Fix a non catched exception when an invalid prefix is given to --prefix

app/ip6addr.hs

@@ -1,7 +1,10 @@
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RecordWildCards   #-}
+{-# LANGUAGE OverloadedStrings   #-}
+{-# LANGUAGE RecordWildCards     #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
+import           Control.Exception
 import           Control.Monad       (replicateM_)
+import           Data.Maybe
 import qualified Data.Text           as T (pack)
 import qualified Data.Text.IO        as TIO (hPutStrLn, putStrLn)
 import           Data.Version        (showVersion)
@@ -11,27 +14,6 @@ import           System.Exit
 import           System.IO           (stderr)
 import           Text.IPv6Addr
 
-data Output
-  = Canonical
-  | NoIPv4
-  | FullLength
-  | PTR
-  | UNC
-  | Random
-  deriving (Eq)
-
-data Options =
-  Options
-    { showver  :: !Bool
-    , output   :: !Output
-    , quantity :: !Int
-    , prefix   :: !String
-    , address  :: !String
-    }
-
-showVer :: String
-showVer = "ip6addr v" <> showVersion version <> " (c) Michel Boucey 2011-2024"
-
 main :: IO ()
 main = do
   Options{..} <- execParser opts
@@ -47,10 +29,12 @@ main = do
         Random     -> replicateM_ quantity (putRandAddr prefix) >> exitSuccess
   where
     putRandAddr p = do
-      r <- randIPv6AddrWithPrefix (if p == mempty then Nothing else Just (T.pack p))
-      case r of
-        Just a  -> TIO.putStrLn (unIPv6Addr a)
-        Nothing -> TIO.putStrLn "Bad prefix"
+      let p' = T.pack p
+      t <- try $ randIPv6AddrWithPrefix (if p == mempty then Nothing else Just p')
+      case t of
+        Right a                   -> TIO.putStrLn (unIPv6Addr $ fromJust a)
+        Left (_ :: SomeException) ->
+          TIO.putStrLn (p' <> " is an invalid prefix") >> exitFailure
     out t i o =
       if i /= mempty
         then do
@@ -63,6 +47,27 @@ main = do
     maybeUNC t = toUNC <$> maybePureIPv6Addr t
     maybeIP6ARPA t = toIP6ARPA <$> maybeFullIPv6Addr t
 
+showVer :: String
+showVer = "ip6addr v" <> showVersion version <> " (c) Michel Boucey 2011-2024"
+
+data Output
+  = Canonical
+  | NoIPv4
+  | FullLength
+  | PTR
+  | UNC
+  | Random
+  deriving (Eq)
+
+data Options =
+  Options
+    { showver  :: !Bool
+    , output   :: !Output
+    , quantity :: !Int
+    , prefix   :: !String
+    , address  :: !String
+    }
+
 opts :: ParserInfo Options
 opts = info (parseOptions <**> helper)
   ( fullDesc