Ensure current user and variables are updated when playing a job

Use `update!` instead of `update` to ensure that the job attributes
are updated successfully when playing a manual job.

Changelog: fixed

app/services/ci/play_build_service.rb

@@ -9,7 +9,7 @@ module Ci
       #
       if build.enqueue
         build.tap do |build|
-          build.update(user: current_user, job_variables_attributes: job_variables_attributes || [])
+          build.update!(user: current_user, job_variables_attributes: job_variables_attributes || [])
 
           AfterRequeueJobService.new(project, current_user).execute(build)
         end

spec/services/ci/play_build_service_spec.rb

@@ -79,12 +79,22 @@ RSpec.describe Ci::PlayBuildService, '#execute' do
          { key: 'second', secret_value: 'second' }]
       end
 
+      subject { service.execute(build, job_variables) }
+
       it 'assigns the variables to the build' do
-        service.execute(build, job_variables)
+        subject
 
         expect(build.reload.job_variables.map(&:key)).to contain_exactly('first', 'second')
       end
 
+      context 'when variables are invalid' do
+        let(:job_variables) { [{}] }
+
+        it 'raises an error' do
+          expect { subject }.to raise_error(ActiveRecord::RecordInvalid)
+        end
+      end
+
       context 'when user defined variables are restricted' do
         before do
           project.update!(restrict_user_defined_variables: true)
@@ -96,7 +106,7 @@ RSpec.describe Ci::PlayBuildService, '#execute' do
           end
 
           it 'assigns the variables to the build' do
-            service.execute(build, job_variables)
+            subject
 
             expect(build.reload.job_variables.map(&:key)).to contain_exactly('first', 'second')
           end
@@ -104,8 +114,7 @@ RSpec.describe Ci::PlayBuildService, '#execute' do
 
         context 'when user is developer' do
           it 'raises an error' do
-            expect { service.execute(build, job_variables) }
-              .to raise_error Gitlab::Access::AccessDeniedError
+            expect { subject }.to raise_error Gitlab::Access::AccessDeniedError
           end
         end
       end