Use prefixItems for tuples

src/Data/OpenApi.hs

@@ -75,6 +75,7 @@ module Data.OpenApi (
   Schema(..),
   NamedSchema(..),
   OpenApiItems(..),
+  OpenApiPrefixItems(..),
   Xml(..),
   Pattern,
   AdditionalProperties(..),

src/Data/OpenApi/Internal.hs

@@ -603,6 +603,10 @@ data OpenApiItems where
   OpenApiItemsArray     :: [Referenced Schema] -> OpenApiItems
   deriving (Eq, Show, Typeable, Data)
 
+data OpenApiPrefixItems where
+  OpenApiPrefixItemsArray :: [Referenced Schema] -> OpenApiPrefixItems
+  deriving (Eq, Show, Typeable, Data)
+
 data OpenApiType where
   OpenApiString   :: OpenApiType
   OpenApiNumber   :: OpenApiType
@@ -665,6 +669,7 @@ data Schema = Schema
   , _schemaType :: Maybe OpenApiType
   , _schemaFormat :: Maybe Format
   , _schemaItems :: Maybe OpenApiItems
+  , _schemaPrefixItems :: Maybe OpenApiPrefixItems
   , _schemaMaximum :: Maybe Scientific
   , _schemaExclusiveMaximum :: Maybe Bool
   , _schemaMinimum :: Maybe Scientific
@@ -1375,6 +1380,14 @@ instance ToJSON OpenApiItems where
     ]
   toJSON (OpenApiItemsArray  x) = object [ "items" .= x ]
 
+instance ToJSON OpenApiPrefixItems where
+  toJSON (OpenApiPrefixItemsArray []) = object
+    [ "prefixItems" .= object []
+    , "maxItems" .= (0 :: Int)
+    , "example" .= Array mempty
+    ]
+  toJSON (OpenApiPrefixItemsArray x) = object [ "prefixItems" .= x ]
+
 instance ToJSON Components where
   toJSON = sopSwaggerGenericToJSON
   toEncoding = sopSwaggerGenericToEncoding
@@ -1530,6 +1543,10 @@ instance FromJSON OpenApiItems where
   parseJSON js@(Array _)  = OpenApiItemsArray  <$> parseJSON js
   parseJSON _ = empty
 
+instance FromJSON OpenApiPrefixItems where
+  parseJSON js@(Array _) = OpenApiPrefixItemsArray <$> parseJSON js
+  parseJSON _ = empty
+
 instance FromJSON Components where
   parseJSON = sopSwaggerGenericParseJSON
 

src/Data/OpenApi/Internal/Schema.hs

@@ -346,7 +346,7 @@ inlineNonRecursiveSchemas defs = inlineSchemasWhen nonRecursive defs
 --         2,
 --         3
 --     ],
---     "items": {
+--     "prefixItems": {
 --         "type": "number"
 --     },
 --     "type": "array"
@@ -358,7 +358,7 @@ inlineNonRecursiveSchemas defs = inlineSchemasWhen nonRecursive defs
 --         "Jack",
 --         25
 --     ],
---     "items": [
+--     "prefixItems": [
 --         {
 --             "type": "string"
 --         },
@@ -407,6 +407,7 @@ sketchSchema = sketch . toJSON
       & items ?~ case ischema of
           Just s -> OpenApiItemsObject (Inline s)
           _      -> OpenApiItemsArray (map Inline ys)
+      & prefixItems ?~ OpenApiPrefixItemsArray (map Inline ys)
       where
         ys = map go (V.toList xs)
         allSame = and ((zipWith (==)) ys (tail ys))
@@ -573,6 +574,7 @@ sketchStrictSchema = go . toJSON
       & maxItems    ?~ fromIntegral sz
       & minItems    ?~ fromIntegral sz
       & items       ?~ OpenApiItemsArray (map (Inline . go) (V.toList xs))
+      & prefixItems ?~ OpenApiPrefixItemsArray (map (Inline . go) (V.toList xs))
       & uniqueItems ?~ allUnique
       & enum_       ?~ [js]
       where
@@ -992,6 +994,10 @@ appendItem x Nothing = Just (OpenApiItemsArray [x])
 appendItem x (Just (OpenApiItemsArray xs)) = Just (OpenApiItemsArray (xs ++ [x]))
 appendItem _ _ = error "GToSchema.appendItem: cannot append to OpenApiItemsObject"
 
