Merge pull request #22 from justinwoo/nullorundefined-instances

add decode/encode instances for NullOrUndefined

src/Data/Foreign/Class.purs

@@ -5,6 +5,8 @@ import Control.Monad.Except (mapExcept)
 import Data.Array ((..), zipWith, length)
 import Data.Bifunctor (lmap)
 import Data.Foreign (F, Foreign, ForeignError(ErrorAtIndex), readArray, readBoolean, readChar, readInt, readNumber, readString, toForeign)
+import Data.Foreign.NullOrUndefined (NullOrUndefined(..), readNullOrUndefined, undefined)
+import Data.Maybe (maybe)
 import Data.Traversable (sequence)
 
 -- | The `Decode` class is used to generate decoding functions
@@ -89,3 +91,9 @@ instance intEncode :: Encode Int where
 
 instance arrayEncode :: Encode a => Encode (Array a) where
   encode = toForeign <<< map encode
+
+instance decodeNullOrUndefined :: Decode a => Decode (NullOrUndefined a) where
+  decode = readNullOrUndefined decode
+
+instance encodeNullOrUndefined :: Encode a => Encode (NullOrUndefined a) where
+  encode (NullOrUndefined a) = maybe undefined encode a

src/Data/Foreign/NullOrUndefined.js

@@ -0,0 +1 @@
+exports['undefined'] = undefined;

src/Data/Foreign/NullOrUndefined.purs

@@ -28,3 +28,5 @@ unNullOrUndefined (NullOrUndefined m) = m
 readNullOrUndefined :: forall a. (Foreign -> F a) -> Foreign -> F (NullOrUndefined a)
 readNullOrUndefined _ value | isNull value || isUndefined value = pure (NullOrUndefined Nothing)
 readNullOrUndefined f value = NullOrUndefined <<< Just <$> f value
+
+foreign import undefined :: Foreign

test/Main.purs

@@ -8,9 +8,11 @@ import Data.Bifunctor (bimap)
 import Data.Either (Either(..))
 import Data.Foreign.Class (class Encode, class Decode)
 import Data.Foreign.Generic (decodeJSON, encodeJSON)
+import Data.Foreign.NullOrUndefined (NullOrUndefined(..))
+import Data.Maybe (Maybe(..))
 import Data.Tuple (Tuple(..))
 import Test.Assert (assert, assert', ASSERT)
-import Test.Types (IntList(..), RecordTest(..), Tree(..), TupleArray(..))
+import Test.Types (IntList(..), RecordTest(..), Tree(..), TupleArray(..), UndefinedTest(..))
 
 buildTree :: forall a. (a -> TupleArray a a) -> Int -> a -> Tree a
 buildTree _ 0 a = Leaf a
@@ -44,5 +46,9 @@ main :: forall eff. Eff (console :: CONSOLE, assert :: ASSERT | eff) Unit
 main = do
   testRoundTrip (RecordTest { foo: 1, bar: "test", baz: 'a' })
   testRoundTrip (Cons 1 (Cons 2 (Cons 3 Nil)))
+  testRoundTrip (UndefinedTest {a: NullOrUndefined (Just "test")})
+  testRoundTrip (UndefinedTest {a: NullOrUndefined Nothing})
+  testRoundTrip [NullOrUndefined (Just "test")]
+  testRoundTrip [NullOrUndefined (Nothing :: Maybe String)]
   testRoundTrip (makeTree 0)
   testRoundTrip (makeTree 5)

test/Types.purs

@@ -5,6 +5,7 @@ import Data.Bifunctor (class Bifunctor)
 import Data.Foreign (ForeignError(ForeignError), fail, readArray, toForeign)
 import Data.Foreign.Class (class Encode, class Decode, encode, decode)
 import Data.Foreign.Generic (defaultOptions, genericDecode, genericEncode)
+import Data.Foreign.NullOrUndefined (NullOrUndefined)
 import Data.Generic.Rep (class Generic)
 import Data.Generic.Rep.Eq (genericEq)
 import Data.Generic.Rep.Show (genericShow)
@@ -86,3 +87,15 @@ instance decodeTree :: Decode a => Decode (Tree a) where
 
 instance encodeTree :: Encode a => Encode (Tree a) where
   encode x = genericEncode defaultOptions x
+
+newtype UndefinedTest = UndefinedTest
+  { a :: NullOrUndefined String
+  }
+
+derive instance eqUT :: Eq UndefinedTest
+derive instance geUT :: Generic UndefinedTest _
+
+instance dUT :: Decode UndefinedTest where
+  decode = genericDecode $ defaultOptions
+instance eUT :: Encode UndefinedTest where
+  encode = genericEncode $ defaultOptions