Disallow enqueuing builds that are waiting for deployment approval

app/models/ci/build.rb

@@ -268,6 +268,10 @@ def with_preloads
         !build.any_unmet_prerequisites? # If false is returned, it stops the transition
       end
+      before_transition on: :enqueue do |build|
+        !build.waiting_for_deployment_approval? # If false is returned, it stops the transition
+      end
+
       after_transition created: :scheduled do |build|
         build.run_after_commit do
           Ci::BuildScheduleWorker.perform_at(build.scheduled_at, build.id)
@@ -424,7 +428,7 @@ def archived?
     end
     def playable?
-      action? && !archived? && (manual? || scheduled? || retryable?)
+      action? && !archived? && (manual? || scheduled? || retryable?) && !waiting_for_deployment_approval?
     end
     def waiting_for_deployment_approval?

app/models/deployment.rb

@@ -70,6 +70,10 @@ class Deployment < ApplicationRecord
       transition created: :blocked
     end
+    event :unblock do
+      transition blocked: :created
+    end
+
     event :succeed do
       transition any - [:success] => :success
     end

ee/app/services/deployments/approval_service.rb

@@ -32,6 +32,7 @@ def process_build!(deployment, approval)
       if approval.rejected?
         deployment.deployable.drop!(:deployment_rejected)
       elsif deployment.pending_approval_count <= 0
+        deployment.unblock!
         deployment.deployable.enqueue!
       end
     end

ee/spec/services/deployments/approval_service_spec.rb

@@ -103,9 +103,11 @@
         let(:required_approval_count) { 1 }
         it 'enqueues the build' do
-          subject
-          expect(deployment.deployable.status).to eq('pending')
+          expect { subject }.to change { deployment.deployable.status }.from('manual').to('pending')
+        end
+        it 'unblocks the deployment' do
+          expect { subject }.to change { deployment.status }.from('blocked').to('created')
         end
       end

spec/models/ci/build_spec.rb

@@ -2468,6 +2468,16 @@
       it { is_expected.not_to be_playable }
     end
+
+    context 'when build is waiting for deployment approval' do
+      subject { build_stubbed(:ci_build, :manual, environment: 'production') }
+
+      before do
+        create(:deployment, :blocked, deployable: subject)
+      end
+
+      it { is_expected.not_to be_playable }
+    end
   end
   describe 'project settings' do
@@ -3792,6 +3802,18 @@
     end
   end
+  describe 'when the build is waiting for deployment approval' do
+    let(:build) { create(:ci_build, :manual, environment: 'production') }
+
+    before do
+      create(:deployment, :blocked, deployable: build)
+    end
+
+    it 'does not allow the build to be enqueued' do
+      expect { build.enqueue! }.to raise_error(StateMachines::InvalidTransition)
+    end
+  end
+
   describe 'state transition: any => [:pending]' do
     let(:build) { create(:ci_build, :created) }