From 075992bcbb92da7ea389201ec05a2617d87ae5f2 Mon Sep 17 00:00:00 2001
From: KtorZ <matthias.benkort@gmail.com>
Date: Tue, 18 Jan 2022 11:47:31 +0100
Subject: [PATCH] Try some on-chain debugging, which does not work but almost.

---
 hydra-plutus/src/Hydra/Contract/Head.hs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/hydra-plutus/src/Hydra/Contract/Head.hs b/hydra-plutus/src/Hydra/Contract/Head.hs
index 700a084b674..f6c2841b7c8 100644
--- a/hydra-plutus/src/Hydra/Contract/Head.hs
+++ b/hydra-plutus/src/Hydra/Contract/Head.hs
@@ -118,8 +118,20 @@ headValidator _ commitAddress oldState input context =
                     traceIfFalse "committed value is not preserved in head" $
                       headOutputValue == collectedValue <> headInputValue
 
+                  checkOutputDatumError =
+                    "unexpected output datum in collectCom, expected utxo hash: "
+                      `appendByteString` utxoHash
+                      `appendByteString` ", actual utxo hash: "
+                      `appendByteString` actualUtxoHash
+
+                  actualUtxoHash = fromMaybe "couldn't find actual hash?" $ do
+                    headOutputDatumHash <- txOutDatumHash headOutput
+                    actualDatum <- findDatum headOutputDatumHash txInfo
+                    Open{utxoHash = actual} <- fromBuiltinData (getDatum actualDatum)
+                    pure actual
+
                   checkOutputDatum =
-                    traceIfFalse "unexpected output datum in collectCom" $
+                    traceIfFalse (decodeUtf8 checkOutputDatumError) $
                       fromMaybe False $ do
                         headOutputDatumHash <- txOutDatumHash headOutput
                         actualDatum <- findDatum headOutputDatumHash txInfo