Improve predefined variables collection methods

app/models/project.rb

@@ -1588,17 +1588,16 @@ class Project < ActiveRecord::Base
   def predefined_variables
     visibility = Gitlab::VisibilityLevel.string_level(visibility_level)
 
-    Gitlab::Ci::Variables::Collection.new.tap do |variables|
-      variables.append(key: 'CI_PROJECT_ID', value: id.to_s)
-      variables.append(key: 'CI_PROJECT_NAME', value: path)
-      variables.append(key: 'CI_PROJECT_PATH', value: full_path)
-      variables.append(key: 'CI_PROJECT_PATH_SLUG', value: full_path_slug)
-      variables.append(key: 'CI_PROJECT_NAMESPACE', value: namespace.full_path)
-      variables.append(key: 'CI_PROJECT_URL', value: web_url)
-      variables.append(key: 'CI_PROJECT_VISIBILITY', value: visibility)
-      variables.concat(container_registry_variables)
-      variables.concat(auto_devops_variables)
-    end
+    Gitlab::Ci::Variables::Collection.new
+      .append(key: 'CI_PROJECT_ID', value: id.to_s)
+      .append(key: 'CI_PROJECT_NAME', value: path)
+      .append(key: 'CI_PROJECT_PATH', value: full_path)
+      .append(key: 'CI_PROJECT_PATH_SLUG', value: full_path_slug)
+      .append(key: 'CI_PROJECT_NAMESPACE', value: namespace.full_path)
+      .append(key: 'CI_PROJECT_URL', value: web_url)
+      .append(key: 'CI_PROJECT_VISIBILITY', value: visibility)
+      .concat(container_registry_variables)
+      .concat(auto_devops_variables)
   end
 
   def container_registry_variables

lib/gitlab/ci/variables/collection.rb

@@ -11,11 +11,11 @@ module Gitlab
         end
 
         def append(resource)
-          @variables.append(Collection::Item.fabricate(resource))
+          tap { @variables.append(Collection::Item.fabricate(resource)) }
         end
 
         def concat(resources)
-          resources.each { |variable| self.append(variable) }
+          tap { resources.each { |variable| self.append(variable) } }
         end
 
         def each

spec/lib/gitlab/ci/variables/collection_spec.rb

@@ -35,6 +35,11 @@ describe Gitlab::Ci::Variables::Collection do
 
       expect(subject).to be_one
     end
+
+    it 'returns self' do
+      expect(subject.append(key: 'VAR', value: 'test'))
+        .to eq subject
+    end
   end
 
   describe '#concat' do
@@ -60,6 +65,11 @@ describe Gitlab::Ci::Variables::Collection do
       expect(collection).to include(key: 'VAR_2', value: '2', public: true)
       expect(collection).to include(key: 'VAR_3', value: '3', public: true)
     end
+
+    it 'returns self' do
+      expect(subject.concat([key: 'VAR', value: 'test']))
+        .to eq subject
+    end
   end
 
   describe '#+' do