Investigate why #1686 was such a big performance boot, that there are dup'ed relationships being yielded

[bf4]

See #1686 (comment)

if serializer.associations(@include_tree).each yields an association multiple times, it means self.class._reflections.each (here) yields them several times.

[beauby]

As mentionned on slack, I couldn't get dupes there.

[bf4]

bundle exec ruby -Ilib:test test/action_controller/serialization_test.rb -n /test_render_with_cache_enable_and_expired/

diff --git a/lib/active_model_serializers/adapter/attributes.rb b/lib/active_model_serializers/adapter/attributes.rb
index cc8b807..10b265b 100644
--- a/lib/active_model_serializers/adapter/attributes.rb
+++ b/lib/active_model_serializers/adapter/attributes.rb
@@ -34,6 +34,7 @@ module ActiveModelSerializers
       def resource_relationships(options)
         relationships = {}
         serializer.associations(@include_tree).each do |association|
+          p association.key
           relationships[association.key] ||= relationship_value_for(association, options)
         end

diff --git a/test/action_controller/serialization_test.rb b/test/action_controller/serialization_test.rb
index aa7375f..39f9371 100644
--- a/test/action_controller/serialization_test.rb
+++ b/test/action_controller/serialization_test.rb
@@ -454,13 +454,15 @@ module ActionController
       end

       def test_render_event_is_emmited
-        ::ActiveSupport::Notifications.subscribe('render.active_model_serializers') do |name|
+        subscriber = ::ActiveSupport::Notifications.subscribe('render.active_model_serializers') do |name|
           @name = name
         end

         get :render_using_implicit_serializer

         assert_equal 'render.active_model_serializers', @name
+      ensure
+        ActiveSupport::Notifications.unsubscribe(subscriber)
       end
     end
   end

on master

:comments
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[beauby]

That's in two different calls (adding: p serializer.associations(@include_tree).map(&:key) to resource_relationships):

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[beauby]

Adding fail if relationships[association.key] inside the loop runs fine on the test suite.

[beauby]

Closing this one in favor of #1696.