Added RuboCop cops to enforce code reuse rules

These Cops enforces the code reuse rules as defined in merge request
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21254.

6 files changed, 642 insertions, 0 deletions

diff --git a/spec/rubocop/cop/code_reuse/active_record_spec.rb b/spec/rubocop/cop/code_reuse/active_record_spec.rb
new file mode 100644
index 00000000000..a30fc52d26f
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/active_record_spec.rb
@@ -0,0 +1,138 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/active_record'
+
+describe RuboCop::Cop::CodeReuse::ActiveRecord do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of "where" without any arguments' do
+    expect_offense(<<~SOURCE)
+    def foo
+      User.where
+           ^^^^^ This method can only be used inside an ActiveRecord model
+    end
+    SOURCE
+  end
+
+  it 'flags the use of "where" with arguments' do
+    expect_offense(<<~SOURCE)
+    def foo
+      User.where(id: 10)
+           ^^^^^ This method can only be used inside an ActiveRecord model
+    end
+    SOURCE
+  end
+
+  it 'does not flag the use of "group" without any arguments' do
+    expect_no_offenses(<<~SOURCE)
+    def foo
+      project.group
+    end
+    SOURCE
+  end
+
+  it 'flags the use of "group" with arguments' do
+    expect_offense(<<~SOURCE)
+    def foo
+      project.group(:name)
+              ^^^^^ This method can only be used inside an ActiveRecord model
+    end
+    SOURCE
+  end
+
+  it 'does not flag the use of ActiveRecord models in a model' do
+    path = Rails.root.join('app', 'models', 'foo.rb').to_s
+
+    expect_no_offenses(<<~SOURCE, path)
+    def foo
+      project.group(:name)
+    end
+    SOURCE
+  end
+
+  it 'does not flag the use of ActiveRecord models in a spec' do
+    path = Rails.root.join('spec', 'foo_spec.rb').to_s
+
+    expect_no_offenses(<<~SOURCE, path)
+    def foo
+      project.group(:name)
+    end
+    SOURCE
+  end
+
+  it 'does not flag the use of ActiveRecord models in a background migration' do
+    path = Rails
+      .root
+      .join('lib', 'gitlab', 'background_migration', 'foo.rb')
+      .to_s
+
+    expect_no_offenses(<<~SOURCE, path)
+    def foo
+      project.group(:name)
+    end
+    SOURCE
+  end
+
+  it 'does not flag the use of ActiveRecord models in lib/gitlab/database' do
+    path = Rails.root.join('lib', 'gitlab', 'database', 'foo.rb').to_s
+
+    expect_no_offenses(<<~SOURCE, path)
+    def foo
+      project.group(:name)
+    end
+    SOURCE
+  end
+
+  it 'autocorrects offenses in instance methods by whitelisting them' do
+    corrected = autocorrect_source(<<~SOURCE)
+    def foo
+      User.where
+    end
+    SOURCE
+
+    expect(corrected).to eq(<<~SOURCE)
+    # rubocop: disable CodeReuse/ActiveRecord
+    def foo
+      User.where
+    end
+    # rubocop: enable CodeReuse/ActiveRecord
+    SOURCE
+  end
+
+  it 'autocorrects offenses in class methods by whitelisting them' do
+    corrected = autocorrect_source(<<~SOURCE)
+    def self.foo
+      User.where
+    end
+    SOURCE
+
+    expect(corrected).to eq(<<~SOURCE)
+    # rubocop: disable CodeReuse/ActiveRecord
+    def self.foo
+      User.where
+    end
+    # rubocop: enable CodeReuse/ActiveRecord
+    SOURCE
+  end
+
+  it 'autocorrects offenses in blocks by whitelisting them' do
+    corrected = autocorrect_source(<<~SOURCE)
+    get '/' do
+      User.where
+    end
+    SOURCE
+
+    expect(corrected).to eq(<<~SOURCE)
+    # rubocop: disable CodeReuse/ActiveRecord
+    get '/' do
+      User.where
+    end
+    # rubocop: enable CodeReuse/ActiveRecord
+    SOURCE
+  end
+end
diff --git a/spec/rubocop/cop/code_reuse/finder_spec.rb b/spec/rubocop/cop/code_reuse/finder_spec.rb
new file mode 100644
index 00000000000..b04e053a4c3
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/finder_spec.rb
@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/finder'
+
+describe RuboCop::Cop::CodeReuse::Finder do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of a Finder inside another Finder' do
+    allow(cop)
+      .to receive(:in_finder?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooFinder
+        def execute
+          BarFinder.new.execute
+          ^^^^^^^^^^^^^ Finders can not be used inside a Finder.
