1 files changed, 92 insertions, 0 deletions
diff --git a/tooling/danger/changelog.rb b/tooling/danger/changelog.rb
new file mode 100644
index 00000000000..f7f505f51a6
--- /dev/null
+++ b/tooling/danger/changelog.rb
@@ -0,0 +1,92 @@
+# frozen_string_literal: true
+
+require_relative 'title_linting'
+
+module Tooling
+  module Danger
+    module Changelog
+      NO_CHANGELOG_LABELS = [
+        'tooling',
+        'tooling::pipelines',
+        'tooling::workflow',
+        'ci-build',
+        'meta'
+      ].freeze
+      NO_CHANGELOG_CATEGORIES = %i[docs none].freeze
+      CREATE_CHANGELOG_COMMAND = 'bin/changelog -m %<mr_iid>s "%<mr_title>s"'
+      CREATE_EE_CHANGELOG_COMMAND = 'bin/changelog --ee -m %<mr_iid>s "%<mr_title>s"'
+      CHANGELOG_MODIFIED_URL_TEXT = "**CHANGELOG.md was edited.** Please remove the additions and create a CHANGELOG entry.\n\n"
+      CHANGELOG_MISSING_URL_TEXT = "**[CHANGELOG missing](https://docs.gitlab.com/ee/development/changelog.html)**:\n\n"
+
+      OPTIONAL_CHANGELOG_MESSAGE = <<~MSG
+      If you want to create a changelog entry for GitLab FOSS, run the following:
+
+          #{CREATE_CHANGELOG_COMMAND}
+
+      If you want to create a changelog entry for GitLab EE, run the following instead:
+
+          #{CREATE_EE_CHANGELOG_COMMAND}
+
+      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.
+      MSG
+
+      REQUIRED_CHANGELOG_MESSAGE = <<~MSG
+      To create a changelog entry, run the following:
+
+          #{CREATE_CHANGELOG_COMMAND}
+
+      This merge request requires a changelog entry because it [introduces a database migration](https://docs.gitlab.com/ee/development/changelog.html#what-warrants-a-changelog-entry).
+      MSG
+
+      def required?
+        git.added_files.any? { |path| path =~ %r{\Adb/(migrate|post_migrate)/} }
+      end
+      alias_method :db_changes?, :required?
+
+      def optional?
+        categories_need_changelog? && without_no_changelog_label?
+      end
+
+      def found
+        @found ||= git.added_files.find { |path| path =~ %r{\A(ee/)?(changelogs/unreleased)(-ee)?/} }
+      end
+
+      def ee_changelog?
+        found.start_with?('ee/')
+      end
+
+      def modified_text
+        CHANGELOG_MODIFIED_URL_TEXT +
+          format(OPTIONAL_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
+      def required_text
+        CHANGELOG_MISSING_URL_TEXT +
+          format(REQUIRED_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
+      def optional_text
+        CHANGELOG_MISSING_URL_TEXT +
+          format(OPTIONAL_CHANGELOG_MESSAGE, mr_iid: mr_iid, mr_title: sanitized_mr_title)
+      end
+
+      private
+
+      def mr_iid
+        gitlab.mr_json["iid"]
+      end
+
+      def sanitized_mr_title
+        TitleLinting.sanitize_mr_title(gitlab.mr_json["title"])
+      end
+
+      def categories_need_changelog?
+        (helper.changes_by_category.keys - NO_CHANGELOG_CATEGORIES).any?
+      end
+
+      def without_no_changelog_label?
+        (gitlab.mr_labels & NO_CHANGELOG_LABELS).empty?
+      end
+    end
+  end
+end