Add new Rails/RedundantTravelBack cop

This PR adds new `Rails/RedundantTravelBack` cop. It checks for redundant `travel_back`.
Since Rails 5.2, `travel_back` automatically called at the end of the test.

```ruby
# bad
def teardown
  do_something
  travel_back
end

# good
def teardown
  do_something
end

# bad
after do
  do_something
  travel_back
end

# good
after do
  travel_back
end
```

It depends on `minimum_target_rails_version`, so it's packaged in this RuboCop Rails
instead of RuboCop RSpec.

Author: koic

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#521](https://github.com/rubocop/rubocop-rails/pull/521): Support auto-correction for `Rails/Output`. ([@koic][])
 * [#520](https://github.com/rubocop/rubocop-rails/pull/520): Support auto-correction for `Rails/ScopeArgs`. ([@koic][])
+* [#524](https://github.com/rubocop/rubocop-rails/pull/524): Add new `Rails/RedundantTravelBack` cop. ([@koic][])
 
 ## 2.11.3 (2021-07-11)
 

config/default.yml

@@ -608,6 +608,14 @@ Rails/RedundantReceiverInWithOptions:
   Enabled: true
   VersionAdded: '0.52'
 
+Rails/RedundantTravelBack:
+  Description: This cop checks for redundant `travel_back` calls.
+  Enabled: pending
+  VersionAdded: '2.12'
+  Include:
+    - spec/**/*.rb
+    - test/**/*.rb
+
 Rails/ReflectionClassName:
   Description: 'Use a string for `class_name` option value in the definition of a reflection.'
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -83,6 +83,7 @@ based on the https://rails.rubystyle.guide/[Rails Style Guide].
 * xref:cops_rails.adoc#railsredundantallownil[Rails/RedundantAllowNil]
 * xref:cops_rails.adoc#railsredundantforeignkey[Rails/RedundantForeignKey]
 * xref:cops_rails.adoc#railsredundantreceiverinwithoptions[Rails/RedundantReceiverInWithOptions]
+* xref:cops_rails.adoc#railsredundanttravelback[Rails/RedundantTravelBack]
 * xref:cops_rails.adoc#railsreflectionclassname[Rails/ReflectionClassName]
 * xref:cops_rails.adoc#railsrefutemethods[Rails/RefuteMethods]
 * xref:cops_rails.adoc#railsrelativedateconstant[Rails/RelativeDateConstant]

docs/modules/ROOT/pages/cops_rails.adoc

@@ -3452,6 +3452,58 @@ with_options options: false do |merger|
 end
 ----
 
+== Rails/RedundantTravelBack
+
+|===
+| Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
+
+| Pending
+| Yes
+| Yes
+| 2.12
+| -
+|===
+
+This cop checks for redundant `travel_back` calls.
+Since Rails 5.2, `travel_back` is automatically called at the end of the test.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+def teardown
+  do_something
+  travel_back
+end
+
+# good
+def teardown
+  do_something
+end
+
+# bad
+after do
+  do_something
+  travel_back
+end
+
+# good
+after do
+  do_something
+end
+----
+
+=== Configurable attributes
+
+|===
+| Name | Default value | Configurable values
+
+| Include
+| `spec/**/*.rb`, `test/**/*.rb`
+| Array
+|===
+
 == Rails/ReflectionClassName
 
 |===

lib/rubocop/cop/rails/redundant_travel_back.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Rails
+      # This cop checks for redundant `travel_back` calls.
+      # Since Rails 5.2, `travel_back` is automatically called at the end of the test.
+      #
+      # @example
+      #
+      #   # bad
+      #   def teardown
+      #     do_something
+      #     travel_back
+      #   end
+      #
+      #   # good
+      #   def teardown
+      #     do_something
+      #   end
+      #
+      #   # bad
+      #   after do
+      #     do_something
+      #     travel_back
+      #   end
+      #
+      #   # good
+      #   after do
+      #     do_something
+      #   end
+      #
+      class RedundantTravelBack < Base
+        include RangeHelp
+        extend AutoCorrector
+        extend TargetRailsVersion
+
+        minimum_target_rails_version 5.2
+
+        MSG = 'Redundant `travel_back` detected.'
+        RESTRICT_ON_SEND = %i[travel_back].freeze
+
+        def on_send(node)
+          return unless node.each_ancestor(:def, :block).any? do |ancestor|
+            method_name = ancestor.def_type? ? :teardown : :after
+
+            ancestor.method?(method_name)
+          end
+
+          add_offense(node) do |corrector|
+            corrector.remove(range_by_whole_lines(node.source_range, include_final_newline: true))
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rails_cops.rb

@@ -72,6 +72,7 @@
 require_relative 'rails/redundant_allow_nil'
 require_relative 'rails/redundant_foreign_key'
 require_relative 'rails/redundant_receiver_in_with_options'
+require_relative 'rails/redundant_travel_back'
 require_relative 'rails/reflection_class_name'
 require_relative 'rails/refute_methods'
 require_relative 'rails/relative_date_constant'

spec/rubocop/cop/rails/redundant_travel_back_spec.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::RedundantTravelBack, :config do
+  context '>= Rails 5.2', :rails52 do
+    it 'registers and corrects an offense when using `travel_back` in `teardown` method' do
+      expect_offense(<<~RUBY)
+        def teardown
+          do_something
+          travel_back
+          ^^^^^^^^^^^ Redundant `travel_back` detected.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        def teardown
+          do_something
+        end
+      RUBY
+    end
+
+    it 'registers and corrects an offense when using `travel_back` in `after` block' do
+      expect_offense(<<~RUBY)
+        after do
+          do_something
+          travel_back
+          ^^^^^^^^^^^ Redundant `travel_back` detected.
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        after do
+          do_something
+        end
+      RUBY
+    end
+
+    it 'does not register an offense when using `travel_back` outside of `teardown` method' do
+      expect_no_offenses(<<~RUBY)
+        def do_something
+          travel_back
+        end
+      RUBY
+    end
+
+    it 'does not register an offense when using `travel_back` outside of `after` block' do
+      expect_no_offenses(<<~RUBY)
+        do_something do
+          travel_back
+        end
+      RUBY
+    end
+  end
+
+  context '<= Rails 5.1', :rails51 do
+    it 'does not register an offense when using `travel_back` in `teardown` method' do
+      expect_no_offenses(<<~RUBY)
+        def teardown
+          do_something
+          travel_back
+        end
+      RUBY
+    end
+
+    it 'does not register an offense when using `travel_back` in `after` block' do
+      expect_no_offenses(<<~RUBY)
+        after do
+          do_something
+          travel_back
+        end
+      RUBY
+    end
+  end
+end