Display a friendly message when a report times out

Once we get a download link for a report, we can display this message
sooner. But for now we just use the existing request timeout.

app/controllers/admin/reports_controller.rb

@@ -26,6 +26,8 @@ module Admin
       else
         show_report
       end
+    rescue Rack::Timeout::RequestTimeoutException
+      render_timeout_error
     end
 
     private
@@ -36,6 +38,7 @@ module Admin
 
     def show_report
       assign_view_data
+      @table = render_report_as(:html) if render_data?
       render "show"
     end
 
@@ -45,7 +48,6 @@ module Admin
       @report_subtype = report_subtype
       @report_title = report_title
       @rendering_options = rendering_options
-      @table = render_report_as(:html) if render_data?
       @data = Reporting::FrontendData.new(spree_current_user)
     end
 
@@ -66,5 +68,11 @@ module Admin
         @report.render_as(format)
       end
     end
+
+    def render_timeout_error
+      assign_view_data
+      @error = ".report_taking_longer"
+      render "show"
+    end
   end
 end

app/views/admin/reports/show.html.haml

@@ -18,7 +18,8 @@
 .report__header.print-hidden
   - if @report.message.present?
     %p.report__message= @report.message
-  - if request.post?
+  - if request.post? && !@error
     %button.btn-print.icon-print{ onclick: "window.print()"}= t(:report_print)
 
+= t(@error) if @error
 = @table

config/locales/en.yml

@@ -1438,6 +1438,11 @@ en:
       pack_by_customer: Pack By Customer
       pack_by_supplier: Pack By Supplier
       pack_by_product: Pack By Product
+      show:
+        report_taking_longer: >
+          This report is taking longer to process.
+          It may contain a lot of data or we are busy with other reports.
+          You can try again later.
       revenues_by_hub:
         name: Revenues By Hub
         description: Revenues by hub

spec/system/admin/reports_spec.rb

@@ -44,6 +44,19 @@ describe '
       click_button "Go"
       expect(page).to have_content "EMAIL FIRST NAME"
     end
+
+    it "displays a friendly timeout message" do
+      ActiveJob::Base.queue_adapter.perform_enqueued_jobs = false
+      login_as_admin_and_visit admin_report_path(
+        report_type: :customers, report_subtype: :mailing_list
+      )
+      expect_any_instance_of(Admin::ReportsController).to receive(:sleep).
+        and_raise(Rack::Timeout::RequestTimeoutException.new(nil))
+
+      click_button "Go"
+
+      expect(page).to have_content "This report is taking longer to process."
+    end
   end
 
   describe "Can access Customers reports and generate customers report" do