Show expanded YAML when linting CI config via API

Show YAML with includes and extend entries expanded.

lib/api/lint.rb

@@ -6,18 +6,23 @@ module API
       desc 'Validation of .gitlab-ci.yml content'
       params do
         requires :content, type: String, desc: 'Content of .gitlab-ci.yml'
+        optional :include_merged_yaml, type: Boolean, desc: 'Whether or not to include merged CI config yaml in the response'
       end
       post '/lint' do
-        error = Gitlab::Ci::YamlProcessor.validation_message(params[:content],
-          user: current_user)
+        result = Gitlab::Ci::YamlProcessor.new(params[:content], user: current_user).execute
+        error = result.errors.first
 
         status 200
 
-        if error.blank?
+        response = if error.blank?
                      { status: 'valid', errors: [] }
                    else
                      { status: 'invalid', errors: [error] }
                    end
+
+        response.tap do |response|
+          response[:merged_yaml] = result.merged_yaml if params[:include_merged_yaml]
+        end
       end
     end
   end

lib/gitlab/ci/yaml_processor/result.rb

@@ -95,6 +95,10 @@ module Gitlab
             }.compact }.compact
         end
 
+        def merged_yaml
+          @ci_config&.to_hash&.to_yaml
+        end
+
         private
 
         def variables

spec/lib/gitlab/ci/yaml_processor/result_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+module Gitlab
+  module Ci
+    class YamlProcessor
+      RSpec.describe Result do
+        include StubRequests
+
+        let(:user) { create(:user) }
+        let(:ci_config) { Gitlab::Ci::Config.new(config_content, user: user) }
+        let(:result) { described_class.new(ci_config: ci_config, warnings: ci_config&.warnings) }
+
+        describe '#merged_yaml' do
+          subject(:merged_yaml) { result.merged_yaml }
+
+          let(:config_content) do
+            YAML.dump(
+              include: { remote: 'https://example.com/sample.yml' },
+              test: { stage: 'test', script: 'echo' }
+            )
+          end
+
+          let(:included_yml) do
+            YAML.dump(
+              another_test: { stage: 'test', script: 'echo 2' }
+            )
+          end
+
+          before do
+            stub_full_request('https://example.com/sample.yml').to_return(body: included_yml)
+          end
+
+          it 'returns expanded yaml config' do
+            expanded_config = YAML.safe_load(merged_yaml, [Symbol])
+            included_config = YAML.safe_load(included_yml, [Symbol])
+
+            expect(expanded_config).to include(*included_config.keys)
+          end
+        end
+      end
+    end
+  end
+end

spec/requests/api/lint_spec.rb

@@ -17,24 +17,53 @@ RSpec.describe API::Lint do
         expect(json_response['status']).to eq('valid')
         expect(json_response['errors']).to eq([])
       end
+
+      it 'outputs expanded yaml content' do
+        post api('/ci/lint'), params: { content: yaml_content, include_merged_yaml: true }
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response).to have_key('merged_yaml')
+      end
     end
 
     context 'with an invalid .gitlab_ci.yml' do
+      context 'with invalid syntax' do
+        let(:yaml_content) { 'invalid content' }
+
         it 'responds with errors about invalid syntax' do
-        post api('/ci/lint'), params: { content: 'invalid content' }
+          post api('/ci/lint'), params: { content: yaml_content }
 
           expect(response).to have_gitlab_http_status(:ok)
           expect(json_response['status']).to eq('invalid')
           expect(json_response['errors']).to eq(['Invalid configuration format'])
         end
 
-      it "responds with errors about invalid configuration" do
-        post api('/ci/lint'), params: { content: '{ image: "ruby:2.7",  services: ["postgres"] }' }
+        it 'outputs expanded yaml content' do
+          post api('/ci/lint'), params: { content: yaml_content, include_merged_yaml: true }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(json_response).to have_key('merged_yaml')
+        end
+      end
+
+      context 'with invalid configuration' do
+        let(:yaml_content) { '{ image: "ruby:2.7",  services: ["postgres"] }' }
+
+        it 'responds with errors about invalid configuration' do
+          post api('/ci/lint'), params: { content: yaml_content }
 
           expect(response).to have_gitlab_http_status(:ok)
           expect(json_response['status']).to eq('invalid')
           expect(json_response['errors']).to eq(['jobs config should contain at least one visible job'])
         end
+
+        it 'outputs expanded yaml content' do
+          post api('/ci/lint'), params: { content: yaml_content, include_merged_yaml: true }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(json_response).to have_key('merged_yaml')
+        end
+      end
     end
 
     context 'without the content parameter' do