Make process_resource return an Array of hashes.

lib/active_model/serializer/adapter/json_api.rb

@@ -51,8 +51,7 @@ def initialize(serializer, options = {})
         def serializable_hash(options = nil)
           options ||= {}
 
-          resources = {}
-          process_resource(serializer, @include_tree, true, resources)
+          resources = process_resource(serializer)
           primary_data, included = resources.each_with_object([[], []]) do |(_, resource), (prim, incl)|
             is_primary = resource.delete(:is_primary)
             if is_primary
@@ -94,25 +93,27 @@ def fragment_cache(cached_hash, non_cached_hash)
         #    on included associations.
         #
         # @api private
-        def process_resource(serializer, include_tree, is_primary, hashes)
+        def process_resource(serializer, include_tree = @include_tree, is_primary = true, hashes = {})
           if serializer.respond_to?(:each)
             serializer.each { |s| process_resource(s, include_tree, is_primary, hashes) }
-            return
+            return hashes
           end
 
-          return unless serializer && serializer.object
+          return hashes unless serializer && serializer.object
 
           key = [resource_identifier_type_for(serializer), resource_identifier_id_for(serializer)]
           if hashes[key]
             hashes[key][:is_primary] ||= is_primary
-            return
+            return hashes
           end
 
           hashes[key] = resource_object_for(serializer).merge(is_primary: is_primary)
 
           serializer.associations(include_tree).each do |association|
             process_resource(association.serializer, include_tree[association.key], false, hashes)
           end
+
+          hashes
         end
 
         # Transform a serializer into a resource object.