Create changelog plugin

- Moved helper methods from Dangerfile into a new Danger plugin
- Added tests for all public methods in the plugin

Dangerfile

@@ -5,6 +5,7 @@ require_relative 'lib/gitlab/danger/request_helper'
 
 danger.import_plugin('danger/plugins/helper.rb')
 danger.import_plugin('danger/plugins/roulette.rb')
+danger.import_plugin('danger/plugins/changelog.rb')
 
 unless helper.release_automation?
   GitlabDanger.new(helper.gitlab_helper).rule_names.each do |file|

danger/changelog/Dangerfile

@@ -3,7 +3,6 @@
 
 require 'yaml'
 
-NO_CHANGELOG_LABELS = %w[backstage ci-build meta].freeze
 SEE_DOC = "See [the documentation](https://docs.gitlab.com/ce/development/changelog.html)."
 CREATE_CHANGELOG_MESSAGE = <<~MSG
 You can create one with:
@@ -21,18 +20,6 @@ bin/changelog --ee -m %<mr_iid>s "%<mr_title>s"
 Note: Merge requests with %<labels>s do not trigger this check.
 MSG
 
-def ee_changelog?(changelog_path)
-  changelog_path =~ /unreleased-ee/
-end
-
-def ce_port_changelog?(changelog_path)
-  helper.ee? && !ee_changelog?(changelog_path)
-end
-
-def categories_need_changelog?
-  (helper.changes_by_category.keys - %i[docs none]).any?
-end
-
 def check_changelog(path)
   yaml = YAML.safe_load(File.read(path))
 
@@ -41,7 +28,7 @@ def check_changelog(path)
 
   if yaml["merge_request"].nil?
     message "Consider setting `merge_request` to #{gitlab.mr_json["iid"]} in #{gitlab.html_link(path)}. #{SEE_DOC}"
-  elsif yaml["merge_request"] != gitlab.mr_json["iid"] && !ce_port_changelog?(path)
+  elsif yaml["merge_request"] != gitlab.mr_json["iid"] && !changelog.ce_port_changelog?(path)
     fail "Merge request ID was not set to #{gitlab.mr_json["iid"]}! #{SEE_DOC}"
   end
 rescue Psych::SyntaxError, Psych::DisallowedClass, Psych::BadAlias
@@ -51,27 +38,18 @@ rescue StandardError => e
   warn "There was a problem trying to check the Changelog. Exception: #{e.name} - #{e.message}"
 end
 
-def presented_no_changelog_labels
-  NO_CHANGELOG_LABELS.map { |label| "~#{label}" }.join(', ')
-end
-
-def sanitized_mr_title
-  gitlab.mr_json["title"].gsub(/^WIP: */, '').gsub(/`/, '\\\`')
-end
-
-changelog_needed = categories_need_changelog? && (gitlab.mr_labels & NO_CHANGELOG_LABELS).empty?
-changelog_found = git.added_files.find { |path| path =~ %r{\A(ee/)?(changelogs/unreleased)(-ee)?/} }
-
 if git.modified_files.include?("CHANGELOG.md")
   fail "**CHANGELOG.md was edited.** Please remove the additions and create a CHANGELOG entry.\n\n" +
-    format(CREATE_CHANGELOG_MESSAGE, mr_iid: gitlab.mr_json["iid"], mr_title: sanitized_mr_title, labels: presented_no_changelog_labels)
+    format(CREATE_CHANGELOG_MESSAGE, mr_iid: gitlab.mr_json["iid"], mr_title: changelog.sanitized_mr_title, labels: changelog.presented_no_changelog_labels)
 end
 
-if changelog_needed
+changelog_found = changelog.found
+
+if changelog.needed?
   if changelog_found
     check_changelog(changelog_found)
   else
     message "**[CHANGELOG missing](https://docs.gitlab.com/ce/development/changelog.html)**: If this merge request [doesn't need a CHANGELOG entry](https://docs.gitlab.com/ee/development/changelog.html#what-warrants-a-changelog-entry), feel free to ignore this message.\n\n" +
-      format(CREATE_CHANGELOG_MESSAGE, mr_iid: gitlab.mr_json["iid"], mr_title: sanitized_mr_title, labels: presented_no_changelog_labels)
+      format(CREATE_CHANGELOG_MESSAGE, mr_iid: gitlab.mr_json["iid"], mr_title: changelog.sanitized_mr_title, labels: changelog.presented_no_changelog_labels)
   end
 end

