Introduce `graphql` function

This simplifies Attoparsec parsing when executing a GraphQL
query.

Data/GraphQL.hs

@@ -0,0 +1,16 @@
+module Data.GraphQL where
+
+import Control.Applicative (Alternative, empty)
+
+import Data.Text (Text)
+
+import qualified Data.Aeson as Aeson
+import qualified Data.Attoparsec.Text as Attoparsec
+
+import Data.GraphQL.Execute
+import Data.GraphQL.Parser
+import Data.GraphQL.Schema
+
+graphql :: (Alternative m, Monad m) => Schema m -> Text -> m Aeson.Value
+graphql schema = either (const empty) (execute schema)
+               . Attoparsec.parseOnly document

graphql.cabal

@@ -22,7 +22,8 @@ data-files:          tests/data/*.graphql
 library
   default-language:    Haskell2010
   ghc-options:         -Wall
-  exposed-modules:     Data.GraphQL.AST
+  exposed-modules:     Data.GraphQL
+                       Data.GraphQL.AST
                        Data.GraphQL.Encoder
                        Data.GraphQL.Execute
                        Data.GraphQL.Schema

tests/Test/StarWars.hs

@@ -11,30 +11,23 @@ import Control.Applicative (Alternative, (<|>), empty, liftA2)
 import Data.Maybe (catMaybes)
 
 import qualified Data.Aeson as Aeson
-import Data.Attoparsec.Text (parseOnly)
 import Data.Text (Text)
 
-import Test.Tasty (TestTree)
-import Test.Tasty.HUnit
+import Test.Tasty (TestTree, testGroup)
+import Test.Tasty.HUnit (testCase, (@?=))
 
-import Data.GraphQL.AST
-import Data.GraphQL.Execute
-import qualified Data.GraphQL.Parser as Parser
+import Data.GraphQL
 import Data.GraphQL.Schema
 
-
 -- * Test
 -- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsQueryTests.js
 
 test :: TestTree
-test = testCase "R2-D2" $ execute schema heroQuery @?= expected
-  where
-    heroQuery :: Document
-    heroQuery = either (error "Parsing error") id $ parseOnly Parser.document
-      "query HeroNameQuery{hero{name}}"
-
-    expected :: Maybe Response
-    expected = Just $ Aeson.Object [("hero", Aeson.Object [("name", "R2-D2")])]
+test = testGroup "Basic Queries"
+     [testCase "R2-D2"
+         $  graphql schema "query HeroNameQuery{hero{name}}"
+        @?= Just (Aeson.Object [("hero", Aeson.Object [("name", "R2-D2")])])
+     ]
 
 -- * Schema
 -- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsSchema.js