Add new InternalAffairs/RedundantDescribedClassAsSubject cop

This PR adds new `InternalAffairs/RedundantDescribedClassAsSubject` cop.
It checks for redundant `subject(:cop) { described_class.new }`.

```ruby
# bad
RSpec.describe RuboCop::Cop::Department::Foo do
  subject(:cop) { described_class.new(config) }
end

# good
RSpec.describe RuboCop::Cop::Department::Foo, :config do
end
```

No changelog entry has been added to the changelog due to this cop is
for use inside development.

And redundant `let(:config) { RuboCop::Config.new }` can also be removed.
I will prepare the implementation as a different cop.

lib/rubocop/cop/internal_affairs.rb

@@ -5,6 +5,7 @@
 require_relative 'internal_affairs/node_destructuring'
 require_relative 'internal_affairs/node_type_predicate'
 require_relative 'internal_affairs/offense_location_keyword'
+require_relative 'internal_affairs/redundant_described_class_as_subject'
 require_relative 'internal_affairs/redundant_message_argument'
 require_relative 'internal_affairs/redundant_location_argument'
 require_relative 'internal_affairs/style_detected_api_use'

lib/rubocop/cop/internal_affairs/redundant_described_class_as_subject.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module InternalAffairs
+      # This cop checks for redundant `subject(:cop) { described_class.new }`.
+      #
+      # @example
+      #   # bad
+      #   RSpec.describe RuboCop::Cop::Department::Foo do
+      #     subject(:cop) { described_class.new(config) }
+      #   end
+      #
+      #   # good
+      #   RSpec.describe RuboCop::Cop::Department::Foo, :config do
+      #   end
+      #
+      class RedundantDescribedClassAsSubject < Base
+        include RangeHelp
+        extend AutoCorrector
+
+        MSG = 'Remove the redundant `subject`%<additional_message>s.'
+
+        def_node_matcher :described_class_subject?, <<~PATTERN
+          (block
+            (send nil? :subject
+              (sym :cop))
+            (args)
+            (send
+              (send nil? :described_class) :new
+              $...))
+        PATTERN
+
+        def on_block(node)
+          return unless (described_class_arguments = described_class_subject?(node))
+          return if described_class_arguments.count >= 2
+
+          describe = find_describe_method_node(node)
+
+          unless (exist_config = describe.last_argument.source == ':config')
+            additional_message = ' and specify `:config` in `describe`'
+          end
+
+          message = format(MSG, additional_message: additional_message)
+
+          add_offense(node, message: message) do |corrector|
+            corrector.remove(range_by_whole_lines(node.source_range, include_final_newline: true))
+
+            corrector.insert_after(describe.last_argument, ', :config') unless exist_config
+          end
+        end
+
+        private
+
+        def find_describe_method_node(block_node)
+          block_node.ancestors.find { |node| node.block_type? && node.method?(:describe) }.send_node
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/internal_affairs/method_name_equal_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::MethodNameEqual do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::MethodNameEqual, :config do
   let(:config) { RuboCop::Config.new }
 
   it 'registers an offense when using `#method == :do_something`' do

spec/rubocop/cop/internal_affairs/node_destructuring_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::NodeDestructuring do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::NodeDestructuring, :config do
   context 'when destructuring using `node.children`' do
     it 'registers an offense when receiver is named `node`' do
       expect_offense(<<~RUBY, 'example_cop.rb')

spec/rubocop/cop/internal_affairs/node_type_predicate_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::NodeTypePredicate do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::NodeTypePredicate, :config do
   context 'comparison node type check' do
     it 'registers an offense and auto-corrects' do
       expect_offense(<<~RUBY)

spec/rubocop/cop/internal_affairs/offense_location_keyword_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::OffenseLocationKeyword do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::OffenseLocationKeyword, :config do
   context 'when `node.loc.selector` is passed' do
     it 'registers an offense' do
       expect_offense(<<~RUBY)

spec/rubocop/cop/internal_affairs/redundant_described_class_as_subject_spec.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::InternalAffairs::RedundantDescribedClassAsSubject, :config do
+  it 'registers an offense when using `subject(:cop)` and `:config` is not specified in `describe`' do
+    expect_offense(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition do
+        subject(:cop) { described_class.new(config) }
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Remove the redundant `subject` and specify `:config` in `describe`.
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition, :config do
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using `subject(:cop)` and `:config` is already specified in `describe`' do
+    expect_offense(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition, :config do
+        subject(:cop) { described_class.new(config) }
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Remove the redundant `subject`.
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition, :config do
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using `subject(:cop)` with no argument `described_class.new` and `:config` is specified' do
+    expect_offense(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition, :config do
+        subject(:cop) { described_class.new }
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Remove the redundant `subject`.
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition, :config do
+
+        let(:config) { RuboCop::Config.new }
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `subject(:cop)` with multiple arguments to `described_class.new`' do
+    expect_no_offenses(<<~RUBY)
+      RSpec.describe RuboCop::Cop::Lint::RegexpAsCondition do
+        subject(:cop) { described_class.new(config, options) }
+      end
+    RUBY
+  end
+end

spec/rubocop/cop/internal_affairs/redundant_location_argument_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::RedundantLocationArgument do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::RedundantLocationArgument, :config do
   context 'when location argument is passed' do
     context 'when location argument is :expression' do
       it 'registers an offense' do

spec/rubocop/cop/internal_affairs/redundant_message_argument_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::RedundantMessageArgument do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::RedundantMessageArgument, :config do
   context 'when `MSG` is passed' do
     it 'registers an offense' do
       expect_offense(<<~RUBY, 'example_cop.rb')

