Use generic update method

app/controllers/merge_requests_controller.rb

@@ -1,6 +1,7 @@
 class MergeRequestsController < ApplicationController
   before_action :authenticate_user!
-  before_action :find_resource, only: %i[organisations update_organisations remove_merging_organisation update_other_merging_organisations]
+  before_action :find_resource, only: %i[organisations update_organisations remove_merging_organisation]
+  before_action :find_resource_by_id, only: %i[update]
 
   def create
     @merge_request = MergeRequest.create!(merge_request_params)
@@ -13,6 +14,14 @@ class MergeRequestsController < ApplicationController
     @merging_organisations_list = [@merge_request.requesting_organisation] + @merge_request.merging_organisations
   end
 
+  def update
+    if @merge_request.update(merge_request_params)
+      redirect_to next_page_path
+    else
+      render previous_template, status: :unprocessable_entity
+    end
+  end
+
   def update_organisations
     merge_request_organisation = MergeRequestOrganisation.new(merge_request_organisation_params)
     @answer_options = organisations_answer_options
@@ -26,14 +35,6 @@ class MergeRequestsController < ApplicationController
     end
   end
 
-  def update_other_merging_organisations
-    if @merge_request.update(other_merging_organisaitions_params)
-      redirect_to merge_request_absorbing_organisation_path(@merge_request)
-    else
-      render :organisations, status: :unprocessable_entity
-    end
-  end
-
   def remove_merging_organisation
     MergeRequestOrganisation.find_by(merge_request_organisation_params).destroy!
     @merge_request.reload
@@ -56,7 +57,7 @@ private
   def merge_request_params
     merge_params = params.fetch(:merge_request, {}).permit(:requesting_organisation_id, :other_merging_organisations)
 
-    if current_user.data_coordinator? || current_user.data_provider?
+    if merge_params[:requesting_organisation_id].present? && (current_user.data_coordinator? || current_user.data_provider?)
       merge_params[:requesting_organisation_id] = current_user.organisation.id
     end
 
@@ -67,11 +68,19 @@ private
     { merge_request: @merge_request, merging_organisation_id: params[:merge_request][:merging_organisation] }
   end
 
-  def other_merging_organisaitions_params
-    params.fetch(:merge_request, {}).permit(:other_merging_organisations)
-  end
-
   def find_resource
     @merge_request = MergeRequest.find(params[:merge_request_id])
   end
+
+  def find_resource_by_id
+    @merge_request = MergeRequest.find(params[:id])
+  end
+
+  def next_page_path
+    merge_request_absorbing_organisation_path(@merge_request)
+  end
+
+  def previous_template
+    :organisations
+  end
 end

app/views/merge_requests/organisations.html.erb

@@ -45,7 +45,7 @@
     <% end %>
   <% end %>
 <% end %>
-<%= form_with model: @merge_request, url: merge_request_other_merging_organisations_path, method: :patch do |f| %>
+<%= form_with model: @merge_request, url: merge_request_path(id: @merge_request.id), method: :patch do |f| %>
   <%= govuk_details(summary_text: "Can't find the managing agent you're looking for?") do %>
     <%= f.govuk_text_area :other_merging_organisations, label: { text: "Other organisations" }, hint: { text: "List other organisations that are part of the merge but not registered on CORE." }, rows: 9 %>
   <% end %>

config/routes.rb

@@ -124,11 +124,9 @@ Rails.application.routes.draw do
   end
 
   resources :merge_requests, path: "/merge-request" do
-    post "merge-request", to: "merge_request#create_merge_request"
     get "organisations", to: "merge_requests#organisations"
     patch "organisations", to: "merge_requests#update_organisations"
     get "organisations/remove", to: "merge_requests#remove_merging_organisation"
-    patch "other-merging-organisations", to: "merge_requests#update_other_merging_organisations"
     get "absorbing-organisation", to: "merge_requests#absorbing_organisation"
   end
 

spec/requests/merge_requests_controller_spec.rb

@@ -15,7 +15,7 @@ RSpec.describe MergeRequestsController, type: :request do
     end
 
     describe "#organisations" do
-      let(:params) { {} }
+      let(:params) { { merge_request: { requesting_organisation_id: "9" } } }
 
       before do
         organisation.update!(name: "Test Org")
@@ -159,7 +159,7 @@ RSpec.describe MergeRequestsController, type: :request do
       context "when adding other merging organisations" do
         before do
           MergeRequestOrganisation.create!(merge_request_id: merge_request.id, merging_organisation_id: other_organisation.id)
-          patch "/merge-request/#{merge_request.id}/other-merging-organisations", headers:, params:
+          patch "/merge-request/#{merge_request.id}", headers:, params:
         end
 
         it "updates the merge request" do