Merge branch 'frontend-feature-flags' into 'master'

Support pushing of feature flags to the frontend

Closes gitlab-org/release/framework#17

See merge request gitlab-org/gitlab-ce!22197

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/gitlab/gon_helper.rb b/lib/gitlab/gon_helper.rb
index deaa14c8434..c1726659a90 100644
--- a/lib/gitlab/gon_helper.rb
+++ b/lib/gitlab/gon_helper.rb
@@ -30,5 +30,20 @@ module Gitlab
         gon.current_user_avatar_url = current_user.avatar_url
       end
     end
+
+    # Exposes the state of a feature flag to the frontend code.
+    #
+    # name - The name of the feature flag, e.g. `my_feature`.
+    # args - Any additional arguments to pass to `Feature.enabled?`. This allows
+    #        you to check if a flag is enabled for a particular user.
+    def push_frontend_feature_flag(name, *args)
+      var_name = name.to_s.camelize(:lower)
+      enabled = Feature.enabled?(name, *args)
+
+      # Here the `true` argument signals gon that the value should be merged
+      # into any existing ones, instead of overwriting them. This allows you to
+      # use this method to push multiple feature flags.
+      gon.push({ features: { var_name => enabled } }, true)
+    end
   end
 end