Support subscriptions

This is experimental support.
The implementation is based on conduit and is boring. There is a new
resolver data constructor that should create a source event stream. The
executor receives the events, pipes them through the normal execution
and puts them into the response stream which is returned to the user.

- Tests are missing.
- The executor should check field value resolver on subscription types.
- The graphql function should probably return (Either
  ResponseEventStream Response), but I'm not sure about this. It will
  make the usage more complicated if no subscriptions are involved, but
  with the current API implementing subscriptions is more
  difficult than it should be.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/Language/GraphQL/Type.hs b/src/Language/GraphQL/Type.hs
index 0a30924..e84fc03 100644
--- a/src/Language/GraphQL/Type.hs
+++ b/src/Language/GraphQL/Type.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/. -}
+
 -- | Reexports non-conflicting type system and schema definitions.
 module Language.GraphQL.Type
     ( In.InputField(..)
@@ -6,7 +10,10 @@ module Language.GraphQL.Type
     , Out.Field(..)
     , Out.InterfaceType(..)
     , Out.ObjectType(..)
-    , Out.ResolverT(..)
+    , Out.Resolve
+    , Out.Resolver(..)
+    , Out.SourceEventStream
+    , Out.Subscribe
     , Out.UnionType(..)
     , Out.argument
     , module Language.GraphQL.Type.Definition