From 8b2f3c60abe0cc42af05e2efecb0d2dfca744080 Mon Sep 17 00:00:00 2001
From: Hugo Hache <hugo.hache@spaceable.org>
Date: Mon, 20 Sep 2021 15:51:56 +0200
Subject: [PATCH] Add new Style/NumberedParameters cop

---
 ...new_add_new_stylenumberedparameters_cop.md |  3 ++
 config/default.yml                            |  9 ++++
 lib/rubocop.rb                                |  1 +
 lib/rubocop/cop/style/numbered_parameters.rb  | 46 +++++++++++++++++++
 .../cop/style/numbered_parameters_spec.rb     | 35 ++++++++++++++
 5 files changed, 94 insertions(+)
 create mode 100644 changelog/new_add_new_stylenumberedparameters_cop.md
 create mode 100644 lib/rubocop/cop/style/numbered_parameters.rb
 create mode 100644 spec/rubocop/cop/style/numbered_parameters_spec.rb

diff --git a/changelog/new_add_new_stylenumberedparameters_cop.md b/changelog/new_add_new_stylenumberedparameters_cop.md
new file mode 100644
index 00000000000..5fac75f2765
--- /dev/null
+++ b/changelog/new_add_new_stylenumberedparameters_cop.md
@@ -0,0 +1,3 @@
+* [#10100](https://github.com/rubocop/rubocop/pull/10100): Add new Style/NumberedParameters cop. ([@Hugo-Hache][])
+
+[@Hugo-Hache]: https://github.com/Hugo-Hache
diff --git a/config/default.yml b/config/default.yml
index d491dfdb64a..6e99897a826 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -4135,6 +4135,15 @@ Style/Not:
   VersionAdded: '0.9'
   VersionChanged: '0.20'
 
+Style/NumberedParameters:
+  Description: 'Restrict the usage of numbered parameters.'
+  Enabled: pending
+  VersionAdded: '<<next>>'
+  EnforcedStyle: allow_single_line
+  SupportedStyles:
+    - allow_single_line
+    - disallow
+
 Style/NumberedParametersLimit:
   Description: 'Avoid excessive numbered params in a single block.'
   Enabled: pending
diff --git a/lib/rubocop.rb b/lib/rubocop.rb
index 1298bc2bd87..2815286fca1 100644
--- a/lib/rubocop.rb
+++ b/lib/rubocop.rb
@@ -513,6 +513,7 @@
 require_relative 'rubocop/cop/style/method_call_without_args_parentheses'
 require_relative 'rubocop/cop/style/method_call_with_args_parentheses'
 require_relative 'rubocop/cop/style/multiline_in_pattern_then'
+require_relative 'rubocop/cop/style/numbered_parameters'
 require_relative 'rubocop/cop/style/redundant_assignment'
 require_relative 'rubocop/cop/style/redundant_fetch_block'
 require_relative 'rubocop/cop/style/redundant_file_extension_in_require'
diff --git a/lib/rubocop/cop/style/numbered_parameters.rb b/lib/rubocop/cop/style/numbered_parameters.rb
new file mode 100644
index 00000000000..9f13ca31747
--- /dev/null
+++ b/lib/rubocop/cop/style/numbered_parameters.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # This cop checks for numbered parameters.
+      #
+      # It can either restrict the use of numbered parameters to
+      # single-lined blocks, or disallow completely numbered parameters.
+      #
+      # @example EnforcedStyle: allow_single_line (default)
+      #   # bad
+      #   collection.each do
+      #     puts _1
+      #   end
+      #
+      #   # good
+      #   collection.each { puts _1 }
+      #
+      # @example EnforcedStyle: disallow
+      #   # bad
+      #   collection.each { puts _1 }
+      #
+      #   # good
+      #   collection.each { |item| puts item }
+      #
+      class NumberedParameters < Base
+        include ConfigurableEnforcedStyle
+        extend TargetRubyVersion
+
+        MSG_DISALLOW = 'Avoid using numbered parameters.'
+        MSG_MULTI_LINE = 'Avoid using numbered parameters for multi-line blocks.'
+
+        minimum_target_ruby_version 2.7
+
+        def on_numblock(node)
+          if style == :disallow
+            add_offense(node, message: MSG_DISALLOW)
+          elsif node.multiline?
+            add_offense(node, message: MSG_MULTI_LINE)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/rubocop/cop/style/numbered_parameters_spec.rb b/spec/rubocop/cop/style/numbered_parameters_spec.rb
new file mode 100644
index 00000000000..0feeee0fbfb
--- /dev/null
+++ b/spec/rubocop/cop/style/numbered_parameters_spec.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Style::NumberedParameters, :config do
+  context '>= Ruby 2.7', :ruby27 do
+    context 'EnforcedStyle: allow_single_line' do
+      let(:cop_config) { { 'EnforcedStyle' => 'allow_single_line' } }
+
+      it 'registers an offense when using numbered parameters with multi-line blocks' do
+        expect_offense(<<~RUBY)
+          collection.each do
+          ^^^^^^^^^^^^^^^^^^ Avoid using numbered parameters for multi-line blocks.
+            puts _1
+          end
+        RUBY
+      end
+
+      it 'does not register an offense when using numbered parameters with single-line blocks' do
+        expect_no_offenses(<<~RUBY)
+          collection.each { puts _1 }
+        RUBY
+      end
+    end
+
+    context 'EnforcedStyle: disallow' do
+      let(:cop_config) { { 'EnforcedStyle' => 'disallow' } }
+
+      it 'does an offense when using numbered parameters even with single-line blocks' do
+        expect_offense(<<~RUBY)
+          collection.each { puts _1 }
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Avoid using numbered parameters.
+        RUBY
+      end
+    end
+  end
+end