Add new GitlabDanger class

This class encapsulates our use of the Danger gem.

3 files changed, 81 insertions, 1 deletions

diff --git a/lib/gitlab/danger/helper.rb b/lib/gitlab/danger/helper.rb
index 17ad07bfc0c..e2911b4e6c8 100644
--- a/lib/gitlab/danger/helper.rb
+++ b/lib/gitlab/danger/helper.rb
@@ -38,8 +38,17 @@ module Gitlab
         ENV['CI_PROJECT_NAME'] == 'gitlab-ee' || File.exist?('../../CHANGELOG-EE.md')
       end
 
+      def gitlab_helper
+        # Unfortunately the following does not work:
+        # - respond_to?(:gitlab)
+        # - respond_to?(:gitlab, true)
+        gitlab
+      rescue NoMethodError
+        nil
+      end
+
       def release_automation?
-        gitlab.mr_author == RELEASE_TOOLS_BOT
+        gitlab_helper&.mr_author == RELEASE_TOOLS_BOT
       end
 
       def project_name
diff --git a/lib/gitlab_danger.rb b/lib/gitlab_danger.rb
new file mode 100644
index 00000000000..b4768a9546d
--- /dev/null
+++ b/lib/gitlab_danger.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+class GitlabDanger
+  LOCAL_RULES ||= %w[
+    changes_size
+    gemfile
+    documentation
+    frozen_string
+    duplicate_yarn_dependencies
+    prettier
+    eslint
+    database
+  ].freeze
+
+  CI_ONLY_RULES ||= %w[
+    metadata
+    changelog
+    specs
+    commit_messages
+    roulette
+    single_codebase
+    gitlab_ui_wg
+    ce_ee_vue_templates
+    only_documentation
+  ].freeze
+
+  MESSAGE_PREFIX = '==>'.freeze
+
+  attr_reader :gitlab_danger_helper
+
+  def initialize(gitlab_danger_helper)
+    @gitlab_danger_helper = gitlab_danger_helper
+  end
+
+  def self.local_warning_message
+    "#{MESSAGE_PREFIX} Only the following Danger rules can be run locally: #{LOCAL_RULES.join(', ')}"
+  end
+
+  def self.success_message
+    "#{MESSAGE_PREFIX} No Danger rule violations!"
+  end
+
+  def rule_names
+    ci? ? LOCAL_RULES | CI_ONLY_RULES : LOCAL_RULES
+  end
+
+  def html_link(str)
+    self.ci? ? gitlab_danger_helper.html_link(str) : str
+  end
+
+  def ci?
+    !gitlab_danger_helper.nil?
+  end
+end
diff --git a/lib/tasks/gitlab_danger.rake b/lib/tasks/gitlab_danger.rake
new file mode 100644
index 00000000000..e75539f048c
--- /dev/null
+++ b/lib/tasks/gitlab_danger.rake
@@ -0,0 +1,17 @@
+desc 'Run local Danger rules'
+task :danger_local do
+  require 'gitlab_danger'
+  require 'gitlab/popen'
+
+  puts("#{GitlabDanger.local_warning_message}\n")
+
+  # _status will _always_ be 0, regardless of failure or success :(
+  output, _status = Gitlab::Popen.popen(%w{danger dry_run})
+
+  if output.empty?
+    puts(GitlabDanger.success_message)
+  else
+    puts(output)
+    exit(1)
+  end
+end