danger/plugins/changelog.rb

+# frozen_string_literal: true
+
+require_relative '../../lib/gitlab/danger/changelog'
+
+module Danger
+  class Changelog < Plugin
+    # Put the helper code somewhere it can be tested
+    include Gitlab::Danger::Changelog
+  end
+end

lib/gitlab/danger/changelog.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Danger
+    module Changelog
+      NO_CHANGELOG_LABELS = %w[backstage ci-build meta].freeze
+      NO_CHANGELOG_CATEGORIES = %i[docs none].freeze
+
+      def needed?
+        categories_need_changelog? && (gitlab.mr_labels & NO_CHANGELOG_LABELS).empty?
+      end
+
+      def found
+        git.added_files.find { |path| path =~ %r{\A(ee/)?(changelogs/unreleased)(-ee)?/} }
+      end
+
+      def presented_no_changelog_labels
+        NO_CHANGELOG_LABELS.map { |label| "~#{label}" }.join(', ')
+      end
+
+      def sanitized_mr_title
+        gitlab.mr_json["title"].gsub(/^WIP: */, '').gsub(/`/, '\\\`')
+      end
+
+      def ee_changelog?(changelog_path)
+        changelog_path =~ /unreleased-ee/
+      end
+
+      def ce_port_changelog?(changelog_path)
+        helper.ee? && !ee_changelog?(changelog_path)
+      end
+
+      private
+
+      def categories_need_changelog?
+        (helper.changes_by_category.keys - NO_CHANGELOG_CATEGORIES).any?
+      end
+    end
+  end
+end

spec/lib/gitlab/danger/changelog_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require 'rspec-parameterized'
+require_relative 'danger_spec_helper'
+
+require 'gitlab/danger/changelog'
+
+describe Gitlab::Danger::Changelog do
+  using RSpec::Parameterized::TableSyntax
+  include DangerSpecHelper
+
+  let(:added_files) { nil }
+  let(:fake_git) { double('fake-git', added_files: added_files) }
+
+  let(:mr_labels) { nil }
+  let(:mr_json) { nil }
+  let(:fake_gitlab) { double('fake-gitlab', mr_labels: mr_labels, mr_json: mr_json) }
+
+  let(:changes_by_category) { nil }
+  let(:ee?) { false }
+  let(:fake_helper) { double('fake-helper', changes_by_category: changes_by_category, ee?: ee?) }
+
+  let(:fake_danger) { new_fake_danger.include(described_class) }
+
+  subject(:changelog) { fake_danger.new(git: fake_git, gitlab: fake_gitlab, helper: fake_helper) }
+
+  describe '#needed?' do
+    subject { changelog.needed? }
+
+    [
+      { docs: nil },
+      { none: nil },
+      { docs: nil, none: nil }
+    ].each do |categories|
+      let(:changes_by_category) { categories }
+      it "is falsy when categories don't require a changelog" do
+        is_expected.to be_falsy
+      end
+    end
+
+    where(:categories, :labels) do
+      { backend: nil }                             | %w[backend backstage]
+      { frontend: nil, docs: nil }                 | ['ci-build']
+      { engineering_productivity: nil, none: nil } | ['meta']
+    end
+
+    with_them do
+      let(:changes_by_category) { categories }
+      let(:mr_labels) { labels }
+
+      it "is falsy when labels require no changelog" do
+        is_expected.to be_falsy
+      end
+    end
+
+    where(:categories, :labels) do
+      { frontend: nil, docs: nil }                 | ['database::review pending', 'feature']
+      { backend: nil }                             | ['backend', 'technical debt']
+      { engineering_productivity: nil, none: nil } | ['frontend']
+    end
+
+    with_them do
+      let(:changes_by_category) { categories }
+      let(:mr_labels) { labels }
+
+      it "is truthy when categories and labels require a changelog" do
+        is_expected.to be_truthy
+      end
+    end
+  end
+
+  describe '#found' do
+    subject { changelog.found }
+
+    context 'added files contain a changelog' do
+      [
+        'changelogs/unreleased/entry.md',
+        'ee/changelogs/unreleased/entry.md',
+        'changelogs/unreleased-ee/entry.md',
+        'ee/changelogs/unreleased-ee/entry.md'
+      ].each do |file_path|
+        let(:added_files) { [file_path] }
+
+        it { is_expected.to be_truthy }
+      end
+    end
+
+    context 'added files do not contain a changelog' do
+      [
+        'app/models/model.rb',
+        'app/assets/javascripts/file.js'
+      ].each do |file_path|
+        let(:added_files) { [file_path] }
+        it { is_expected.to eq(nil) }
+      end
+    end
+  end
+
+  describe '#presented_no_changelog_labels' do
+    subject { changelog.presented_no_changelog_labels }
+
+    it 'returns the labels formatted' do
+      is_expected.to eq('~backstage, ~ci-build, ~meta')
+    end
+  end
+
+  describe '#sanitized_mr_title' do
+    subject { changelog.sanitized_mr_title }
+
+    [
+      'WIP: My MR title',
+      'My MR title'
+    ].each do |mr_title|
+      let(:mr_json) { { "title" => mr_title } }
+      it { is_expected.to eq("My MR title") }
+    end
+  end
+
+  describe '#ee_changelog?' do
+    context 'is ee changelog' do
+      [
+        'changelogs/unreleased-ee/entry.md',
+        'ee/changelogs/unreleased-ee/entry.md'
+      ].each do |file_path|
+        subject { changelog.ee_changelog?(file_path) }
+
+        it { is_expected.to be_truthy }
+      end
+    end
+
+    context 'is not ee changelog' do
+      [
+        'changelogs/unreleased/entry.md',
+        'ee/changelogs/unreleased/entry.md'
+      ].each do |file_path|
+        subject { changelog.ee_changelog?(file_path) }
+
+        it { is_expected.to be_falsy }
+      end
+    end
+  end
+
+  describe '#ce_port_changelog?' do
+    where(:helper_ee?, :file_path, :expected) do
+      true  | 'changelogs/unreleased-ee/entry.md'    | false
+      true  | 'ee/changelogs/unreleased-ee/entry.md' | false
+      false | 'changelogs/unreleased-ee/entry.md'    | false
+      false | 'ee/changelogs/unreleased-ee/entry.md' | false
+      true  | 'changelogs/unreleased/entry.md'       | true
+      true  | 'ee/changelogs/unreleased/entry.md'    | true
+      false | 'changelogs/unreleased/entry.md'       | false
+      false | 'ee/changelogs/unreleased/entry.md'    | false
+    end
+
+    with_them do
+      let(:ee?) { helper_ee? }
+      subject { changelog.ce_port_changelog?(file_path) }
+
+      it { is_expected.to eq(expected) }
+    end
+  end
+end

