king: error message for lock file

pkg/hs/urbit-king/lib/Urbit/Vere/LockFile.hs

@@ -6,25 +6,42 @@ module Urbit.Vere.LockFile (lockFile) where
 
 import Urbit.Prelude
 
+import Urbit.King.App.Class
+
 import Data.Default                (def)
 import RIO.Directory               (createDirectoryIfMissing)
 import System.IO.LockFile.Internal (LockingParameters(..), RetryStrategy(..),
-                                    lock, unlock)
+                                    LockingException(..), lock, unlock)
 
 --------------------------------------------------------------------------------
 
-lockFile :: HasLogFunc e => FilePath -> RAcquire e ()
+lockFile :: (HasLogFunc e, HasStderrLogFunc e) => FilePath -> RAcquire e ()
 lockFile pax = void $ mkRAcquire start stop
   where
     fil = pax <> "/.vere.lock"
 
     stop handle = do
-        logInfo $ display @Text $ ("Releasing lock file: " <> pack fil)
-        io $ unlock fil handle
+      logInfo $ display @Text $ ("Releasing lock file: " <> pack fil)
+      io $ unlock fil handle
 
     params = def { retryToAcquireLock = No }
 
     start = do
         createDirectoryIfMissing True pax
         logInfo $ display @Text $ ("Taking lock file: " <> pack fil)
-        io (lock params fil)
+        handle failure $ io (lock params fil)
+
+    failure (e :: LockingException) = do
+      logStderr $ logError $ display @Text $
+        "Cannot acquire lock file " <> pack fil <> "."
+      logStderr $ logError $
+        "Please make sure there are no other instances of this ship running, "
+        <> "then try again."
+      logStderr $ logError $
+        "If you are sure, you can delete the file and try again."
+      throwIO e
+
+logStderr :: HasStderrLogFunc e => RIO LogFunc a -> RIO e a
+logStderr action = do
+  logFunc <- view stderrLogFuncL
+  runRIO logFunc action