Add Danger message when ci templates are updated

Add specs for ci template check tooling

Fix the formatting and file path with changes.category method

Add check! spec and fix a bug in existing code

danger/ci_templates/Dangerfile

 # frozen_string_literal: true
 
-CI_CD_TEMPLATE_MESSAGE = <<~MSG
-This merge request requires a CI/CD Template review. To make sure these
-changes are reviewed, take the following steps:
-
-1. Ensure the merge request has the ~"ci::templates" label.
-   If the merge request modifies CI/CD Template files, Danger will do this for you.
-1. Prepare your MR for a CI/CD Template review according to the
-   [template development guide](https://docs.gitlab.com/ee/development/cicd/templates.html).
-1. Assign and `@` mention the CI/CD Template reviewer suggested by Reviewer Roulette.
-MSG
-
-CI_CD_TEMPLATE_FILES_MESSAGE = <<~MSG
-The following files require a review from the CI/CD Templates maintainers:
-MSG
-
-return unless helper.ci?
-
-template_paths_to_review = helper.changes_by_category[:ci_template]
-
-if helper.mr_labels.include?('ci::templates') || template_paths_to_review.any?
-  message('This merge request adds or changes files that require a ' \
-          'review from the CI/CD Templates maintainers.')
-
-  markdown(CI_CD_TEMPLATE_MESSAGE)
-
-  if template_paths_to_review.any?
-    markdown(CI_CD_TEMPLATE_FILES_MESSAGE + helper.markdown_list(template_paths_to_review))
-  end
-end
+ci_templates.check!

danger/plugins/ci_templates.rb

+# frozen_string_literal: true
+
+require_relative '../../tooling/danger/ci_templates'
+
+module Danger
+  class CiTemplates < ::Danger::Plugin
+    include Tooling::Danger::CiTemplates
+  end
+end

spec/tooling/danger/ci_templates_spec.rb

+# frozen_string_literal: true
+
+require 'gitlab/dangerfiles/spec_helper'
+require 'fast_spec_helper'
+require 'rspec-parameterized'
+
+require_relative '../../../danger/plugins/ci_templates'
+
+RSpec.describe Tooling::Danger::CiTemplates, feature_category: :tooling do
+  include_context 'with dangerfile'
+  subject(:ci_templates) { fake_danger.new(helper: fake_helper) }
+
+  let(:fake_danger) { DangerSpecHelper.fake_danger.include(described_class) }
+
+  before do
+    allow(fake_helper).to receive(:ci?).and_return(ci_env)
+  end
+
+  describe '#check!' do
+    context 'when not in ci environment' do
+      let(:ci_env) { false }
+
+      it 'does not add the warnings' do
+        expect(ci_templates).not_to receive(:message)
+        expect(ci_templates).not_to receive(:markdown)
+        expect(ci_templates).not_to receive(:warn)
+
+        ci_templates.check!
+      end
+    end
+
+    context 'when in ci environment' do
+      let(:ci_env) { true }
+      let(:modified_files) { %w[lib/gitlab/ci/templates/ci_template.rb] }
+      let(:fake_changes) { instance_double(Gitlab::Dangerfiles::Changes, files: modified_files) }
+
+      context 'when there are updates to the ci templates' do
+        before do
+          allow(fake_changes).to receive(:by_category).with(:ci_template).and_return(fake_changes)
+          allow(fake_helper).to receive(:changes).and_return(fake_changes)
+          allow(ci_templates).to receive(:message)
+          allow(ci_templates).to receive(:markdown)
+          allow(fake_helper).to receive(:markdown_list).and_return(modified_files)
+        end
+
+        it 'adds the danger message, markdown and warning' do
+          expect(ci_templates).to receive(:message)
+          expect(ci_templates).to receive(:markdown)
+          expect(ci_templates).to receive(:warn)
+
+          ci_templates.check!
+        end
+
+        context 'when there are files returned by markdown_list' do
+          it 'returns markdown message' do
+            expect(fake_helper).to receive(:markdown_list).with(modified_files)
+            expect(ci_templates).to receive(:markdown).with(/#{modified_files}/)
+
+            ci_templates.check!
+          end
+        end
+      end
+
+      context 'when there are no updated ci templates' do
+        it 'does not add the danger message, markdown and warning' do
+          expect(ci_templates).not_to receive(:message)
+          expect(ci_templates).not_to receive(:markdown)
+          expect(ci_templates).not_to receive(:warn)
+
+          ci_templates.check!
+        end
+      end
+    end
+  end
+end

tooling/danger/ci_templates.rb

+# frozen_string_literal: true
+
+module Tooling
+  module Danger
+    module CiTemplates
+      CI_CD_TEMPLATE_MESSAGE = <<~MSG
+        This merge request requires a CI/CD Template review. To make sure these
+        changes are reviewed, take the following steps:
+
+        1. Ensure the merge request has the ~"ci::templates" label.
+        If the merge request modifies CI/CD Template files, Danger will do this for you.
+        1. Prepare your MR for a CI/CD Template review according to the
+        [template development guide](https://docs.gitlab.com/ee/development/cicd/templates.html).
+        1. Assign and `@` mention the CI/CD Template reviewer suggested by Reviewer Roulette.
+      MSG
+
+      CI_CD_TEMPLATE_MODIFIED_WARNING = <<~MSG
+        This merge request adds or changes templates, please consider updating the corresponding
+        [Gitlab Component](https://gitlab.com/components).
+      MSG
+
+      def check!
+        return unless helper.ci?
+
+        return unless helper.mr_labels.include?('ci::templates') || changes.any?
+
+        message('This merge request adds or changes files that require a ' \
+                'review from the CI/CD Templates maintainers.')
+
+        markdown(CI_CD_TEMPLATE_MESSAGE)
+
+        return unless changes.any?
+
+        markdown(<<~MSG
+              The following files require a review from the CI/CD Templates maintainers:
+              #{helper.markdown_list(changes)}
+        MSG
+                )
+        warn(CI_CD_TEMPLATE_MODIFIED_WARNING)
+      end
+
+      private
+
+      def changes
+        helper.changes.by_category(:ci_template).files
+      end
+    end
+  end
+end