Load the Merge Request > Commits tab lazily

app/controllers/projects/merge_requests_controller.rb

@@ -71,7 +71,10 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def commits
-    render 'show'
+    respond_to do |format|
+      format.html { render 'show' }
+      format.json { render json: { html: view_to_html_string('projects/merge_requests/show/_commits') } }
+    end
   end
 
   def new

app/views/projects/merge_requests/_show.html.haml

@@ -56,6 +56,7 @@
     #notes.notes.tab-pane.voting_notes
       = render "projects/merge_requests/discussion"
     #commits.commits.tab-pane
+      - if current_page?(action: 'commits')
         = render "projects/merge_requests/show/commits"
     #diffs.diffs.tab-pane
       - if current_page?(action: 'diffs')
@@ -64,7 +65,6 @@
   .mr-loading-status
     = spinner
 
-
 :javascript
   var merge_request;
 

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -79,8 +79,32 @@ describe Projects::MergeRequestsController do
     end
   end
 
-  context '#diffs with forked projects with submodules' do
+  describe 'GET diffs' do
+    def go(format: 'html')
+      get :diffs, namespace_id: project.namespace.to_param,
+        project_id: project.to_param, id: merge_request.iid, format: format
+    end
+
+    context 'as html' do
+      it 'renders the diff template' do
+        go
+
+        expect(response).to render_template('diffs')
+      end
+    end
+
+    context 'as json' do
+      it 'renders the diffs template to a string' do
+        go format: 'json'
+
+        expect(response).to render_template('projects/merge_requests/show/_diffs')
+        expect(JSON.parse(response.body)).to have_key('html')
+      end
+    end
+
+    context 'with forked projects with submodules' do
       render_views
+
       let(:project) { create(:project) }
       let(:fork_project) { create(:forked_project_with_submodules) }
       let(:merge_request) { create(:merge_request_with_diffs, source_project: fork_project, source_branch: 'add-submodule-version-bump', target_branch: 'master', target_project: project) }
@@ -91,11 +115,36 @@ describe Projects::MergeRequestsController do
         merge_request.reload
       end
 
-    it '#diffs' do
-      get(:diffs, namespace_id: project.namespace.to_param,
-          project_id: project.to_param, id: merge_request.iid, format: 'json')
+      it 'renders' do
+        go format: 'json'
+
         expect(response).to be_success
         expect(response.body).to have_content('Subproject commit')
       end
     end
+  end
+
+  describe 'GET commits' do
+    def go(format: 'html')
+      get :commits, namespace_id: project.namespace.to_param,
+        project_id: project.to_param, id: merge_request.iid, format: format
+    end
+
+    context 'as html' do
+      it 'renders the show template' do
+        go
+
+        expect(response).to render_template('show')
+      end
+    end
+
+    context 'as json' do
+      it 'renders the commits template to a string' do
+        go format: 'json'
+
+        expect(response).to render_template('projects/merge_requests/show/_commits')
+        expect(JSON.parse(response.body)).to have_key('html')
+      end
+    end
+  end
 end