Detect invalid roll out status requests

Basically, if we can't find a pod with the given filter, we know the
status is invallid, so the exposed 'valid' flag will be false.

By @ayufan dupped as 'case 2', the last case to cover before the release
will be done in a seperate MR.

app/serializers/rollout_status_entity.rb

@@ -3,6 +3,7 @@ class RolloutStatusEntity < Grape::Entity
 
   expose :instances
   expose :completion
+  expose :valid?, as: :valid
 
   expose :is_completed do |rollout_status|
     rollout_status.complete?

changelogs/unreleased-ee/zj-kubernetes-rollout-invalid.yml

+---
+title: Set deployment status invalid when the environments does not match a k8s label
+merge_request:
+author:

lib/gitlab/kubernetes/rollout_status.rb

@@ -12,20 +12,27 @@ module Gitlab
         completion == 100
       end
 
+      def valid?
+        @valid
+      end
+
       def self.from_specs(*specs)
+        return new([], valid: false) if specs.empty?
+
         deployments = specs.map { |spec| ::Gitlab::Kubernetes::Deployment.new(spec) }
         new(deployments)
       end
 
-      def initialize(deployments)
-        @deployments = deployments
-        @instances = deployments.flat_map(&:instances)
+      def initialize(deployments, valid: true)
+        @valid        = valid
+        @deployments  = deployments
+        @instances    = deployments.flat_map(&:instances)
 
         @completion =
           if @instances.empty?
             100
           else
-            finished = @instances.select {|instance| instance[:status] == 'finished' }.count
+            finished = @instances.select { |instance| instance[:status] == 'finished' }.count
 
             (finished / @instances.count.to_f * 100).to_i
           end

spec/lib/gitlab/kubernetes/rollout_status_spec.rb

@@ -11,6 +11,8 @@ describe Gitlab::Kubernetes::RolloutStatus do
   end
 
   let(:specs) { specs_all_finished }
+  let(:specs_none) { [] }
+
   subject(:rollout_status) { described_class.from_specs(*specs) }
 
   describe '#deployments' do
@@ -61,4 +63,16 @@ describe Gitlab::Kubernetes::RolloutStatus do
       it { is_expected.to be_falsy}
     end
   end
+
+  describe '#valid?' do
+    context 'when the specs are passed' do
+      it { is_expected.to be_valid }
+    end
+
+    context 'when no specs are passed' do
+      let(:specs) { specs_none }
+
+      it { is_expected.not_to be_valid }
+    end
+  end
 end

spec/serializers/rollout_status_entity_spec.rb

@@ -13,4 +13,5 @@ describe RolloutStatusEntity do
   it { is_expected.to have_key(:instances) }
   it { is_expected.to have_key(:completion) }
   it { is_expected.to have_key(:is_completed) }
+  it { is_expected.to have_key(:valid) }
 end