Keep check answers referrer when validation is hit

app/helpers/merge_requests_helper.rb

@@ -74,4 +74,8 @@ module MergeRequestsHelper
       { text: "Change", href: send("#{page}_merge_request_path", merge_request, referrer: "check_answers"), visually_hidden_text: page.humanize }
     end
   end
+
+  def submit_merge_request_url(referrer)
+    referrer == "check_answers" ? merge_request_path(referrer: "check_answers") : merge_request_path
+  end
 end

app/views/merge_requests/absorbing_organisation.html.erb

@@ -4,7 +4,7 @@
   <%= govuk_back_link href: merge_request_back_link(@merge_request, "absorbing_organisation", request.query_parameters["referrer"]) %>
 <% end %>
 
-<%= form_with model: @merge_request, url: merge_request_path, method: :patch do |f| %>
+<%= form_with model: @merge_request, url: submit_merge_request_url(request.query_parameters["referrer"]), method: :patch do |f| %>
   <%= f.govuk_error_summary %>
 
   <h1 class="govuk-heading-l">Which organisation is absorbing the others?</h1>

app/views/merge_requests/helpdesk_ticket.html.erb

@@ -4,7 +4,7 @@
   <%= govuk_back_link href: merge_request_back_link(@merge_request, "helpdesk_ticket", request.query_parameters["referrer"]) %>
 <% end %>
 
-<%= form_with model: @merge_request, url: merge_request_path, method: :patch do |f| %>
+<%= form_with model: @merge_request, url: submit_merge_request_url(request.query_parameters["referrer"]), method: :patch do |f| %>
   <%= f.govuk_error_summary %>
 
   <h1 class="govuk-heading-l">Which helpdesk ticket reported this merge?</h1>

app/views/merge_requests/merge_date.html.erb

@@ -5,7 +5,7 @@
 <% end %>
  <div class="govuk-grid-row">
     <div class="govuk-grid-column-two-thirds-from-desktop">
-    <%= form_with model: @merge_request, url: merge_request_path, method: :patch do |f| %>
+    <%= form_with model: @merge_request, url: submit_merge_request_url(request.query_parameters["referrer"]), method: :patch do |f| %>
       <%= f.govuk_error_summary %>
 
       <h2 class="govuk-heading-l">What is the merge date?</h2>

spec/requests/merge_requests_controller_spec.rb

@@ -276,6 +276,24 @@ RSpec.describe MergeRequestsController, type: :request do
             }.from(nil).to(other_organisation)
           end
         end
+
+        context "when updating from check_answers page" do
+          let(:merge_request) { MergeRequest.create!(requesting_organisation: organisation) }
+          let(:params) do
+            { merge_request: { absorbing_organisation_id: "", page: "absorbing_organisation" } }
+          end
+
+          let(:request) do
+            patch "/merge-request/#{merge_request.id}?referrer=check_answers", headers:, params:
+          end
+
+          it "keeps corrent links if validation fails" do
+            request
+
+            expect(page).to have_link("Cancel", href: merge_request_path(merge_request))
+            expect(page).to have_button("Save changes")
+          end
+        end
       end
 
       describe "from merge_date page" do