Adds better error handling and refactors specs

* Applies suggestions
* Fixes rubocop formatting

app/graphql/mutations/ci/base.rb

@@ -3,7 +3,6 @@
 module Mutations
   module Ci
     class Base < BaseMutation
-
       argument :id, GraphQL::ID_TYPE,
                 required: true,
                 description: 'The id of the pipeline to mutate'

app/graphql/mutations/ci/pipeline_cancel.rb

@@ -8,13 +8,12 @@ module Mutations
       authorize :update_pipeline
 
       def resolve
-        ::Ci::CancelUserPipelinesService.new.execute(current_user)
+        result = ::Ci::CancelUserPipelinesService.new.execute(current_user)
 
         {
-          errors: []
+          errors: [result&.message]
         }
       end
-
     end
   end
 end

app/graphql/mutations/ci/pipeline_destroy.rb

@@ -12,11 +12,11 @@ module Mutations
         project = pipeline.project
 
         ::Ci::DestroyPipelineService.new(project, current_user).execute(pipeline)
+      rescue ActiveRecord::RecordNotFound
         {
-          errors: []
+          errors: ['Pipeline not found']
         }
       end
-
     end
   end
 end

app/graphql/mutations/ci/pipeline_retry.rb

@@ -17,7 +17,6 @@ module Mutations
           errors: errors_on_object(pipeline)
         }
       end
-
     end
   end
 end

app/services/ci/cancel_user_pipelines_service.rb

@@ -7,6 +7,8 @@ module Ci
     # https://gitlab.com/gitlab-org/gitlab/issues/32332
     def execute(user)
       user.pipelines.cancelable.find_each(&:cancel_running)
+    rescue ActiveRecord::StaleObjectError
+      ServiceResponse.error(message: 'Error canceling pipeline')
     end
     # rubocop: enable CodeReuse/ActiveRecord
   end

spec/requests/api/graphql/mutations/ci/pipeline_cancel_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'PipelineCancel' do
 
   let_it_be(:user) { create(:user) }
   let_it_be(:project) { create(:project) }
-  let(:pipeline) { create(:ci_pipeline, :running, project: project, user: user) }
+  let_it_be(:pipeline) { create(:ci_pipeline, :running, project: project, user: user) }
 
   let(:mutation) do
     graphql_mutation(:pipeline_cancel, {},
@@ -17,10 +17,21 @@ RSpec.describe 'PipelineCancel' do
     )
   end
 
-  before do
+  let(:mutation_response) { graphql_mutation_response(:pipeline_cancel) }
+
+  before(:all) do
     project.add_maintainer(user)
   end
 
+  it 'reports the service-level error' do
+    service = double(execute: ServiceResponse.error(message: 'Error canceling pipeline'))
+    allow(::Ci::CancelUserPipelinesService).to receive(:new).and_return(service)
+
+    post_graphql_mutation(mutation, current_user: create(:user))
+
+    expect(mutation_response).to include('errors' => ['Error canceling pipeline'])
+  end
+
   it 'does not change any pipelines not owned by the current user' do
     build = create(:ci_build, :running, pipeline: pipeline)
 

spec/requests/api/graphql/mutations/ci/pipeline_destroy_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'PipelineDestroy' do
 
   let_it_be(:project) { create(:project) }
   let_it_be(:user) { project.owner }
-  let(:pipeline) { create(:ci_pipeline, :success, project: project, user: user) }
+  let_it_be(:pipeline) { create(:ci_pipeline, :success, project: project, user: user) }
 
   let(:mutation) do
     variables = {

spec/requests/api/graphql/mutations/ci/pipeline_retry_spec.rb

@@ -7,7 +7,7 @@ RSpec.describe 'PipelineRetry' do
 
   let_it_be(:user) { create(:user) }
   let_it_be(:project) { create(:project) }
-  let(:pipeline) { create(:ci_pipeline,  project: project, user: user) }
+  let_it_be(:pipeline) { create(:ci_pipeline, project: project, user: user) }
 
   let(:mutation) do
     variables = {
@@ -25,7 +25,7 @@ RSpec.describe 'PipelineRetry' do
 
   let(:mutation_response) { graphql_mutation_response(:pipeline_retry) }
 
-  before do
+  before(:all) do
     project.add_maintainer(user)
   end
 

spec/services/ci/cancel_user_pipelines_service_spec.rb

@@ -19,5 +19,17 @@ RSpec.describe Ci::CancelUserPipelinesService do
         expect(build.reload).to be_canceled
       end
     end
+
+    context 'when an error ocurrs' do
+      it 'raises a service level error' do
+        service = double(execute: ServiceResponse.error(message: 'Error canceling pipeline'))
+        allow(::Ci::CancelUserPipelinesService).to receive(:new).and_return(service)
+
+        result = subject
+
+        expect(result).to be_a(ServiceResponse)
+        expect(result).to be_error
+      end
+    end
   end
 end