Fix compatibility with GraphQL Interpreter and BatchLoader.for

lib/batch_loader/graphql.rb

@@ -4,30 +4,44 @@ class BatchLoader
   class GraphQL
     def self.use(schema_definition)
       schema_definition.lazy_resolve(BatchLoader::GraphQL, :sync)
-      # for graphql gem versions <= 1.8.6 which work with BatchLoader instead of BatchLoader::GraphQL
-      schema_definition.instrument(:field, self)
+
+      # in cases when BatchLoader is being used instead of BatchLoader::GraphQL
+      if schema_definition.respond_to?(:interpreter?) && schema_definition.interpreter?
+        schema_definition.tracer(self)
+      else
+        schema_definition.instrument(:field, self)
+      end
+    end
+
+    def self.trace(event, _data)
+      if event == 'execute_field'
+        result = yield
+        result.respond_to?(:__sync) ? wrap(result) : result
+      else
+        yield
+      end
     end
 
     def self.instrument(type, field)
       old_resolve_proc = field.resolve_proc
       new_resolve_proc = ->(object, arguments, context) do
         result = old_resolve_proc.call(object, arguments, context)
-        result.respond_to?(:__sync) ? BatchLoader::GraphQL.wrap(result) : result
+        result.respond_to?(:__sync) ? wrap(result) : result
       end
 
       field.redefine { resolve(new_resolve_proc) }
     end
 
+    def self.for(item)
+      new(item)
+    end
+
     def self.wrap(batch_loader)
       BatchLoader::GraphQL.new.tap do |graphql|
         graphql.batch_loader = batch_loader
       end
     end
 
-    def self.for(item)
-      new(item)
-    end
-
     attr_writer :batch_loader
 
     def initialize(item = nil)

spec/fixtures/graphql_schema.rb

@@ -64,4 +64,13 @@ class GraphqlSchema < GraphQL::Schema
     query QueryType
     use BatchLoader::GraphQL
   end
+
+  if defined?(GraphQL::Execution::Interpreter)
+    class GraphqlSchemaWithInterpreter < GraphQL::Schema
+      use GraphQL::Execution::Interpreter
+      use GraphQL::Analysis::AST
+      query QueryType
+      use BatchLoader::GraphQL
+    end
+  end
 end

spec/graphql_spec.rb

@@ -1,7 +1,22 @@
 require "spec_helper"
 
 RSpec.describe 'GraphQL integration' do
+  after do
+    User.destroy_all
+    Post.destroy_all
+  end
+
   it 'resolves BatchLoader fields lazily' do
+    test(GraphqlSchema)
+  end
+
+  if defined?(GraphqlSchemaWithInterpreter)
+    it 'resolves BatchLoader fields lazily with GraphQL Interpreter' do
+      test(GraphqlSchemaWithInterpreter)
+    end
+  end
+
+  def test(schema)
     user1 = User.save(id: "1")
     user2 = User.save(id: "2")
     Post.save(user_id: user1.id)
@@ -17,7 +32,7 @@
 
     expect(User).to receive(:where).with(id: ["1", "2"]).twice.and_call_original
 
-    result = GraphqlSchema.execute(query)
+    result = schema.execute(query)
 
     expect(result['data']).to eq({
       'posts' => [