Merge pull request #161 from haskell-graphql/move-defaultable

Move Defaultable into GraphQL.API

Author: jml

CHANGELOG.rst

@@ -9,15 +9,17 @@ Breaking changes
 ----------------
 
 * ``Enum`` handlers are now monadic (see `#118`_)
-* restrict usage to Protolude 0.2.1 and later
+* You must use protolude 0.2.1 or later
+* ``Defaultable`` must now be imported from ``GraphQL.API``, rather than ``GraphQL.Resolver``,
+  this moves ``GraphQL.API`` closer to being sufficient for API definition. (see `#149`_)
 
 Improvements
 ------------
 
 * Now support GHC 8.2 as well as 8.0.2 and later
 
 .. _`#118`: https://github.com/jml/graphql-api/issues/118
-
+.. _`#149`: https://github.com/haskell-graphql/graphql-api/issues/149
 
 v0.2.0 (2017-10-12)
 ===================

src/GraphQL/API.hs

@@ -15,13 +15,13 @@ module GraphQL.API
   ( Object
   , Field
   , Argument
-  , DefaultArgument
   , Union
   , List
   , Enum
   , GraphQLEnum(..)
   , Interface
   , (:>)(..)
+  , Defaultable(..)
   , HasAnnotatedType(..)
   , HasAnnotatedInputType
   , HasObjectDefinition(..)
@@ -36,7 +36,7 @@ import Protolude hiding (Enum, TypeError)
 
 import GHC.TypeLits (Symbol, KnownSymbol, TypeError, ErrorMessage(..))
 import qualified GraphQL.Internal.Schema as Schema
-import GraphQL.Internal.Name (NameError, nameFromSymbol)
+import GraphQL.Internal.Name (Name, NameError, nameFromSymbol)
 import GraphQL.API.Enum (GraphQLEnum(..))
 import GHC.Generics ((:*:)(..))
 import GHC.Types (Type)
@@ -82,11 +82,34 @@ data Field (name :: Symbol) (fieldType :: Type)
 data Argument (name :: Symbol) (argType :: Type)
 
 
--- Can't set the value for default arguments via types, but can
--- distinguish to force users to provide a default argument somewhere
--- in their function (using Maybe? ore some new type like
--- https://hackage.haskell.org/package/optional-args-1.0.1)
-data DefaultArgument (name :: Symbol) (argType :: Type)
+-- | Specify a default value for a type in a GraphQL schema.
+--
+-- GraphQL schema can have default values in certain places. For example,
+-- arguments to fields can have default values. Because we cannot lift
+-- arbitrary values to the type level, we need some way of getting at those
+-- values. This typeclass provides the means.
+--
+-- To specify a default, implement this typeclass.
+--
+-- The default implementation is to say that there *is* no default for this
+-- type.
+class Defaultable a where
+  -- | defaultFor returns the value to be used when no value has been given.
+  defaultFor :: Name -> Maybe a
+  defaultFor _ = empty
+
+instance Defaultable Int32
+
+instance Defaultable Double
+
+instance Defaultable Bool
+
+instance Defaultable Text
+
+instance Defaultable (Maybe a) where
+  -- | The default for @Maybe a@ is @Nothing@.
+  defaultFor _ = pure Nothing
+
 
 cons :: a -> [a] -> [a]
 cons = (:)
@@ -316,7 +339,7 @@ instance forall dataName consName records s l p.
           . Schema.NonNullTypeNamed
           . Schema.DefinedInputType
           . Schema.InputTypeDefinitionObject
-          . (Schema.InputObjectTypeDefinition name)
+          . Schema.InputObjectTypeDefinition name
           . Schema.NonEmptyList
         ) (genericGetInputObjectFieldDefinitions @records)
 

src/GraphQL/Resolver.hs

@@ -17,7 +17,6 @@ module GraphQL.Resolver
   ( ResolverError(..)
   , HasResolver(..)
   , (:<>)(..)
-  , Defaultable(..)
   , Result(..)
   , unionValue
   ) where
@@ -146,38 +145,10 @@ class HasResolver m a where
   type Handler m a
   resolve :: Handler m a -> Maybe (SelectionSetByType Value) -> m (Result Value)
 
--- | Specify a default value for a type in a GraphQL schema.
---
--- GraphQL schema can have default values in certain places. For example,
--- arguments to fields can have default values. Because we cannot lift
--- arbitrary values to the type level, we need some way of getting at those
--- values. This typeclass provides the means.
---
--- To specify a default, implement this typeclass.
---
--- The default implementation is to say that there *is* no default for this
--- type.
-class Defaultable a where
-  -- | defaultFor returns the value to be used when no value has been given.
-  defaultFor :: Name -> Maybe a
-  defaultFor _ = empty
-
 -- | Called when the schema expects an input argument @name@ of type @a@ but
 -- @name@ has not been provided.
-valueMissing :: Defaultable a => Name -> Either ResolverError a
-valueMissing name = maybe (Left (ValueMissing name)) Right (defaultFor name)
-
-instance Defaultable Int32
-
-instance Defaultable Double
-
-instance Defaultable Bool
-
-instance Defaultable Text
-
-instance Defaultable (Maybe a) where
-  -- | The default for @Maybe a@ is @Nothing@.
-  defaultFor _ = pure Nothing
+valueMissing :: API.Defaultable a => Name -> Either ResolverError a
+valueMissing name = maybe (Left (ValueMissing name)) Right (API.defaultFor name)
 
 instance forall m. (Applicative m) => HasResolver m Int32 where
   type Handler m Int32 = m Int32
@@ -287,7 +258,7 @@ instance forall ksH t f m.
   ( KnownSymbol ksH
   , BuildFieldResolver m f
   , FromValue t
-  , Defaultable t
+  , API.Defaultable t
   , HasAnnotatedInputType t
   , Monad m
   ) => BuildFieldResolver m (PlainArgument (API.Argument ksH t) f) where
@@ -303,7 +274,7 @@ instance forall ksK t f m name.
   ( KnownSymbol ksK
   , BuildFieldResolver m f
   , KnownSymbol name
-  , Defaultable t
+  , API.Defaultable t
   , API.GraphQLEnum t
   , Monad m
   ) => BuildFieldResolver m (EnumArgument (API.Argument ksK (API.Enum name t)) f) where

tests/ExampleSchema.hs

@@ -85,10 +85,8 @@ import GraphQL.API
   , Interface
   , Union
   , (:>)
+  , Defaultable(..)
   )
--- XXX: This really shouldn't be part of Resolver, since whether or not a
--- thing has a default is part of the API / Schema definition.
-import GraphQL.Resolver (Defaultable(..))
 import GraphQL.Value (pattern ValueEnum, unName)
 import GraphQL.Value.ToValue (ToValue(..))
 

tests/Examples/InputObject.hs

@@ -7,7 +7,7 @@ import Protolude hiding (Enum)
 
 import GraphQL
 import GraphQL.API
-import GraphQL.Resolver (Handler, Defaultable(..))
+import GraphQL.Resolver (Handler)
 import GraphQL.Value.FromValue (FromValue)
 
 data DogStuff = DogStuff { toy :: Text, likesTreats :: Bool } deriving (Show, Generic)