1 files changed, 23 insertions, 4 deletions
diff --git a/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb b/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
index c95808a219..4781832711 100644
--- a/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
+++ b/actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb
@@ -33,13 +33,32 @@ module ActionView
               all_asset_files = (collect_asset_files(custom_dir, ('**' if recursive), "*.#{extension}") - ['application']) << 'application'
               ((determine_source(:defaults, expansions).dup & all_asset_files) + all_asset_files).uniq
             else
-              expanded_sources = sources.collect do |source|
-                determine_source(source, expansions)
-              end.flatten
-              expanded_sources << "application" if sources.include?(:defaults) && File.exist?(File.join(custom_dir, "application.#{extension}"))
+              expanded_sources = sources.inject([]) do |list, source|
+                determined_source = determine_source(source, expansions)
+                update_source_list(list, determined_source)
+              end
+              add_application_js(expanded_sources, sources)
               expanded_sources
             end
           end
+
+          def update_source_list(list, source)
+            case source
+            when String
+              list.delete(source)
+              list << source
+            when Array
+              updated_sources = source - list
+              list.concat(updated_sources)
+            end
+          end
+
+          def add_application_js(expanded_sources, sources)
+            if sources.include?(:defaults) && File.exist?(File.join(custom_dir, "application.#{extension}"))
+              expanded_sources.delete('application')
+              expanded_sources << "application"
+            end
+          end
       end