Allow schema to be specified as {mod, fun}

This fixes an “invalid quoted expression” issue with macro expansion when using this syntax:

    get “/“, Plug, schema: Schema.schema

but we can use:

	get “/“, Plug, schema: {Schema, :schema}

Author: Josh Price

lib/graphql/plug/endpoint.ex

@@ -5,12 +5,15 @@ defmodule GraphQL.Plug.Endpoint do
   @behaviour Plug
 
   def init(opts) do
-    opts
+    schema = case Keyword.get(opts, :schema) do
+      {mod, func} -> apply(mod, func, [])
+      s -> s
+    end
+    %{schema: schema}
   end
 
-  def call(%Conn{method: req_method, params: %{"query" => query}} = conn, opts)
+  def call(%Conn{method: req_method, params: %{"query" => query}} = conn, %{schema: schema})
   when req_method in ["GET", "POST"] do
-    schema = opts[:schema]
     cond do
       query && String.strip(query) != "" -> handle_call(conn, schema, query)
       true -> handle_error(conn, "Must provide query string.")

test/graphql/plug/endpoint_test.exs

@@ -22,7 +22,6 @@ defmodule GraphQL.Plug.EndpointTest do
     def greeting(_, _, _), do: greeting(%{}, %{name: "world"}, %{})
   end
 
-  # Setup a Plug which calls the Plug under test
   defmodule TestPlug do
     use Plug.Builder
 
@@ -39,7 +38,6 @@ defmodule GraphQL.Plug.EndpointTest do
     assert conn.status == status
     assert get_resp_header(conn, "content-type") == ["application/json; charset=utf-8"]
     assert conn.resp_body == body
-    # assert conn.halted == true
   end
 
   test "GET and POST successful query" do
@@ -48,6 +46,20 @@ defmodule GraphQL.Plug.EndpointTest do
     assert_query {:post, "/", query: "{greeting}"}, {200, success}
   end
 
+  test "specify schema using {module, fun} syntax" do
+    defmodule TestMFPlug do
+      use Plug.Builder
+
+      plug GraphQL.Plug.Endpoint, schema: {TestSchema, :schema}
+    end
+    conn = conn(:get, "/", query: "{greeting}")
+    conn = TestMFPlug.call conn, []
+
+    assert conn.status == 200
+    assert get_resp_header(conn, "content-type") == ["application/json; charset=utf-8"]
+    assert conn.resp_body == ~S({"data":{"greeting":"Hello, world!"}})
+  end
+
   test "missing query" do
     no_query_found_error = ~S({"errors":[{"message":"Must provide query string."}]})
     assert_query {:get,  "/", nil},         {400, no_query_found_error}