Return a Maybe CRC when taking a V2 snapshot in preparation for LSM

Author: jasagredo

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/LedgerDB/V2/InMemory.hs

@@ -139,7 +139,7 @@ newInMemoryLedgerTablesHandle tracer someFS@(SomeHasFS hasFS) l = do
           guardClosed h $
             \values ->
               withFile hasFS (mkFsPath [snapshotName, "tables", "tvar"]) (WriteMode MustBeNew) $ \hf ->
-                fmap snd $
+                fmap (Just . snd) $
                   hPutAllCRC hasFS hf $
                     CBOR.toLazyByteString $
                       valuesMKEncoder hint values

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/LedgerDB/V2/LedgerSeq.hs

@@ -96,7 +96,7 @@ data LedgerTablesHandle m l = LedgerTablesHandle
   -- The first argument has to be the ledger state before applying
   -- the block, the second argument should be the ledger state after
   -- applying a block. See 'CanUpgradeLedgerTables'.
-  , takeHandleSnapshot :: !(l EmptyMK -> String -> m CRC)
+  , takeHandleSnapshot :: !(l EmptyMK -> String -> m (Maybe CRC))
   , tablesSize :: !(m (Maybe Int))
   -- ^ Consult the size of the ledger tables in the database. This will return
   -- 'Nothing' in backends that do not support this operation.