Cop for database migration class

rubocop/cop/migration/versioned_migration_class.rb

+# frozen_string_literal: true
+
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      class VersionedMigrationClass < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        ENFORCED_SINCE = 2021_08_30_00_00_00
+
+        MSG_INHERIT = 'Don\'t inherit from ActiveRecord::Migration but use Gitlab::Database::Migration[1.0] instead.'
+        MSG_INCLUDE = 'Don\'t include migration helper modules directly. Inherit from Gitlab::Database::Migration[1.0] instead.'
+
+        MIGRATION_CLASS = 'Gitlab::Database::Migration'
+
+        def_node_search :includes_helpers?, <<~PATTERN
+        (send nil? :include
+          (const
+            (const
+              (const nil? :Gitlab) :Database) :MigrationHelpers))
+        PATTERN
+
+        def on_class(node)
+          return unless relevant_migration?(node)
+
+          add_offense(node, location: :expression, message: MSG_INHERIT) unless gitlab_migration_class?(node)
+        end
+
+        def on_send(node)
+          return unless relevant_migration?(node)
+
+          add_offense(node, location: :expression, message: MSG_INCLUDE) if includes_helpers?(node)
+        end
+
+        private
+
+        def relevant_migration?(node)
+          in_migration?(node) && version(node) >= ENFORCED_SINCE
+        end
+
+        def gitlab_migration_class?(node)
+          superclass(node) == MIGRATION_CLASS
+        end
+
+        def superclass(class_node)
+          _, *others = class_node.descendants
+
+          others.find { |node| node.const_type? && node&.const_name != 'Types' }&.const_name
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/migration/versioned_migration_class_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require_relative '../../../../rubocop/cop/migration/versioned_migration_class'
+
+RSpec.describe RuboCop::Cop::Migration::VersionedMigrationClass do
+  subject(:cop) { described_class.new }
+
+  let(:migration) do
+    <<~SOURCE
+      class TestMigration < Gitlab::Database::Migration[1.0]
+        def up
+          execute 'select 1'
+        end
+
+        def down
+          execute 'select 1'
+        end
+      end
+    SOURCE
+  end
+
+  shared_examples 'a disabled cop' do
+    it 'does not register any offenses' do
+      expect_no_offenses(migration)
+    end
+  end
+
+  context 'outside of a migration' do
+    it_behaves_like 'a disabled cop'
+  end
+
+  context 'in migration' do
+    before do
+      allow(cop).to receive(:in_migration?).and_return(true)
+    end
+
+    context 'in an old migration' do
+      before do
+        allow(cop).to receive(:version).and_return(described_class::ENFORCED_SINCE - 5)
+      end
+
+      it_behaves_like 'a disabled cop'
+    end
+
+    context 'that is recent' do
+      before do
+        allow(cop).to receive(:version).and_return(described_class::ENFORCED_SINCE + 5)
+      end
+
+      it 'adds an offence if inheriting from ActiveRecord::Migration' do
+        expect_offense(<<~RUBY)
+          class MyMigration < ActiveRecord::Migration[6.1]
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't inherit from ActiveRecord::Migration but use Gitlab::Database::Migration[1.0] instead.
+          end
+        RUBY
+      end
+
+      it 'adds an offence if including Gitlab::Database::MigrationHelpers directly' do
+        expect_offense(<<~RUBY)
+          class MyMigration < Gitlab::Database::Migration[1.0]
+            include Gitlab::Database::MigrationHelpers
+            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Don't include migration helper modules directly. Inherit from Gitlab::Database::Migration[1.0] instead.
+          end
+        RUBY
+      end
+    end
+  end
+end