spec/lib/gitlab/danger/danger_spec_helper.rb

+# frozen_string_literal: true
+
+module DangerSpecHelper
+  def new_fake_danger
+    Class.new do
+      attr_reader :git, :gitlab, :helper
+
+      # rubocop:disable Gitlab/ModuleWithInstanceVariables
+      def initialize(git: nil, gitlab: nil, helper: nil)
+        @git = git
+        @gitlab = gitlab
+        @helper = helper
+      end
+      # rubocop:enable Gitlab/ModuleWithInstanceVariables
+    end
+  end
+end

spec/lib/gitlab/danger/helper_spec.rb

@@ -2,29 +2,22 @@
 
 require 'fast_spec_helper'
 require 'rspec-parameterized'
+require_relative 'danger_spec_helper'
 
 require 'gitlab/danger/helper'
 
 describe Gitlab::Danger::Helper do
   using RSpec::Parameterized::TableSyntax
-
-  class FakeDanger
-    include Gitlab::Danger::Helper
-
-    attr_reader :git, :gitlab
-
-    def initialize(git:, gitlab:)
-      @git = git
-      @gitlab = gitlab
-    end
-  end
+  include DangerSpecHelper
 
   let(:fake_git) { double('fake-git') }
 
   let(:mr_author) { nil }
   let(:fake_gitlab) { double('fake-gitlab', mr_author: mr_author) }
 
-  subject(:helper) { FakeDanger.new(git: fake_git, gitlab: fake_gitlab) }
+  let(:fake_danger) { new_fake_danger.include(described_class) }
+
+  subject(:helper) { fake_danger.new(git: fake_git, gitlab: fake_gitlab) }
 
   describe '#gitlab_helper' do
     context 'when gitlab helper is not available' do