Add support for `extends` key in CI/CD configuration

lib/gitlab/ci/config.rb

@@ -4,12 +4,17 @@ module Gitlab
     # Base GitLab CI Configuration facade
     #
     class Config
-      # EE would override this and utilize opts argument
+      ConfigError = Class.new(StandardError)
+
       def initialize(config, opts = {})
-        @config = Loader.new(config).load!
+        @config = Extendable::Collection
+          .new(build_config(config, opts))
+          .to_hash
 
         @global = Entry::Global.new(@config)
         @global.compose!
+      rescue Loader::FormatError, Extendable::Collection::ExtensionError => e
+        raise Config::ConfigError, e.message
       end
 
       def valid?
@@ -58,6 +63,11 @@ module Gitlab
       def jobs
         @global.jobs_value
       end
+
+      # 'opts' argument is used in EE see /ee/lib/ee/gitlab/ci/config.rb
+      def build_config(config, opts = {})
+        Loader.new(config).load!
+      end
     end
   end
 end

lib/gitlab/ci/config/entry/job.rb

@@ -9,9 +9,10 @@ module Gitlab
           include Configurable
           include Attributable
 
-          ALLOWED_KEYS = %i[tags script only except type image services allow_failure
-                            type stage when artifacts cache dependencies before_script
-                            after_script variables environment coverage retry].freeze
+          ALLOWED_KEYS = %i[tags script only except type image services
+                            allow_failure type stage when artifacts cache
+                            dependencies before_script after_script variables
+                            environment coverage retry extends].freeze
 
           validations do
             validates :config, allowed_keys: ALLOWED_KEYS
@@ -32,6 +33,7 @@ module Gitlab
                                       'always or manual' }
 
               validates :dependencies, array_of_strings: true
+              validates :extends, type: String
             end
           end
 
@@ -81,7 +83,8 @@ module Gitlab
                   :cache, :image, :services, :only, :except, :variables,
                   :artifacts, :commands, :environment, :coverage, :retry
 
-          attributes :script, :tags, :allow_failure, :when, :dependencies, :retry
+          attributes :script, :tags, :allow_failure, :when, :dependencies,
+                     :retry, :extends
 
           def compose!(deps = nil)
             super do

lib/gitlab/ci/yaml_processor.rb

@@ -16,7 +16,7 @@ module Gitlab
         end
 
         initial_parsing
-      rescue Gitlab::Ci::Config::Loader::FormatError => e
+      rescue Gitlab::Ci::Config::ConfigError => e
         raise ValidationError, e.message
       end
 

spec/lib/gitlab/ci/config_spec.rb

-require 'spec_helper'
+require 'fast_spec_helper'
+
+require_dependency 'active_model'
 
 describe Gitlab::Ci::Config do
   let(:config) do
@@ -42,6 +44,36 @@ describe Gitlab::Ci::Config do
     end
   end
 
+  context 'when using extendable hash' do
+    let(:yml) do
+      <<-EOS
+        image: ruby:2.2
+
+        rspec:
+          script: rspec
+
+        test:
+          extends: rspec
+          image: ruby:alpine
+      EOS
+    end
+
+    it 'correctly extends the hash' do
+      hash = {
+        image: 'ruby:2.2',
+        rspec: { script: 'rspec' },
+        test: {
+          extends: 'rspec',
+          image: 'ruby:alpine',
+          script: 'rspec'
+        }
+      }
+
+      expect(config).to be_valid
+      expect(config.to_hash).to eq hash
+    end
+  end
+
   context 'when config is invalid' do
     context 'when yml is incorrect' do
       let(:yml) { '// invalid' }
@@ -49,7 +81,7 @@ describe Gitlab::Ci::Config do
       describe '.new' do
         it 'raises error' do
           expect { config }.to raise_error(
-            ::Gitlab::Ci::Config::Loader::FormatError,
+            described_class::ConfigError,
             /Invalid configuration format/
           )
         end