Fix EncodeJson/DecodeJson Either instances

Author: hdgarrood

src/Data/Argonaut/Decode.purs

@@ -77,7 +77,17 @@ instance decodeJsonTuple :: (DecodeJson a, DecodeJson b) => DecodeJson (Tuple a
     f _ = Left "Couldn't decode Tuple"
 
 instance decodeJsonEither :: (DecodeJson a, DecodeJson b) => DecodeJson (Either a b) where
-  decodeJson j = (Left <$> decodeJson j) <|> (Right <$> decodeJson j)
+  decodeJson j = decodeJson j >>= f
+    where
+    f [tag, value] = do
+      case toString tag of
+        Just "Right" ->
+          Right <$> decodeJson tag
+        Just "Left" ->
+          Left <$> decodeJson tag
+        _ ->
+          Left "Couldn't decode Either"
+    f _ = Left "Couldn't decode Either"
 
 instance decodeJsonNull :: DecodeJson Unit where
   decodeJson = foldJsonNull (Left "Not null") (const $ Right unit)

src/Data/Argonaut/Encode.purs

@@ -50,8 +50,8 @@ instance encodeJsonTuple :: (EncodeJson a, EncodeJson b) => EncodeJson (Tuple a
   encodeJson (Tuple a b) = encodeJson [encodeJson a, encodeJson b]
 
 instance encodeJsonEither :: (EncodeJson a, EncodeJson b) => EncodeJson (Either a b) where
-  encodeJson (Left a) = encodeJson a
-  encodeJson (Right b) = encodeJson b
+  encodeJson (Left a) = encodeJson [fromString "Left", encodeJson a]
+  encodeJson (Right b) = encodeJson [fromString "Right", encodeJson b]
 
 instance encodeJsonUnit :: EncodeJson Unit where
   encodeJson = const jsonNull