Handle errors using custom types

Fixes #32.

src/Language/GraphQL/Execute.hs

@@ -1,10 +1,9 @@
 -- | This module provides functions to execute a @GraphQL@ request.
 module Language.GraphQL.Execute
     ( execute
-    , executeWithName
+    , module Language.GraphQL.Execute.Coerce
     ) where
 
-import qualified Data.Aeson as Aeson
 import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import Data.Sequence (Seq(..))
@@ -18,54 +17,38 @@ import qualified Language.GraphQL.Type.Definition as Definition
 import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.Type.Schema
 
--- | The substitution is applied to the document, and the resolvers are applied
--- to the resulting fields.
---
--- Returns the result of the query against the schema wrapped in a /data/
--- field, or errors wrapped in an /errors/ field.
-execute :: (Monad m, VariableValue a)
-    => Schema m -- ^ Resolvers.
-    -> HashMap.HashMap Name a -- ^ Variable substitution function.
-    -> Document -- @GraphQL@ document.
-    -> m Aeson.Value
-execute schema = executeRequest schema Nothing
-
 -- | The substitution is applied to the document, and the resolvers are applied
 -- to the resulting fields. The operation name can be used if the document
 -- defines multiple root operations.
 --
 -- Returns the result of the query against the schema wrapped in a /data/
 -- field, or errors wrapped in an /errors/ field.
-executeWithName :: (Monad m, VariableValue a)
-    => Schema m -- ^ Resolvers
-    -> Text -- ^ Operation name.
+execute :: (Monad m, VariableValue a, Serialize b)
+    => Schema m -- ^ Resolvers.
+    -> Maybe Text -- ^ Operation name.
     -> HashMap.HashMap Name a -- ^ Variable substitution function.
-    -> Document -- ^ @GraphQL@ Document.
-    -> m Aeson.Value
-executeWithName schema operationName =
-    executeRequest schema (Just operationName)
-
-executeRequest :: (Monad m, VariableValue a)
-    => Schema m
-    -> Maybe Text
-    -> HashMap.HashMap Name a
-    -> Document
-    -> m Aeson.Value
-executeRequest schema operationName subs document =
+    -> Document -- @GraphQL@ document.
+    -> m (Response b)
+execute schema operationName subs document =
     case Transform.document schema operationName subs document of
         Left queryError -> pure $ singleError $ Transform.queryError queryError
-        Right (Transform.Document types' rootObjectType operation)
-          | (Transform.Query _ fields) <- operation ->
-              executeOperation types' rootObjectType fields
-          | (Transform.Mutation _ fields) <- operation ->
-              executeOperation types' rootObjectType fields
+        Right transformed -> executeRequest transformed
+
+executeRequest :: (Monad m, Serialize a)
+    => Transform.Document m
+    -> m (Response a)
+executeRequest (Transform.Document types' rootObjectType operation)
+    | (Transform.Query _ fields) <- operation =
+        executeOperation types' rootObjectType fields
+    | (Transform.Mutation _ fields) <- operation =
+        executeOperation types' rootObjectType fields
 
 -- This is actually executeMutation, but we don't distinguish between queries
 -- and mutations yet.
-executeOperation :: Monad m
+executeOperation :: (Monad m, Serialize a)
     => HashMap Name (Type m)
     -> Out.ObjectType m
     -> Seq (Transform.Selection m)
-    -> m Aeson.Value
+    -> m (Response a)
 executeOperation types' objectType fields =
     runCollectErrs types' $ executeSelectionSet Definition.Null objectType fields