Respect subscriptions in the executor

After the last commit there were a few places needed to be adjusted to
support subscriptions. This is done and a test case is added.

It is important to implement subscriptions now, because they require
changes to the library API, and they are a big missing part to finish
the executor. When the executor is finished, we can start to provide
more stable API without breaking everything every release. Validation
and introspection shouldn't require much changes to the API; AST would
require some changes to report good errors after the validation - this
is one thing I can think of.

Fixes #5.

tests/Test/DirectiveSpec.hs

@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 module Test.DirectiveSpec
@@ -14,7 +18,8 @@ import Test.Hspec (Spec, describe, it, shouldBe)
 import Text.RawString.QQ (r)
 
 experimentalResolver :: Schema IO
-experimentalResolver = Schema { query = queryType, mutation = Nothing }
+experimentalResolver = Schema
+    { query = queryType, mutation = Nothing, subscription = Nothing }
   where
     queryType = Out.ObjectType "Query" Nothing []
         $ HashMap.singleton "experimentalField"

tests/Test/FragmentSpec.hs

@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 module Test.FragmentSpec
@@ -76,7 +80,7 @@ sizeFieldType
 
 toSchema :: Text -> (Text, Value) -> Schema IO
 toSchema t (_, resolve) = Schema
-    { query = queryType, mutation = Nothing }
+    { query = queryType, mutation = Nothing, subscription = Nothing }
   where
     unionMember = if t == "Hat" then hatType else shirtType
     typeNameField = Out.Field Nothing (Out.NamedScalarType string) mempty

tests/Test/RootOperationSpec.hs

@@ -1,3 +1,7 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
 module Test.RootOperationSpec
@@ -20,8 +24,10 @@ hatType = Out.ObjectType "Hat" Nothing []
 
 schema :: Schema IO
 schema = Schema
-    (Out.ObjectType "Query" Nothing [] hatFieldResolver)
-    (Just $ Out.ObjectType "Mutation" Nothing [] incrementFieldResolver)
+    { query = Out.ObjectType "Query" Nothing [] hatFieldResolver
+    , mutation = Just $ Out.ObjectType "Mutation" Nothing [] incrementFieldResolver
+    , subscription = Nothing
+    }
   where
     garment = pure $ Object $ HashMap.fromList
         [ ("circumference", Int 60)

tests/Test/StarWars/Schema.hs

@@ -20,7 +20,11 @@ import Prelude hiding (id)
 -- See https://github.com/graphql/graphql-js/blob/master/src/__tests__/starWarsSchema.js
 
 schema :: Schema Identity
-schema = Schema { query = queryType, mutation = Nothing }
+schema = Schema
+    { query = queryType
+    , mutation = Nothing
+    , subscription = Nothing
+    }
   where
     queryType = Out.ObjectType "Query" Nothing [] $ HashMap.fromList
         [ ("hero", heroFieldResolver)