Added a small helper to reduce logic in the view

app/helpers/milestones_helper.rb

@@ -47,6 +47,17 @@ module MilestonesHelper
     }
   end
+  # Show 'active' class if provided GET param matches check
+  # `or_blank` allows the function to return 'active' when given an empty param
+  # Could be refactored to be simpler but that may make it harder to read
+  def milestone_class_for_state(param, check, match_blank_param=false)
+    if match_blank_param
+      'active' if param.blank? || param == check
+    else
+      'active' if param == check
+    end
+  end
+
   def milestone_progress_bar(milestone)
     options = {
       class: 'progress-bar progress-bar-success',

app/views/shared/_milestones_filter.html.haml

@@ -2,17 +2,17 @@
   - counts = milestone_counts(@project.milestones)
 %ul.nav-links
-  %li{class: ("active" if params[:state].blank? || params[:state] == 'opened')}
+  %li{class: milestone_class_for_state(params[:state], 'opened', true)}
     = link_to milestones_filter_path(state: 'opened') do
       Open
       - if @project
         %span.badge #{counts[:opened]}
-  %li{class: ("active" if params[:state] == 'closed')}
+  %li{class: milestone_class_for_state(params[:state], 'closed')}
     = link_to milestones_filter_path(state: 'closed') do
       Closed
       - if @project
         %span.badge #{counts[:closed]}
-  %li{class: ("active" if params[:state] == 'all')}
+  %li{class: milestone_class_for_state(params[:state], 'all')}
     = link_to milestones_filter_path(state: 'all') do
       All
       - if @project