Fix merge request new view not changing code view rendering style

CHANGELOG

@@ -75,6 +75,7 @@ v 8.11.0 (unreleased)
   - Speedup DiffNote#active? on discussions, preloading noteables and avoid touching git repository to return diff_refs when possible
   - Add commit stats in commit api. !5517 (dixpac)
   - Add CI configuration button on project page
+  - Fix merge request new view not changing code view rendering style
   - Make error pages responsive (Takuya Noguchi)
   - Fix skip_repo parameter being ignored when destroying a namespace
   - Change requests_profiles resource constraint to catch virtually any file

app/controllers/projects/merge_requests_controller.rb

@@ -142,6 +142,8 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def new
+    apply_diff_view_cookie!
+
     build_merge_request
     @noteable = @merge_request
 

spec/features/merge_requests/create_new_mr_spec.rb

@@ -8,10 +8,11 @@ feature 'Create New Merge Request', feature: true, js: true do
     project.team << [user, :master]
 
     login_as user
-    visit namespace_project_merge_requests_path(project.namespace, project)
   end
 
   it 'generates a diff for an orphaned branch' do
+    visit namespace_project_merge_requests_path(project.namespace, project)
+
     click_link 'New Merge Request'
 
     first('.js-source-branch').click
@@ -40,4 +41,20 @@ feature 'Create New Merge Request', feature: true, js: true do
       expect(page).not_to have_content private_project.to_reference
     end
   end
+
+  it 'allows to change the diff view' do
+    visit new_namespace_project_merge_request_path(project.namespace, project, merge_request: { target_branch: 'master', source_branch: 'fix' })
+
+    click_link 'Changes'
+
+    expect(page.find_link('Inline')[:class]).to match(/\bactive\b/)
+    expect(page.find_link('Side-by-side')[:class]).not_to match(/\bactive\b/)
+
+    click_link 'Side-by-side'
+
+    click_link 'Changes'
+
+    expect(page.find_link('Inline')[:class]).not_to match(/\bactive\b/)
+    expect(page.find_link('Side-by-side')[:class]).to match(/\bactive\b/)
+  end
 end