+        end
+      end
+    SOURCE
+
+    expect(cop.offenses.size).to eq(1)
+  end
+
+  it 'flags the use of a Finder inside a model class method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User
+        class << self
+          def second_method
+            BarFinder.new
+            ^^^^^^^^^^^^^ Finders can not be used inside model class methods.
+          end
+        end
+
+        def self.second_method
+          FooFinder.new
+          ^^^^^^^^^^^^^ Finders can not be used inside model class methods.
+        end
+      end
+    SOURCE
+  end
+
+  it 'does not flag the use of a Finder in a non Finder file' do
+    expect_no_offenses(<<~SOURCE)
+      class FooFinder
+        def execute
+          BarFinder.new.execute
+        end
+      end
+    SOURCE
+  end
+
+  it 'does not flag the use of a Finder in a regular class method' do
+    expect_no_offenses(<<~SOURCE)
+      class User
+        class << self
+          def second_method
+            BarFinder.new
+          end
+        end
+
+        def self.second_method
+          FooFinder.new
+        end
+      end
+    SOURCE
+  end
+end
diff --git a/spec/rubocop/cop/code_reuse/presenter_spec.rb b/spec/rubocop/cop/code_reuse/presenter_spec.rb
new file mode 100644
index 00000000000..4fe72619273
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/presenter_spec.rb
@@ -0,0 +1,117 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/presenter'
+
+describe RuboCop::Cop::CodeReuse::Presenter do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of a Presenter in a Service class' do
+    allow(cop)
+      .to receive(:in_service_class?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooService
+        def execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a Service class.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Presenter in a Finder' do
+    allow(cop)
+      .to receive(:in_finder?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooFinder
+        def execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a Finder.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Service class in a Presenter' do
+    allow(cop)
+      .to receive(:in_presenter?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooPresenter
+        def execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a Presenter.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Presenter in a Serializer' do
+    allow(cop)
+      .to receive(:in_serializer?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooSerializer
+        def execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a Serializer.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Presenter in a model instance method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Base
+        def execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a model.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Presenter in a model class method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Base
+        def self.execute
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a model.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Presenter in a worker' do
+    allow(cop)
+      .to receive(:in_worker?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooWorker
+        def perform
+          FooPresenter.new.execute
+          ^^^^^^^^^^^^^^^^ Presenters can not be used in a worker.
+        end
+      end
+    SOURCE
+  end
+end
diff --git a/spec/rubocop/cop/code_reuse/serializer_spec.rb b/spec/rubocop/cop/code_reuse/serializer_spec.rb
new file mode 100644
index 00000000000..4530b15eed7
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/serializer_spec.rb
@@ -0,0 +1,117 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/serializer'
+
+describe RuboCop::Cop::CodeReuse::Serializer do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of a Serializer in a Service class' do
+    allow(cop)
+      .to receive(:in_service_class?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooService
+        def execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a Service class.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a Finder' do
+    allow(cop)
+      .to receive(:in_finder?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooFinder
+        def execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a Finder.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a Presenter' do
+    allow(cop)
+      .to receive(:in_presenter?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooPresenter
+        def execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a Presenter.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a Serializer' do
+    allow(cop)
+      .to receive(:in_serializer?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooSerializer
+        def execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a Serializer.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a model instance method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Base
+        def execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a model.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a model class method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Base
+        def self.execute
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a model.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Serializer in a worker' do
+    allow(cop)
+      .to receive(:in_worker?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooWorker
+        def perform
+          FooSerializer.new.execute
+          ^^^^^^^^^^^^^^^^^ Serializers can not be used in a worker.
