Introduce a new FactoriesInMigrationSpecs cop

Signed-off-by: Rémy Coutable <remy@rymai.me>

rubocop/cop/rspec/factories_in_migration_specs.rb

@@ -0,0 +1,40 @@
+require_relative '../../spec_helpers'
+
+module RuboCop
+  module Cop
+    module RSpec
+      # This cop checks for the usage of factories in migration specs
+      #
+      # @example
+      #
+      #   # bad
+      #   let(:user) { create(:user) }
+      #
+      #   # good
+      #   let(:users) { table(:users) }
+      #   let(:user) { users.create!(name: 'User 1', username: 'user1') }
+      class FactoriesInMigrationSpecs < RuboCop::Cop::Cop
+        include SpecHelpers
+
+        MESSAGE = "Don't use FactoryBot.%s in migration specs, use `table` instead.".freeze
+        FORBIDDEN_METHODS = %i[build build_list create create_list].freeze
+
+        def_node_search :forbidden_factory_usage?, <<~PATTERN
+          (send {(const nil? :FactoryBot) nil?} {#{FORBIDDEN_METHODS.map(&:inspect).join(' ')}} ...)
+        PATTERN
+
+        # Following is what node.children looks like on a match:
+        # - Without FactoryBot namespace: [nil, :build, s(:sym, :user)]
+        # - With FactoryBot namespace: [s(:const, nil, :FactoryBot), :build, s(:sym, :user)]
+        def on_send(node)
+          return unless in_migration_spec?(node)
+          return unless forbidden_factory_usage?(node)
+
+          method = node.children[1]
+
+          add_offense(node, location: :expression, message: MESSAGE % method)
+        end
+      end
+    end
+  end
+end

rubocop/rubocop.rb

@@ -21,4 +21,5 @@ require_relative 'cop/migration/update_column_in_batches'
 require_relative 'cop/migration/update_large_table'
 require_relative 'cop/project_path_helper'
 require_relative 'cop/rspec/env_assignment'
+require_relative 'cop/rspec/factories_in_migration_specs'
 require_relative 'cop/sidekiq_options_queue'

rubocop/spec_helpers.rb

@@ -6,7 +6,18 @@ module RuboCop
     def in_spec?(node)
       path = node.location.expression.source_buffer.name
 
-      !SPEC_HELPERS.include?(File.basename(path)) && path.start_with?(File.join(Dir.pwd, 'spec'))
+      !SPEC_HELPERS.include?(File.basename(path)) &&
+        path.start_with?(File.join(Dir.pwd, 'spec'), File.join(Dir.pwd, 'ee', 'spec'))
+    end
+
+    # Returns true if the given node originated from a migration spec.
+    def in_migration_spec?(node)
+      path = node.location.expression.source_buffer.name
+
+      in_spec?(node) &&
+        path.start_with?(
+          File.join(Dir.pwd, 'spec', 'migrations'),
+          File.join(Dir.pwd, 'ee', 'spec', 'migrations'))
     end
   end
 end

spec/rubocop/cop/rspec/factories_in_migration_specs_spec.rb

@@ -0,0 +1,48 @@
+require 'spec_helper'
+
+require 'rubocop'
+require 'rubocop/rspec/support'
+
+require_relative '../../../../rubocop/cop/rspec/factories_in_migration_specs'
+
+describe RuboCop::Cop::RSpec::FactoriesInMigrationSpecs do
+  include CopHelper
+
+  let(:source_file) { 'spec/migrations/foo_spec.rb' }
+
+  subject(:cop) { described_class.new }
+
+  shared_examples 'an offensive factory call' do |namespace|
+    %i[build build_list create create_list].each do |forbidden_method|
+      namespaced_forbidden_method = "#{namespace}#{forbidden_method}(:user)"
+
+      it "registers an offense for #{namespaced_forbidden_method}" do
+        expect_offense(<<-RUBY)
+        describe 'foo' do
+          let(:user) { #{namespaced_forbidden_method} }
+                       #{'^' * namespaced_forbidden_method.size} Don't use FactoryBot.#{forbidden_method} in migration specs, use `table` instead.
+        end
+        RUBY
+      end
+    end
+  end
+
+  context 'in a migration spec file' do
+    before do
+      allow(cop).to receive(:in_migration_spec?).and_return(true)
+    end
+
+    it_behaves_like 'an offensive factory call', ''
+    it_behaves_like 'an offensive factory call', 'FactoryBot.'
+  end
+
+  context 'outside of a migration spec file' do
+    it "does not register an offense" do
+      expect_no_offenses(<<-RUBY)
+        describe 'foo' do
+          let(:user) { create(:user) }
+        end
+      RUBY
+    end
+  end
+end

spec/spec_helper.rb

@@ -66,6 +66,7 @@ RSpec.configure do |config|
   config.include MigrationsHelpers, :migration
   config.include StubFeatureFlags
   config.include StubENV
+  config.include ExpectOffense
 
   config.infer_spec_type_from_file_location!
 

spec/support/helpers/expect_offense.rb

@@ -0,0 +1,20 @@
+require 'rubocop/rspec/support'
+
+# https://github.com/backus/rubocop-rspec/blob/master/spec/support/expect_offense.rb
+# rubocop-rspec gem extension of RuboCop's ExpectOffense module.
+#
+# This mixin is the same as rubocop's ExpectOffense except the default
+# filename ends with `_spec.rb`
+module ExpectOffense
+  include RuboCop::RSpec::ExpectOffense
+
+  DEFAULT_FILENAME = 'example_spec.rb'.freeze
+
+  def expect_offense(source, filename = DEFAULT_FILENAME)
+    super
+  end
+
+  def expect_no_offenses(source, filename = DEFAULT_FILENAME)
+    super
+  end
+end