New Migration/UpdateColumnInBatches cop

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

rubocop/cop/migration/update_column_in_batches.rb

@@ -0,0 +1,43 @@
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      # Cop that checks if a spec file exists for any migration using
+      # `update_column_in_batches`.
+      class UpdateColumnInBatches < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        MSG = 'Migration running `update_column_in_batches` must have a spec file at' \
+          ' `%s`.'.freeze
+
+        def on_send(node)
+          return unless in_migration?(node)
+          return unless node.children[1] == :update_column_in_batches
+
+          spec_path = spec_filename(node)
+
+          unless File.exist?(File.expand_path(spec_path, rails_root))
+            add_offense(node, :expression, format(MSG, spec_path))
+          end
+        end
+
+        private
+
+        def spec_filename(node)
+          source_name = node.location.expression.source_buffer.name
+          path = Pathname.new(source_name).relative_path_from(rails_root)
+          dirname = File.dirname(path)
+            .sub(%r{\Adb/(migrate|post_migrate)}, 'spec/migrations')
+          filename = File.basename(source_name, '.rb').sub(%r{\A\d+_}, '')
+
+          File.join(dirname, "#{filename}_spec.rb")
+        end
+
+        def rails_root
+          Pathname.new(File.expand_path('../../..', __dir__))
+        end
+      end
+    end
+  end
+end

rubocop/migration_helpers.rb

@@ -3,8 +3,9 @@ module RuboCop
   module MigrationHelpers
     # Returns true if the given node originated from the db/migrate directory.
     def in_migration?(node)
-      File.dirname(node.location.expression.source_buffer.name).
-        end_with?('db/migrate')
+      dirname = File.dirname(node.location.expression.source_buffer.name)
+
+      dirname.end_with?('db/migrate', 'db/post_migrate')
     end
   end
 end

rubocop/rubocop.rb

@@ -8,3 +8,4 @@ require_relative 'cop/migration/add_index'
 require_relative 'cop/migration/remove_concurrent_index'
 require_relative 'cop/migration/remove_index'
 require_relative 'cop/migration/reversible_add_column_with_default'
+require_relative 'cop/migration/update_column_in_batches'

spec/rubocop/cop/migration/update_column_in_batches_spec.rb

@@ -0,0 +1,94 @@
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/migration/update_column_in_batches'
+
+describe RuboCop::Cop::Migration::UpdateColumnInBatches do
+  let(:cop) { described_class.new }
+  let(:tmp_rails_root) { Rails.root.join('tmp', 'rails_root') }
+  let(:migration_code) do
+    <<-END
+    def up
+      update_column_in_batches(:projects, :name, "foo") do |table, query|
+        query.where(table[:name].eq(nil))
+      end
+    end
+    END
+  end
+
+  before do
+    allow(cop).to receive(:rails_root).and_return(tmp_rails_root)
+  end
+  after do
+    FileUtils.rm_rf(tmp_rails_root)
+  end
+
+  context 'outside of a migration' do
+    it 'does not register any offenses' do
+      inspect_source(cop, migration_code)
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  let(:spec_filepath) { tmp_rails_root.join('spec', 'migrations', 'my_super_migration_spec.rb') }
+
+  shared_context 'with a migration file' do
+    before do
+      FileUtils.mkdir_p(File.dirname(migration_filepath))
+      @migration_file = File.new(migration_filepath, 'w+')
+    end
+    after do
+      @migration_file.close
+    end
+  end
+
+  shared_examples 'a migration file with no spec file' do
+    include_context 'with a migration file'
+
+    let(:relative_spec_filepath) { Pathname.new(spec_filepath).relative_path_from(tmp_rails_root) }
+
+    it 'registers an offense when using update_column_in_batches' do
+      inspect_source(cop, migration_code, @migration_file)
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(1)
+        expect(cop.offenses.map(&:line)).to eq([2])
+        expect(cop.offenses.first.message).
+          to include("`#{relative_spec_filepath}`")
+      end
+    end
+  end
+
+  shared_examples 'a migration file with a spec file' do
+    include_context 'with a migration file'
+
+    before do
+      FileUtils.mkdir_p(File.dirname(spec_filepath))
+      @spec_file = File.new(spec_filepath, 'w+')
+    end
+    after do
+      @spec_file.close
+    end
+
+    it 'does not register any offenses' do
+      inspect_source(cop, migration_code, @migration_file)
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  context 'in a migration' do
+    let(:migration_filepath) { tmp_rails_root.join('db', 'migrate', '20121220064453_my_super_migration.rb') }
+
+    it_behaves_like 'a migration file with no spec file'
+    it_behaves_like 'a migration file with a spec file'
+  end
+
+  context 'in a post migration' do
+    let(:migration_filepath) { tmp_rails_root.join('db', 'post_migrate', '20121220064453_my_super_migration.rb') }
+
+    it_behaves_like 'a migration file with no spec file'
+    it_behaves_like 'a migration file with a spec file'
+  end
+end