Drop support for CanCanCan legacy can :dashboard style dashboard ability

This reverts commit da0584a.

Author: mshibuya

lib/rails_admin/extensions/cancancan/authorization_adapter.rb

@@ -26,12 +26,8 @@ def initialize(controller, ability = ::Ability)
         # instance if it is available.
         def authorize(action, abstract_model = nil, model_object = nil)
           return unless action
-          subject = model_object || abstract_model && abstract_model.model
-          if authorized_for_dashboard_in_legacy_way?(action)
-            subject
-          else
-            @controller.current_ability.authorize!(*resolve_with_compatibility(action, subject))
-          end
+          action, subject = resolve_action_and_subject(action, abstract_model, model_object)
+          @controller.current_ability.authorize!(action, subject)
         end
 
         # This method is called primarily from the view to determine whether the given user
@@ -40,9 +36,8 @@ def authorize(action, abstract_model = nil, model_object = nil)
         # return a boolean whereas +authorize+ will raise an exception when not authorized.
         def authorized?(action, abstract_model = nil, model_object = nil)
           return unless action
-          subject = model_object || abstract_model && abstract_model.model
-          authorized_for_dashboard_in_legacy_way?(action, true) ||
-            @controller.current_ability.can?(*resolve_with_compatibility(action, subject))
+          action, subject = resolve_action_and_subject(action, abstract_model, model_object)
+          @controller.current_ability.can?(action, subject)
         end
 
         # This is called when needing to scope a database query. It is called within the list
@@ -61,18 +56,8 @@ def attributes_for(action, abstract_model)
 
       private
 
-        def authorized_for_dashboard_in_legacy_way?(action, silent = false)
-          return false unless action == :dashboard
-          legacy_ability = @controller.current_ability.permissions[:can][:dashboard]
-          if legacy_ability && (legacy_ability.empty? || legacy_ability.all?(&:empty?))
-            ActiveSupport::Deprecation.warn('RailsAdmin CanCanCan Ability with `can :dashboard` is old and support will be removed in the next major release, use `can :read, :dashboard` instead. See https://github.com/sferik/rails_admin/issues/2901') unless silent
-            true
-          else
-            false
-          end
-        end
-
-        def resolve_with_compatibility(action, subject)
+        def resolve_action_and_subject(action, abstract_model, model_object)
+          subject = model_object || abstract_model && abstract_model.model
           if subject
             [action, subject]
           else

spec/integration/authorization/cancancan_spec.rb

@@ -340,27 +340,4 @@ def initialize(user)
       end
     end
   end
-
-  describe 'with existing dashboard ability which uses no subject' do
-    class LegacyDashboardAbility
-      include CanCan::Ability
-      def initialize(_)
-        can :access, :rails_admin
-        can :dashboard
-      end
-    end
-
-    before do
-      RailsAdmin.config { |c| c.authorize_with :cancancan, LegacyDashboardAbility }
-      @user = FactoryBot.create :user
-      login_as @user
-    end
-
-    it 'shows dashboard with instruction on how to migrate to new ability notation' do
-      allow(ActiveSupport::Deprecation).to receive(:warn)
-      expect(ActiveSupport::Deprecation).to receive(:warn).with(/can :read, :dashboard/)
-      visit dashboard_path
-      is_expected.to have_content('Dashboard')
-    end
-  end if CanCan::VERSION < '3'
 end