Add new MigrationFileName cop

changelog/new_add_new_migrationfilename_cop.md

@@ -0,0 +1 @@
+* [#644](https://github.com/rubocop/rubocop-rails/pull/644): Add new `MigrationFileName` cop. ([@johnny-miyake][])

config/default.yml

@@ -527,6 +527,13 @@ Rails/MatchRoute:
     - config/routes.rb
     - config/routes/**/*.rb
 
+Rails/MigrationFileName:
+  Description: 'The class name of the migration should match its file name.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+  Include:
+    - db/migrate/*.rb
+
 Rails/NegateInclude:
   Description: 'Prefer `collection.exclude?(obj)` over `!collection.include?(obj)`.'
   StyleGuide: 'https://rails.rubystyle.guide#exclude'

lib/rubocop/cop/rails/migration_file_name.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # This cop makes sure that each migration file defines a migration class
+      # whose name matches the file name.
+      # (i.e. `20220224111111_create_users.rb` should define `CreateUsers` class.)
+      #
+      # @example
+      #   # db/migrate/20220224111111_create_users.rb
+      #
+      #   # bad
+      #
+      #   class SellBooks < ActiveRecord::Migration[7.0]
+      #   end
+      #
+      #   # good
+      #
+      #   class CreateUsers < ActiveRecord::Migration[7.0]
+      #   end
+      #
+      class MigrationFileName < Base
+        MSG = 'The class name does not match with the file name.'
+
+        def on_new_investigation
+          filepath = processed_source.file_path
+          @basename = File.basename(filepath, '.rb')
+        end
+
+        def on_class(node)
+          class_name = node.loc.name.source
+          snake_class_name = to_snakecase(class_name)
+          basename_without_timestamp = @basename.sub(/^[0-9]+_/, '')
+          add_offense(node.loc.name) if snake_class_name != basename_without_timestamp
+        end
+
+        private
+
+        def to_snakecase(word)
+          word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2')
+          word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
+          word.tr!('-', '_')
+          word.downcase!
+          word
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -64,6 +64,7 @@
 require_relative 'rails/link_to_blank'
 require_relative 'rails/mailer_name'
 require_relative 'rails/match_route'
+require_relative 'rails/migration_file_name'
 require_relative 'rails/negate_include'
 require_relative 'rails/not_null_column'
 require_relative 'rails/order_by_id'

spec/rubocop/cop/rails/migration_file_name_spec.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::MigrationFileName, :config do
+  let(:filename) { 'db/migrate/20220101050505_create_users.rb' }
+
+  context 'when the file name matches its class' do
+    context 'with a super class' do
+      it do
+        expect_no_offenses(<<~RUBY, filename)
+          class CreateUsers < ActiveRecord::Migration[7.0]
+          end
+        RUBY
+      end
+    end
+
+    context 'without any super class' do
+      it do
+        expect_no_offenses(<<~RUBY, filename)
+          class CreateUsers
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when the file name does not match its class' do
+    it do
+      expect_offense(<<~RUBY, filename)
+        class SellBooks < ActiveRecord::Migration[7.0]
+              ^^^^^^^^^ The class name does not match with the file name.
+        end
+      RUBY
+    end
+  end
+end