Add active blocks list api endpoint with empty response

app/abilities/api_ability.rb

@@ -30,6 +30,8 @@ class ApiAbility
         can [:read, :update, :destroy], Message if scopes.include?("consume_messages")
         can :create, Message if scopes.include?("send_messages")
 
+        can :read, :active_user_blocks_list if scopes.include?("read_prefs")
+
         if user.terms_agreed?
           can [:create, :update, :upload, :close, :subscribe, :unsubscribe], Changeset if scopes.include?("write_map")
           can :create, ChangesetComment if scopes.include?("write_changeset_comments")

app/controllers/api/user_blocks/active_lists_controller.rb

@@ -0,0 +1,13 @@
+module Api
+  module UserBlocks
+    class ActiveListsController < ApiController
+      before_action :authorize
+
+      authorize_resource :class => :active_user_blocks_list
+
+      before_action :set_request_formats
+
+      def show; end
+    end
+  end
+end

config/routes.rb

@@ -122,6 +122,9 @@ OpenStreetMap::Application.routes.draw do
     end
 
     resources :user_blocks, :only => :show, :id => /\d+/, :controller => "user_blocks"
+    namespace :user_blocks, :path => "user/blocks" do
+      resource :active_list, :path => "active", :only => :show
+    end
   end
 
   # Data browsing

test/controllers/api/user_blocks/active_lists_controller_test.rb

@@ -0,0 +1,43 @@
+require "test_helper"
+
+module Api
+  module UserBlocks
+    class ActiveListsControllerTest < ActionDispatch::IntegrationTest
+      ##
+      # test all routes which lead to this controller
+      def test_routes
+        assert_routing(
+          { :path => "/api/0.6/user/blocks/active", :method => :get },
+          { :controller => "api/user_blocks/active_lists", :action => "show" }
+        )
+        assert_routing(
+          { :path => "/api/0.6/user/blocks/active.json", :method => :get },
+          { :controller => "api/user_blocks/active_lists", :action => "show", :format => "json" }
+        )
+      end
+
+      def test_show_no_auth_header
+        get api_user_blocks_active_list_path
+        assert_response :unauthorized
+      end
+
+      def test_show_no_permission
+        user = create(:user)
+        user_auth_header = bearer_authorization_header(user, :scopes => %w[])
+
+        get api_user_blocks_active_list_path, :headers => user_auth_header
+        assert_response :forbidden
+      end
+
+      def test_show_empty
+        user = create(:user)
+        user_auth_header = bearer_authorization_header(user, :scopes => %w[read_prefs])
+        create(:user_block, :expired, :user => user)
+
+        get api_user_blocks_active_list_path, :headers => user_auth_header
+        assert_response :success
+        assert_dom "user_block", :count => 0
+      end
+    end
+  end
+end