1 files changed, 41 insertions, 0 deletions
diff --git a/lib/gitlab/action_view_output/context.rb b/lib/gitlab/action_view_output/context.rb
new file mode 100644
index 00000000000..9fbc9811636
--- /dev/null
+++ b/lib/gitlab/action_view_output/context.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+# This file was simplified from https://raw.githubusercontent.com/rails/rails/195f39804a7a4a0034f25e8704220e03d95a752a/actionview/lib/action_view/context.rb.
+#
+# It is only needed by modules that need to call ActionView helper
+# methods (e.g. those in
+# https://github.com/rails/rails/tree/c4d3e202e10ae627b3b9c34498afb45450652421/actionview/lib/action_view/helpers)
+# to generate tags outside of a Rails controller (e.g. API, Sidekiq,
+# etc.).
+#
+# In Rails 5, ActionView::Context automatically includes CompiledTemplates.
+# This means that any module that includes ActionView::Context is now a descendant
+# of CompiledTemplates.
+#
+# When a partial is rendered for the first time, it runs
+# Module#module_eval, which will evaluate a string source that defines a
+# new method. For example:
+#
+# def _app_views_profiles_show_html_haml___1285955918103175884_70307801785400(local_assigns, output_buffer)
+#   "hello world"
+# end
+#
+# When a new method is defined, the Ruby interpreter clears the method
+# cache for all descendants, and all methods for those modules will have
+# to be redefined.  This can lead to a significant performance penalty.
+#
+# Rails 6 fixes this behavior by moving out the `include
+# CompiledTemplates` into ActionView::Base so that including `ActionView::Context`
+# doesn't quietly affect other modules in this way.
+
+if Rails::VERSION::STRING.start_with?('6')
+  raise 'This module is no longer needed in Rails 6. Use ActionView::Context instead.'
+end
+
+module Gitlab
+  module ActionViewOutput
+    module Context
+      attr_accessor :output_buffer, :view_flow
+    end
+  end
+end