+        end
+      end
+    SOURCE
+  end
+end
diff --git a/spec/rubocop/cop/code_reuse/service_class_spec.rb b/spec/rubocop/cop/code_reuse/service_class_spec.rb
new file mode 100644
index 00000000000..7b8d82f332e
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/service_class_spec.rb
@@ -0,0 +1,89 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/service_class'
+
+describe RuboCop::Cop::CodeReuse::ServiceClass do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of a Service class in a Finder' do
+    allow(cop)
+      .to receive(:in_finder?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooFinder
+        def execute
+          FooService.new.execute
+          ^^^^^^^^^^^^^^ Service classes can not be used in a Finder.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Service class in a Presenter' do
+    allow(cop)
+      .to receive(:in_presenter?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooPresenter
+        def execute
+          FooService.new.execute
+          ^^^^^^^^^^^^^^ Service classes can not be used in a Presenter.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Service class in a Serializer' do
+    allow(cop)
+      .to receive(:in_serializer?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooSerializer
+        def execute
+          FooService.new.execute
+          ^^^^^^^^^^^^^^ Service classes can not be used in a Serializer.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a Service class in a model' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Model
+        class << self
+          def first
+            FooService.new.execute
+            ^^^^^^^^^^^^^^ Service classes can not be used in a model.
+          end
+        end
+
+        def second
+          FooService.new.execute
+          ^^^^^^^^^^^^^^ Service classes can not be used in a model.
+        end
+      end
+    SOURCE
+  end
+
+  it 'does not flag the use of a Service class in a regular class' do
+    expect_no_offenses(<<~SOURCE)
+      class Foo
+        def execute
+          FooService.new.execute
+        end
+      end
+    SOURCE
+  end
+end
diff --git a/spec/rubocop/cop/code_reuse/worker_spec.rb b/spec/rubocop/cop/code_reuse/worker_spec.rb
new file mode 100644
index 00000000000..97acaeb7643
--- /dev/null
+++ b/spec/rubocop/cop/code_reuse/worker_spec.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/code_reuse/worker'
+
+describe RuboCop::Cop::CodeReuse::Worker do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of a worker in a controller' do
+    allow(cop)
+      .to receive(:in_controller?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooController
+        def index
+          FooWorker.perform_async
+          ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in a controller.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a worker in an API' do
+    allow(cop)
+      .to receive(:in_api?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class Foo < Grape::API
+        resource :projects do
+          get '/' do
+            FooWorker.perform_async
+            ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in a Grape API.
+          end
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a worker in a Finder' do
+    allow(cop)
+      .to receive(:in_finder?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooFinder
+        def execute
+          FooWorker.perform_async
+          ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in a Finder.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a worker in a Presenter' do
+    allow(cop)
+      .to receive(:in_presenter?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooPresenter
+        def execute
+          FooWorker.perform_async
+          ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in a Presenter.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a worker in a Serializer' do
+    allow(cop)
+      .to receive(:in_serializer?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class FooSerializer
+        def execute
+          FooWorker.perform_async
+          ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in a Serializer.
+        end
+      end
+    SOURCE
+  end
+
+  it 'flags the use of a worker in a model class method' do
+    allow(cop)
+      .to receive(:in_model?)
+      .and_return(true)
+
+    expect_offense(<<~SOURCE)
+      class User < ActiveRecord::Base
+        def self.execute
+          FooWorker.perform_async
+          ^^^^^^^^^^^^^^^^^^^^^^^ Workers can not be used in model class methods.
+        end
+      end
+    SOURCE
+  end
+end