Handle Maybe correctly in tuple encodings (fixes #49)

Author: thomasjm

src/Data/Aeson/TypeScript/TH.hs

@@ -307,10 +307,15 @@ handleConstructor (ExtraTypeScriptOptions {..}) options (DatatypeInfo {..}) gene
     -- * Type declaration to use
     interfaceName = "I" <> (lastNameComponent' $ constructorName ci)
 
-    tupleEncoding =
+    tupleEncoding = do
+      let typ = contentsTupleTypeSubstituted genericVariables ci
+      stringExp <- lift $ case typ of
+        (AppT (ConT name) t) | name == ''Maybe -> [|$(getTypeAsStringExp t) <> " | null"|]
+        _ -> getTypeAsStringExp typ
+
       lift [|TSTypeAlternatives $(TH.stringE interfaceName)
                                 $(genericVariablesListExpr True genericVariables)
-                                [getTypeScriptType (Proxy :: Proxy $(return (contentsTupleTypeSubstituted genericVariables ci)))]
+                                [$(return stringExp)]
                                 $(tryGetDoc haddockModifier (constructorName ci))|]
 
     assembleInterfaceDeclaration members = [|TSInterfaceDeclaration $(TH.stringE interfaceName)

test/Basic.hs

@@ -17,6 +17,9 @@ data Unit2 = Unit2
 $(deriveTypeScript (A.defaultOptions { A.tagSingleConstructors = True
                                      , A.constructorTagModifier = const "foo" }) ''Unit2)
 
+data Test1 = Test1 (Maybe Int)
+deriveTypeScript A.defaultOptions ''Test1
+
 tests :: SpecWith ()
 tests = describe "Basic tests" $ do
   describe "tagSingleConstructors and constructorTagModifier" $ do
@@ -31,6 +34,12 @@ tests = describe "Basic tests" $ do
         TSTypeAlternatives "Unit2" [] ["\"foo\""] Nothing
         ])
 
+    it [i|Maybe tuple encoding includes null option|] $ do
+      (getTypeScriptDeclarations (Proxy :: Proxy Test1)) `shouldBe` ([
+        TSTypeAlternatives "Test1" [] ["ITest1"] Nothing
+        , TSTypeAlternatives "ITest1" [] ["number | null"] Nothing
+        ])
+
 
 main :: IO ()
 main = hspec tests