+appendPrefixItem :: Referenced Schema -> Maybe OpenApiPrefixItems -> Maybe OpenApiPrefixItems
+appendPrefixItem x Nothing = Just (OpenApiPrefixItemsArray [x])
+appendPrefixItem x (Just (OpenApiPrefixItemsArray xs)) = Just (OpenApiPrefixItemsArray (xs ++ [x]))
+
 withFieldSchema :: forall proxy s f. (Selector s, GToSchema f) =>
   SchemaOptions -> proxy s f -> Bool -> Schema -> Declare (Definitions Schema) Schema
 withFieldSchema opts _ isRequiredField schema = do

src/Data/OpenApi/Lens.hs

@@ -115,6 +115,12 @@ instance
   => HasItems s (Maybe OpenApiItems) where
   items = schema.items
 
+instance
+  {-# OVERLAPPABLE #-}
+  HasSchema s Schema
+  => HasPrefixItems s (Maybe OpenApiPrefixItems) where
+  prefixItems = schema.prefixItems
+
 instance
   {-# OVERLAPPABLE #-}
   HasSchema s Schema

src/Data/OpenApi/Optics.hs

@@ -176,6 +176,20 @@ instance
   labelOptic = unto (\x -> OpenApiItemsObject x)
   {-# INLINE labelOptic #-}
 
+-- OpenApiPrefixItems prisms
+
+instance
+  ( a ~ [Referenced Schema]
+  , b ~ [Referenced Schema]
+  ) => LabelOptic "_OpenApiPrefixItemsArray"
+         A_Review
+         OpenApiPrefixItems
+         OpenApiPrefixItems
+         a
+         b where
+  labelOptic = unto (\x -> OpenApiPrefixItemsArray x)
+  {-# INLINE labelOptic #-}
+
 -- =============================================================
 -- More helpful instances for easier access to schema properties
 
@@ -232,6 +246,15 @@ instance
   ) => LabelOptic "items" A_Lens NamedSchema NamedSchema a b where
   labelOptic = #schema % #items
   {-# INLINE labelOptic #-}
+
+-- #prefixItems
+
+instance
+  ( a ~ Maybe OpenApiPrefixItems
+  , b ~ Maybe OpenApiPrefixItems
+  ) => LabelOptic "prefixItems" A_Lens NamedSchema NamedSchema a b where
+  labelOptic = #schema % #prefixItems
+  {-# INLINE labelOptic #-}
 
 -- #maximum
 

src/Data/OpenApi/Schema/Generator.hs

@@ -72,6 +72,11 @@ schemaGen defns schema =
               OpenApiItemsArray refs ->
                   let itemGens = schemaGen defns . dereference defns <$> refs
                   in fmap (Array . V.fromList) $ sequence itemGens
+        | Just prefixItems <- schema ^. prefixItems -> do
+            case prefixItems of
+              OpenApiPrefixItemsArray refs ->
+                let itemGens = schemaGen defns . dereference defns <$> refs
+                in fmap (Array . V.fromList) $ sequence itemGens
       Just OpenApiString -> do
         size <- getSize
         let minLength' = fromMaybe 0 $ fromInteger <$> schema ^. minLength

test/Data/OpenApi/CommonTestTypes.hs

@@ -482,7 +482,7 @@ ispairSchemaJSON :: Value
 ispairSchemaJSON = [aesonQQ|
 {
   "type": "array",
-  "items":
+  "prefixItems":
     [
       { "type": "integer" },
       { "type": "string"  }