty sv sn requestedTxIds mDecommitTx =
       unseen -> wait $ WaitOnTxs unseen
 
   requireApplicableDecommitTx cont =
-    case mDecommitTx of
-      Nothing -> cont (confirmedUTxO, Nothing)
-      Just decommitTx ->
-        -- Spec: require ̅S.𝑈 ◦ txω /= ⊥
-        case applyTransactions ledger currentSlot confirmedUTxO [decommitTx] of
-          Left (_, err) ->
-            Error $ RequireFailed $ SnapshotDoesNotApply sn (txId decommitTx) err
-          Right newConfirmedUTxO -> do
-            -- Spec: 𝑈_active ← ̅S.𝑈 ◦ txω \ outputs(txω)
-            let utxoToDecommit = utxoFromTx decommitTx
-            let activeUTxO = newConfirmedUTxO `withoutUTxO` utxoToDecommit
-            cont (activeUTxO, Just utxoToDecommit)
+    -- NOTE: if decommit tx was already applied when we constructed the previous
+    -- snapshot we should not try to apply it again
+    if confUTxOToDecommit == decommitUTxO
+      then cont (confirmedUTxO, decommitUTxO)
+      else case mDecommitTx of
+        Nothing -> cont (confirmedUTxO, Nothing)
+        Just decommitTx ->
+          -- Spec: require ̅S.𝑈 ◦ txω /= ⊥
+          case applyTransactions ledger currentSlot confirmedUTxO [decommitTx] of
+            Left (_, err) ->
+              Error $ RequireFailed $ SnapshotDoesNotApply sn (txId decommitTx) err
+            Right newConfirmedUTxO -> do
+              -- Spec: 𝑈_active ← ̅S.𝑈 ◦ txω \ outputs(txω)
+              let utxoToDecommit = utxoFromTx decommitTx
+              let activeUTxO = newConfirmedUTxO `withoutUTxO` utxoToDecommit
+              cont (activeUTxO, Just utxoToDecommit)
 
   -- NOTE: at this point we know those transactions apply on the localUTxO because they
   -- are part of the localTxs. The snapshot can contain less transactions than the ones
@@ -512,6 +516,12 @@ onOpenNetworkReqSn env ledger st otherParty sv sn requestedTxIds mDecommitTx =
     InitialSnapshot{} -> 0
     ConfirmedSnapshot{snapshot = Snapshot{number}} -> number
 
+  decommitUTxO = utxoFromTx <$> mDecommitTx
+
+  confUTxOToDecommit = case confirmedSnapshot of
+    InitialSnapshot{} -> Nothing
+    ConfirmedSnapshot{snapshot = Snapshot{utxoToDecommit}} -> utxoToDecommit
+
   seenSn = seenSnapshotNumber seenSnapshot
 
   confirmedUTxO = case confirmedSnapshot of

hydra-node/test/Hydra/BehaviorSpec.hs

@@ -18,6 +18,7 @@ import Control.Concurrent.Class.MonadSTM (
  )
 import Control.Monad.Class.MonadAsync (Async, MonadAsync (async), cancel, forConcurrently_)
 import Control.Monad.IOSim (IOSim, runSimTrace, selectTraceEventsDynamic)
+import Data.Aeson (encode)
 import Data.List ((!!))
 import Data.List qualified as List
 import Hydra.API.ClientInput
@@ -460,19 +461,6 @@ spec = parallel $ do
 
                 waitUntil [n1, n2] $ DecommitFinalized{headId = testHeadId, decommitTxId = 1}
 
-    it "can close with decommit in flight" $
-      shouldRunInSim $ do
-        withSimulatedChainAndNetwork $ \chain ->
-          withHydraNode aliceSk [bob] chain $ \n1 -> do
-            withHydraNode bobSk [alice] chain $ \n2 -> do
-              openHead chain n1 n2
-              let decommitTx = SimpleTx 1 (utxoRef 2) (utxoRef 42)
-              send n2 (Decommit{decommitTx})
-              send n1 Close
-              waitUntil [n1, n2] $ ReadyToFanout{headId = testHeadId}
-              send n1 Fanout
-              waitUntil [n1, n2] $ HeadIsFinalized{headId = testHeadId, utxo = utxoRefs [1, 2]}
-
     it "fanout utxo is correct after a decommit" $
       shouldRunInSim $ do
         withSimulatedChainAndNetwork $ \chain ->
@@ -561,7 +549,7 @@ spec = parallel $ do
                 simulateCommit chain (alice, utxoRef 1)
 
           logs = selectTraceEventsDynamic @_ @(HydraNodeLog SimpleTx) result
-
+      print $ encode logs
       logs `shouldContain` [BeginEffect alice 1 0 (ClientEffect $ HeadIsInitializing testHeadId $ fromList [alice])]
       logs `shouldContain` [EndEffect alice 1 0]
 
@@ -733,7 +721,10 @@ simulatedChainAndNetwork initialChainState = do
                 Chain
                   { postTx = \tx -> do
                       now <- getCurrentTime
-                      createAndYieldEvent nodes history localChainState $ toOnChainTx now tx
+                      -- Only observe "after one block"
+                      void . async $ do
+                        threadDelay blockTime
+                        createAndYieldEvent nodes history localChainState $ toOnChainTx now tx
                   , draftCommitTx = \_ -> error "unexpected call to draftCommitTx"
                   , submitTx = \_ -> error "unexpected call to submitTx"
                   }