From 8da7427aa62ccb20bac98131ff7196b24474c2d1 Mon Sep 17 00:00:00 2001
From: Kalle Virtaneva <kallev@mercury.com>
Date: Thu, 31 Jul 2025 18:05:47 -0400
Subject: [PATCH 1/2] test: try to replicate issue with Maybe in tuple

---
 test/Basic.hs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/test/Basic.hs b/test/Basic.hs
index a6c7a86..ca4c6d2 100644
--- a/test/Basic.hs
+++ b/test/Basic.hs
@@ -20,6 +20,9 @@ $(deriveTypeScript (A.defaultOptions { A.tagSingleConstructors = True
 data Test1 = Test1 (Maybe Int)
 deriveTypeScript A.defaultOptions ''Test1
 
+data Test2 = Test2 String [Int] (Maybe String)
+deriveTypeScript A.defaultOptions ''Test2
+
 tests :: SpecWith ()
 tests = describe "Basic tests" $ do
   describe "tagSingleConstructors and constructorTagModifier" $ do
@@ -40,6 +43,12 @@ tests = describe "Basic tests" $ do
         , TSTypeAlternatives "ITest1" [] ["number | null"] Nothing
         ])
 
+    it [i|Maybe in multi-field tuple includes null option|] $ do
+      (getTypeScriptDeclarations (Proxy :: Proxy Test2)) `shouldBe` ([
+        TSTypeAlternatives "Test2" [] ["ITest2"] Nothing
+        , TSTypeAlternatives "ITest2" [] ["[string, number[], string | null]"] Nothing
+        ])
+
 
 main :: IO ()
 main = hspec tests

From 808896ed6ed3600fa8ffed470110791e74a53998 Mon Sep 17 00:00:00 2001
From: Kalle Virtaneva <kallev@mercury.com>
Date: Thu, 31 Jul 2025 18:20:37 -0400
Subject: [PATCH 2/2] feat: try to get test to pass

---
 src/Data/Aeson/TypeScript/TH.hs | 17 +++++++++++++----
 test/Basic.hs                   | 22 ++++++++++++++++++++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/src/Data/Aeson/TypeScript/TH.hs b/src/Data/Aeson/TypeScript/TH.hs
index 3cd7227..3ce3491 100644
--- a/src/Data/Aeson/TypeScript/TH.hs
+++ b/src/Data/Aeson/TypeScript/TH.hs
@@ -308,10 +308,19 @@ handleConstructor (ExtraTypeScriptOptions {..}) options (DatatypeInfo {..}) gene
     interfaceName = "I" <> (lastNameComponent' $ constructorName ci)
 
     tupleEncoding = do
-      let typ = contentsTupleTypeSubstituted genericVariables ci
-      stringExp <- lift $ case typ of
-        (AppT (ConT name) t) | name == ''Maybe -> [|$(getTypeAsStringExp t) <> " | null"|]
-        _ -> getTypeAsStringExp typ
+      let fields = constructorFields ci
+      stringExp <- lift $ case fields of
+        [] -> [|"void[]"|]
+        [x] -> case mapType genericVariables x of
+          (AppT (ConT name) t) | name == ''Maybe -> [|$(getTypeAsStringExp t) <> " | null"|]
+          mappedType -> getTypeAsStringExp mappedType
+        xs -> do
+          -- Process each field individually to handle Maybe types
+          fieldStrings <- forM (fmap (mapType genericVariables) xs) $ \fieldType -> case fieldType of
+            (AppT (ConT name) t) | name == ''Maybe -> [|$(getTypeAsStringExp t) <> " | null"|]
+            _ -> getTypeAsStringExp fieldType
+          let fieldExps = map return fieldStrings
+          [|"[" <> $(foldr1 (\a b -> [|$a <> ", " <> $b|]) fieldExps) <> "]"|]
 
       lift [|TSTypeAlternatives $(TH.stringE interfaceName)
                                 $(genericVariablesListExpr True genericVariables)
diff --git a/test/Basic.hs b/test/Basic.hs
index ca4c6d2..72a72c2 100644
--- a/test/Basic.hs
+++ b/test/Basic.hs
@@ -4,6 +4,7 @@ module Basic (tests) where
 import Data.Aeson as A
 import Data.Aeson.TypeScript.TH
 import Data.Aeson.TypeScript.Types
+import Data.List.NonEmpty (NonEmpty)
 import Data.Proxy
 import Data.String.Interpolate
 import Prelude hiding (Double)
@@ -23,6 +24,21 @@ deriveTypeScript A.defaultOptions ''Test1
 data Test2 = Test2 String [Int] (Maybe String)
 deriveTypeScript A.defaultOptions ''Test2
 
+-- Test case for Maybe types in multi-field tuples
+data PromptKey = PromptKey String deriving (Eq, Show)
+
+$(deriveTypeScript A.defaultOptions ''PromptKey)
+
+newtype ExtraInputPrompt = ExtraInputPrompt String deriving (Eq, Show)
+
+$(deriveTypeScript A.defaultOptions ''ExtraInputPrompt)
+
+data WidgetActionPayload
+  = InfoRequest String [PromptKey] (Maybe (NonEmpty ExtraInputPrompt))
+  deriving (Eq, Show)
+
+$(deriveTypeScript A.defaultOptions ''WidgetActionPayload)
+
 tests :: SpecWith ()
 tests = describe "Basic tests" $ do
   describe "tagSingleConstructors and constructorTagModifier" $ do
@@ -49,6 +65,12 @@ tests = describe "Basic tests" $ do
         , TSTypeAlternatives "ITest2" [] ["[string, number[], string | null]"] Nothing
         ])
 
+    it [i|WidgetActionPayload tuple includes null for Maybe list|] $ do
+      (getTypeScriptDeclarations (Proxy :: Proxy WidgetActionPayload))
+        `shouldBe` ( [ TSTypeAlternatives "WidgetActionPayload" [] ["IInfoRequest"] Nothing,
+                       TSTypeAlternatives "IInfoRequest" [] ["[string, PromptKey[], ExtraInputPrompt[] | null]"] Nothing
+                     ]
+                   )
 
 main :: IO ()
 main = hspec tests