Ensure root container repository when visiting registry

Root container repository is a images repository that had been created
before 9.1, before we introduced multi-level images support.

app/controllers/projects/registry/repositories_controller.rb

@@ -2,6 +2,7 @@ module Projects
   module Registry
     class RepositoriesController < ::Projects::Registry::ApplicationController
       before_action :authorize_update_container_image!, only: [:destroy]
+      before_action :ensure_root_container_repository!, only: [:index]
       def index
         @images = project.container_repositories
@@ -22,6 +23,21 @@ module Projects
       def image
         @image ||= project.container_repositories.find_by(id: params[:id])
       end
+
+      ##
+      # Container repository object for root project path.
+      #
+      # Needed to maintain a backwards compatibility.
+      #
+      def ensure_root_container_repository!
+        ContainerRegistry::Path.new(@project.full_path).tap do |path|
+          return if path.has_repository?
+
+          ContainerRepository.build_from_path(path).tap do |repository|
+            repository.save if repository.has_tags?
+          end
+        end
+      end
     end
   end
 end

app/models/container_repository.rb

@@ -48,6 +48,10 @@ class ContainerRepository < ActiveRecord::Base
     tags.to_a.any?
   end
+  def root_repository?
+    name.empty?
+  end
+
   def delete_tags!
     return unless has_tags?
@@ -58,8 +62,12 @@ class ContainerRepository < ActiveRecord::Base
     end
   end
+  def self.build_from_path(path)
+    self.new(project: path.repository_project,
+             name: path.repository_name)
+  end
+
   def self.create_from_path!(path)
-    self.create(project: path.repository_project,
-                name: path.repository_name)
+    build_from_path(path).tap(&:save!)
   end
 end

spec/controllers/projects/registry/repositories_controller_spec.rb

+require 'spec_helper'
+
+describe Projects::Registry::RepositoriesController do
+  let(:user)    { create(:user) }
+  let(:project) { create(:empty_project, :private) }
+
+  before do
+    sign_in(user)
+  end
+
+  context 'when user has access to registry' do
+    before do
+      project.add_developer(user)
+    end
+
+    describe 'GET index' do
+      context 'when root container repository exists' do
+        before do
+          create(:container_repository, :root, project: project)
+        end
+
+        it 'does not create root container repository' do
+          expect { go_to_index }.not_to change { ContainerRepository.all.count }
+        end
+      end
+
+      context 'when root container repository does not exist' do
+        context 'when there are tags for this repository' do
+          before do
+            stub_container_registry_tags(%w[rc1 latest])
+          end
+
+          it 'successfully renders container repositories' do
+            go_to_index
+
+            expect(response).to have_http_status(:ok)
+          end
+
+          it 'creates a root container repository' do
+            expect { go_to_index }.to change { ContainerRepository.all.count }.by(1)
+            expect(ContainerRepository.first).to be_root_repository
+          end
+        end
+
+        context 'when there are no tags for this repository' do
+          before do
+            stub_container_registry_tags(*[])
+          end
+
+          it 'successfully renders container repositories' do
+            go_to_index
+
+            expect(response).to have_http_status(:ok)
+          end
+
+          it 'does not ensure root container repository' do
+            expect { go_to_index }.not_to change { ContainerRepository.all.count }
+          end
+        end
+      end
+    end
+  end
+
+  context 'when user does not have access to registry' do
+    describe 'GET index' do
+      it 'responds with 404' do
+        go_to_index
+
+        expect(response).to have_http_status(:not_found)
+      end
+
+      it 'does not ensure root container repository' do
+        expect { go_to_index }.not_to change { ContainerRepository.all.count }
+      end
+    end
+  end
+
+  def go_to_index
+    get :index, namespace_id: project.namespace,
+                project_id: project
+  end
+end

spec/factories/container_repositories.rb

@@ -7,6 +7,10 @@ FactoryGirl.define do
       tags []
     end
+    trait :root do
+      name ''
+    end
+
     after(:build) do |repository, evaluator|
       next if evaluator.tags.to_a.none?

spec/models/container_repository_spec.rb

@@ -98,6 +98,43 @@ describe ContainerRepository do
     end
   end
+  describe '#root_repository?' do
+    context 'when repository is a root repository' do
+      let(:repository) { create(:container_repository, :root) }
+
+      it 'returns true' do
+        expect(repository).to be_root_repository
+      end
+    end
+
+    context 'when repository is not a root repository' do
+      it 'returns false' do
+        expect(container_repository).not_to be_root_repository
+      end
+    end
+  end
+
+  describe '.build_from_path' do
+    let(:path) { project.full_path + '/some/image' }
+    let(:repository_path) { ContainerRegistry::Path.new(path) }
+
+    let(:repository) do
+      described_class.build_from_path(ContainerRegistry::Path.new(path))
+    end
+
+    it 'fabricates repository assigned to a correct project' do
+      expect(repository.project).to eq project
+    end
+
+    it 'fabricates repository with a correct name' do
+      expect(repository.name).to eq 'some/image'
+    end
+
+    it 'is not persisted' do
+      expect(repository).not_to be_persisted
+    end
+  end
+
   describe '.create_from_path!' do
     let(:repository) do
       described_class.create_from_path!(ContainerRegistry::Path.new(path))