Make it possible to define CI/CD config strategies

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

@@ -5,11 +5,28 @@ module Gitlab
         ##
         # Entry that represents a trigger policy for the job.
         #
-        class Policy < Node
-          include Validatable
+        class Policy < Simplifiable
+          strategy :RefsPolicy, if: -> (config) { config.is_a?(Array) }
+          strategy :ExpressionsPolicy, if: -> (config) { config.is_a?(Hash) }
 
-          validations do
-            validates :config, array_of_strings_or_regexps: true
+          class RefsPolicy < Entry::Node
+            include Entry::Validatable
+
+            validations do
+              validates :config, array_of_strings_or_regexps: true
+            end
+
+            def value
+              { refs: @config }
+            end
+          end
+
+          class ExpressionsPolicy < Entry::Node
+            include Entry::Validatable
+
+            validations do
+              validates :config, type: Hash
+            end
           end
         end
       end

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

+module Gitlab
+  module Ci
+    class Config
+      module Entry
+        class Simplifiable < SimpleDelegator
+          EntryStrategy = Struct.new(:name, :condition)
+
+          def initialize(config, **metadata)
+            strategy = self.class.strategies.find do |variant|
+              variant.condition.call(config)
+            end
+
+            entry = self.class.const_get(strategy.name)
+
+            super(entry.new(config, metadata))
+          end
+
+          def self.strategy(name, **opts)
+            EntryStrategy.new(name, opts.fetch(:if)).tap do |strategy|
+              (@strategies ||= []).append(strategy)
+            end
+          end
+
+          def self.strategies
+            @strategies || []
+          end
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/ci/config/entry/policy_spec.rb

@@ -3,54 +3,59 @@ require 'spec_helper'
 describe Gitlab::Ci::Config::Entry::Policy do
   let(:entry) { described_class.new(config) }
 
-  describe 'validations' do
-    context 'when entry config value is valid' do
-      context 'when config is a branch or tag name' do
-        let(:config) { %w[master feature/branch] }
-
-        describe '#valid?' do
-          it 'is valid' do
-            expect(entry).to be_valid
+  context 'when using simplified policy' do
+    describe 'validations' do
+      context 'when entry config value is valid' do
+        context 'when config is a branch or tag name' do
+          let(:config) { %w[master feature/branch] }
+
+          describe '#valid?' do
+            it 'is valid' do
+              expect(entry).to be_valid
+            end
           end
-        end
 
-        describe '#value' do
-          it 'returns key value' do
-            expect(entry.value).to eq config
+          describe '#value' do
+            it 'returns key value' do
+              expect(entry.value).to eq(refs: config)
+            end
           end
         end
-      end
 
-      context 'when config is a regexp' do
-        let(:config) { ['/^issue-.*$/'] }
+        context 'when config is a regexp' do
+          let(:config) { ['/^issue-.*$/'] }
 
-        describe '#valid?' do
-          it 'is valid' do
-            expect(entry).to be_valid
+          describe '#valid?' do
+            it 'is valid' do
+              expect(entry).to be_valid
+            end
           end
         end
-      end
 
-      context 'when config is a special keyword' do
-        let(:config) { %w[tags triggers branches] }
+        context 'when config is a special keyword' do
+          let(:config) { %w[tags triggers branches] }
 
-        describe '#valid?' do
-          it 'is valid' do
-            expect(entry).to be_valid
+          describe '#valid?' do
+            it 'is valid' do
+              expect(entry).to be_valid
+            end
           end
         end
       end
-    end
 
-    context 'when entry value is not valid' do
-      let(:config) { [1] }
+      context 'when entry value is not valid' do
+        let(:config) { [1] }
 
-      describe '#errors' do
-        it 'saves errors' do
-          expect(entry.errors)
-            .to include 'policy config should be an array of strings or regexps'
+        describe '#errors' do
+          it 'saves errors' do
+            expect(entry.errors)
+              .to include /policy config should be an array of strings or regexps/
+          end
         end
       end
     end
   end
+
+  context 'when using complex policy' do
+  end
 end