Common.hs: avoid using Opt.auto to avoid overflows going silent

cardano-cli/src/Cardano/CLI/EraBased/Options/Common.hs

@@ -4,6 +4,7 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
 
 {- HLINT ignore "Move brackets to avoid $" -}
 {- HLINT ignore "Use <$>" -}
@@ -28,9 +29,11 @@ import qualified Ouroboros.Network.Protocol.LocalStateQuery.Type as Consensus
 import           Control.Monad (mfilter)
 import qualified Data.Aeson as Aeson
 import           Data.Bifunctor
+import           Data.Bits (Bits, toIntegralSized)
 import           Data.ByteString (ByteString)
 import qualified Data.ByteString.Base16 as B16
 import qualified Data.ByteString.Char8 as BSC
+import           Data.Data (Proxy (..), Typeable, typeRep)
 import           Data.Foldable
 import           Data.Functor (($>))
 import qualified Data.IP as IP
@@ -3180,9 +3183,24 @@ pMaxTransactionSize =
       , Opt.help "Maximum transaction size."
       ]
 
+-- | @integralReader@ is a reader for a word of type @a@. When it fails
+-- parsing, it provides a nice error message. This custom reader is needed
+-- to avoid the overflow issues of 'Opt.auto' described in https://github.com/IntersectMBO/cardano-cli/issues/860.
+integralReader :: forall a. (Typeable a, Integral a, Bits a) => ReadM a
+integralReader =
+  readerFromParsecParser parsecParser
+ where
+  parsecParser :: Parsec.Parser a
+  parsecParser = do
+    i <- decimal
+    case toIntegralSized i of
+      Nothing -> fail $ "Cannot parse " <> show i <> " as a " <> typeName
+      Just n -> return n
+  typeName = show $ typeRep (Proxy @a)
+
 pMaxBlockHeaderSize :: Parser Word16
 pMaxBlockHeaderSize =
-  Opt.option Opt.auto $
+  Opt.option integralReader $
     mconcat
       [ Opt.long "max-block-header-size"
       , Opt.metavar "WORD16"