Fix build issues

Author: Jimbo4350

cardano-testnet/src/Testnet/Runtime.hs

@@ -37,7 +37,7 @@ import           Data.Algorithm.Diff
 import           Data.Algorithm.DiffOutput
 import           Data.Bifunctor (first)
 import qualified Data.ByteString.Lazy.Char8 as BSC
-import           Data.List (isInfixOf)
+import           Data.List (isInfixOf, uncons)
 import qualified Data.List as List
 import           GHC.Stack
 import qualified GHC.Stack as GHC
@@ -297,8 +297,11 @@ startLedgerNewEpochStateLogging testnetRuntime tmpWorkspace = withFrozenCallStac
   liftIOAnnotated $ IO.doesFileExist logFile >>= \case
     True -> return () 
     False -> liftIO $ appendFile logFile ""
-  
-  let socketPath =  H.sprocketSystemName $ head (testnetSprockets testnetRuntime)
+
+  let socketPath = case uncons (testnetSprockets testnetRuntime) of
+        Just (sprocket, _) -> H.sprocketSystemName sprocket
+        Nothing            -> throwString "No testnet sprocket available"
+
   let act = runExceptT $
               foldEpochState
                 (configurationFile testnetRuntime)

cardano-testnet/src/Testnet/Start/Cardano.hs

@@ -50,6 +50,7 @@ import qualified Data.ByteString.Lazy as LBS
 import           Data.Default.Class (def)
 import           Data.Either
 import           Data.Functor
+import           Data.List (uncons)
 import           Data.MonoTraversable (Element, MonoFunctor, omap)
 import qualified Data.Text as Text
 import           Data.Time (diffUTCTime)
@@ -400,7 +401,9 @@ cardanoTestnet
 
   let tempBaseAbsPath = makeTmpBaseAbsPath $ TmpAbsolutePath tmpAbsPath
 
-  let node1sprocket = head $ testnetSprockets runtime
+  node1sprocket <- case uncons $ testnetSprockets runtime of
+        Just (sprocket, _) -> pure sprocket
+        Nothing            -> throwString "No testnet sprocket available"
   execConfig <- mkExecConfig tempBaseAbsPath node1sprocket testnetMagic
 
   forM_ wallets $ \wallet -> do