spec/rubocop/cop/internal_affairs/style_detected_api_use_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::StyleDetectedApiUse do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::StyleDetectedApiUse, :config do
   let(:config) { RuboCop::Config.new }
 
   it 'registers an offense when correct_style_detected is used without a negative *_style_detected follow up' do

spec/rubocop/cop/internal_affairs/useless_message_assertion_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::InternalAffairs::UselessMessageAssertion do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::InternalAffairs::UselessMessageAssertion, :config do
   it 'registers an offense for specs that assert using the MSG' do
     expect_offense(<<~RUBY, 'example_spec.rb')
       it 'uses described_class::MSG to specify the expected message' do

spec/rubocop/cop/layout/access_modifier_indentation_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::AccessModifierIndentation do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::AccessModifierIndentation, :config do
   let(:config) do
     c = cop_config.merge('SupportedStyles' => %w[indent outdent])
     RuboCop::Config

spec/rubocop/cop/layout/argument_alignment_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ArgumentAlignment do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::ArgumentAlignment, :config do
   let(:config) do
     RuboCop::Config.new('Layout/ArgumentAlignment' => cop_config,
                         'Layout/IndentationWidth' => {

spec/rubocop/cop/layout/array_alignment_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ArrayAlignment do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::ArrayAlignment, :config do
   let(:config) do
     RuboCop::Config.new('Layout/ArrayAlignment' => cop_config,
                         'Layout/IndentationWidth' => {

spec/rubocop/cop/layout/block_end_newline_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::BlockEndNewline do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::BlockEndNewline, :config do
   it 'accepts a one-liner' do
     expect_no_offenses('test do foo end')
   end

spec/rubocop/cop/layout/case_indentation_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::CaseIndentation do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::CaseIndentation, :config do
   let(:config) do
     merged = RuboCop::ConfigLoader
              .default_configuration['Layout/CaseIndentation'].merge(cop_config)

spec/rubocop/cop/layout/closing_heredoc_indentation_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ClosingHeredocIndentation do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::ClosingHeredocIndentation, :config do
   let(:config) do
     RuboCop::Config.new('Layout/ClosingHeredocIndentation' => cop_config)
   end

spec/rubocop/cop/layout/closing_parenthesis_indentation_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ClosingParenthesisIndentation do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::ClosingParenthesisIndentation, :config do
   context 'for method calls' do
     context 'with line break before 1st parameter' do
       it 'registers an offense for misaligned )' do

spec/rubocop/cop/layout/comment_indentation_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::CommentIndentation do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::CommentIndentation, :config do
   let(:config) do
     RuboCop::Config
       .new('Layout/IndentationWidth' => { 'Width' => indentation_width })

spec/rubocop/cop/layout/condition_position_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ConditionPosition do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::ConditionPosition, :config do
   %w[if unless while until].each do |keyword|
     it 'registers an offense and corrects for condition on the next line' do
       expect_offense(<<~RUBY)

spec/rubocop/cop/layout/else_alignment_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::ElseAlignment do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::ElseAlignment, :config do
   let(:config) do
     RuboCop::Config.new('Layout/EndAlignment' => end_alignment_config)
   end

spec/rubocop/cop/layout/empty_line_after_guard_clause_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterGuardClause do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterGuardClause, :config do
   it 'registers an offense and corrects a guard clause ' \
     'not followed by empty line' do
     expect_offense(<<~RUBY)

spec/rubocop/cop/layout/empty_line_after_magic_comment_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterMagicComment do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterMagicComment, :config do
   let(:config) { RuboCop::Config.new }
 
   it 'registers an offense for code that immediately follows comment' do

spec/rubocop/cop/layout/empty_line_after_multiline_condition_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterMultilineCondition do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLineAfterMultilineCondition, :config do
   it 'registers an offense when no new line after `if` with multiline condition' do
     expect_offense(<<~RUBY)
       if multiline &&

spec/rubocop/cop/layout/empty_lines_around_attribute_accessor_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundAttributeAccessor, :config do
-  subject(:cop) { described_class.new(config) }
-
   it 'registers an offense and corrects for code ' \
      'that immediately follows accessor' do
     expect_offense(<<~RUBY)

spec/rubocop/cop/layout/empty_lines_around_begin_body_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundBeginBody do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundBeginBody, :config do
   let(:config) { RuboCop::Config.new }
 
   shared_examples 'accepts' do |name, code|

spec/rubocop/cop/layout/empty_lines_around_exception_handling_keywords_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundExceptionHandlingKeywords do
-  subject(:cop) { described_class.new(config) }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundExceptionHandlingKeywords, :config do
   let(:config) { RuboCop::Config.new }
   let(:message) { '^{} Extra empty line detected' }
 

spec/rubocop/cop/layout/empty_lines_around_method_body_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundMethodBody do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLinesAroundMethodBody, :config do
   let(:beginning_offense_annotation) { '^{} Extra empty line detected at method body beginning.' }
   let(:end_offense_annotation) { '^{} Extra empty line detected at method body end.' }
 

spec/rubocop/cop/layout/empty_lines_spec.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
-RSpec.describe RuboCop::Cop::Layout::EmptyLines do
-  subject(:cop) { described_class.new }
-
+RSpec.describe RuboCop::Cop::Layout::EmptyLines, :config do
   it 'registers an offense for consecutive empty lines' do
     expect_offense(<<~RUBY)
       test = 5