properly encode non-ASCII characters with encodeString

src/Network/GemServ.hs

@@ -33,9 +33,9 @@ module Network.GemServ (
 ) where
 
 import qualified Data.ByteString as BS
-import Data.ByteString.Builder (charUtf8, toLazyByteString)
+import Data.ByteString.Builder (charUtf8, stringUtf8, toLazyByteString)
 import qualified Data.ByteString.Lazy as BSL
-import Data.Char (ord, toLower)
+import Data.Char (chr, ord, toLower)
 import Data.List (find, intercalate)
 import Data.Maybe (fromJust)
 import qualified Data.Text as T
@@ -58,17 +58,20 @@ encodeRequest req =
 
 -- | add required escape sequences to a string
 escapeString :: String -> String
-escapeString = concatMap $ \ch ->
+escapeString = concatMap
+  ( \n -> let ch = chr $ fromIntegral n in
     if ch `elem` unescaped
     then [ch]
-  else '%' : toHex ch
+    else '%' : toHex n
+  ) . BSL.unpack . toLazyByteString . stringUtf8
   where
     unescaped = ['0'..'9'] ++ ['A'..'Z'] ++ ['a'..'z'] ++ "~-_."
-    toHex ch  = let
-      n    = ord ch
+    toHex =
+      ( \n -> let
         high = n `div` 16
         low  = n `mod` 16
         in [hexDigits !! high, hexDigits !! low]
+      ) . fromIntegral
 
 -- | decode an escaped string back to its original value
 unescapeString :: String -> Maybe String

test/Network/GemServSpec.hs

@@ -75,6 +75,7 @@ escapeStringSpec = describe "escapeString" $ mapM_
   --  input,               expected
   [ ( "~foo-bar_baz.quux", "~foo-bar_baz.quux"        )
   , ( "foo:/?=&#%",        "foo%3a%2f%3f%3d%26%23%25" )
+  , ( "foo\xe9",           "foo%c3%a9"                )
   ]
 
 unescapeStringSpec :: Spec