Free up `labels` as a group name

config/routes/group.rb

@@ -34,10 +34,6 @@ constraints(GroupUrlConstrainer.new) do
       end
     end
 
-    resources :labels, except: [:show] do
-      post :toggle_subscription, on: :member
-    end
-
     scope path: '-' do
       namespace :settings do
         resource :ci_cd, only: [:show], controller: 'ci_cd'
@@ -46,6 +42,10 @@ constraints(GroupUrlConstrainer.new) do
       resources :variables, only: [:index, :show, :update, :create, :destroy]
 
       resources :children, only: [:index]
+
+      resources :labels, except: [:show] do
+        post :toggle_subscription, on: :member
+      end
     end
   end
 
@@ -58,4 +58,10 @@ constraints(GroupUrlConstrainer.new) do
     put '/', action: :update
     delete '/', action: :destroy
   end
+
+  # Legacy paths should be defined last, so they would be ignored if routes with
+  # one of the previously reserved words exist.
+  scope(path: 'groups/*group_id') do
+    Gitlab::Routing.redirect_legacy_paths(self, :labels)
+  end
 end

lib/gitlab/path_regex.rb

@@ -120,7 +120,6 @@ module Gitlab
       group_members
       hooks
       issues
-      labels
       ldap
       ldap_group_links
       merge_requests

spec/routing/group_routing_spec.rb

+require 'spec_helper'
+
+describe 'group routing' do
+  let!(:existing_group) { create(:group, parent: create(:group, path: 'gitlab-org'), path: 'infra') }
+
+  describe 'GET #labels' do
+    it 'routes to the correct controller' do
+      expect(get('/groups/gitlab-org/infra/-/labels'))
+        .to route_to(group_id: 'gitlab-org/infra',
+                     controller: 'groups/labels',
+                     action: 'index')
+    end
+
+    it_behaves_like 'redirecting a legacy path', '/groups/gitlab-org/infra/labels', '/groups/gitlab-org/infra/-/labels' do
+      let(:resource) { create(:group, parent: existing_group, path: 'labels') }
+    end
+  end
+end