Send continue parameter on for cancel_path

In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21595
`ContinueParams` was introducted in the `Projects::JobController#cancel`
since `continue` parameter is not present for in `cancel_path` for
`Projects::JobController#show.sjon` the user is being redirect to the
pipeline page, where it should be redirected to the current job page
instead.

Add the `continue` parameter as a query string for `cancel_path`.

app/serializers/job_entity.rb

@@ -9,7 +9,7 @@ class JobEntity < Grape::Entity
   expose :started?, as: :started
 
   expose :build_path do |build|
-    build.target_url || path_to(:namespace_project_job, build)
+    build_path(build)
   end
 
   expose :retry_path, if: -> (*) { retryable? } do |build|
@@ -17,7 +17,11 @@ class JobEntity < Grape::Entity
   end
 
   expose :cancel_path, if: -> (*) { cancelable? } do |build|
-    path_to(:cancel_namespace_project_job, build)
+    path_to(
+      :cancel_namespace_project_job,
+      build,
+      { continue: { to: build_path(build) } }
+    )
   end
 
   expose :play_path, if: -> (*) { playable? } do |build|
@@ -60,8 +64,12 @@ class JobEntity < Grape::Entity
     build.detailed_status(request.current_user)
   end
 
-  def path_to(route, build)
-    send("#{route}_path", build.project.namespace, build.project, build) # rubocop:disable GitlabSecurity/PublicSend
+  def path_to(route, build, params = {})
+    send("#{route}_path", build.project.namespace, build.project, build, params) # rubocop:disable GitlabSecurity/PublicSend
+  end
+
+  def build_path(build)
+    build.target_url || path_to(:namespace_project_job, build)
   end
 
   def failed?

spec/controllers/projects/jobs_controller_spec.rb

@@ -157,6 +157,28 @@ describe Projects::JobsController, :clean_gitlab_redis_shared_state do
         end
       end
 
+      context 'when job is running' do
+        context 'job is cancelable' do
+          let(:job) { create(:ci_build, :running, pipeline: pipeline) }
+
+          it 'cancel_path is present with correct redirect' do
+            expect(response).to have_gitlab_http_status(:ok)
+            expect(response).to match_response_schema('job/job_details')
+            expect(json_response['cancel_path']).to include(CGI.escape(json_response['build_path']))
+          end
+        end
+
+        context 'with web terminal' do
+          let(:job) { create(:ci_build, :running, :with_runner_session, pipeline: pipeline) }
+
+          it 'exposes the terminal path' do
+            expect(response).to have_gitlab_http_status(:ok)
+            expect(response).to match_response_schema('job/job_details')
+            expect(json_response['terminal_path']).to match(%r{/terminal})
+          end
+        end
+      end
+
       context 'when job has artifacts' do
         context 'with not expiry date' do
           let(:job) { create(:ci_build, :success, :artifacts, pipeline: pipeline) }
@@ -185,16 +207,6 @@ describe Projects::JobsController, :clean_gitlab_redis_shared_state do
         end
       end
 
-      context 'when job has terminal' do
-        let(:job) { create(:ci_build, :running, :with_runner_session, pipeline: pipeline) }
-
-        it 'exposes the terminal path' do
-          expect(response).to have_gitlab_http_status(:ok)
-          expect(response).to match_response_schema('job/job_details')
-          expect(json_response['terminal_path']).to match(%r{/terminal})
-        end
-      end
-
       context 'when job passed with no trace' do
         let(:job) { create(:ci_build, :success, :artifacts, pipeline: pipeline) }
 

spec/features/projects/jobs_spec.rb

@@ -198,6 +198,24 @@ describe 'Jobs', :clean_gitlab_redis_shared_state do
       end
     end
 
+    context 'when job is running', :js do
+      let(:job) { create(:ci_build, :running, pipeline: pipeline) }
+      let(:job_url) { project_job_path(project, job) }
+
+      before do
+        visit job_url
+        wait_for_requests
+      end
+
+      context 'job is cancelable' do
+        it 'shows cancel button' do
+          click_link 'Cancel'
+
+          expect(page.current_path).to eq(job_url)
+        end
+      end
+    end
+
     context "Job from other project" do
       before do
         visit project_job_path(project, job2)