prevent generating invoices when order's distributor can't generate invoices

app/controllers/spree/admin/invoices_controller.rb

@@ -19,8 +19,14 @@ module Spree
 
       def generate
         @order = Order.find_by(number: params[:order_id])
-        authorize! :invoice, @order
-        OrderInvoiceGenerator.new(@order).generate_or_update_latest_invoice
+        if @order.distributor.can_invoice?
+          authorize! :invoice, @order
+          OrderInvoiceGenerator.new(@order).generate_or_update_latest_invoice
+        else
+          flash[:error] = t(:must_have_valid_business_number,
+                            enterprise_name: @order.distributor.name)
+        end
+
         redirect_back(fallback_location: spree.admin_dashboard_path)
       end
 

spec/controllers/spree/admin/orders/invoices_spec.rb

@@ -158,6 +158,10 @@ describe Spree::Admin::InvoicesController, type: :controller do
     let(:distributor) { order.distributor }
     let(:params) { { order_id: order.number } }
 
+    before do
+      distributor.update_attribute(:abn, "123412341234")
+    end
+
     context "as a normal user" do
       before { allow(controller).to receive(:spree_current_user) { user } }
 
@@ -193,6 +197,22 @@ describe Spree::Admin::InvoicesController, type: :controller do
 
           expect(response).to redirect_to spree.admin_dashboard_path
         end
+
+        context "distributor didn't set an ABN" do
+          before do
+            distributor.update_attribute(:abn, "")
+          end
+
+          it "should not allow me to generate a new invoice for the order" do
+            expect do
+              spree_get :generate, params
+            end.to change{ Invoice.count }.by(0)
+
+            expect(response).to redirect_to spree.admin_dashboard_path
+            expect(flash[:error])
+              .to eq "#{distributor.name} must have a valid ABN before invoices can be used."
+          end
+        end
       end
     end
   end