[Fix #3167] Added VariableNumber Cop

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#3360](https://github.com/bbatsov/rubocop/issues/3360): Add `RequireForNonPublicMethods` configuration option to `Style/DocumentationMethod` cop. ([@drenmi][])
 * Add new `Rails/SafeNavigation` cop to convert `try!` to `&.`. ([@rrosenblum][])
 * [#3415](https://github.com/bbatsov/rubocop/pull/3415): Add new `Rails/NotNullColumn` cop. ([@pocke][])
+* [#3167](https://github.com/bbatsov/rubocop/issues/3167): Add new `Style/VariableNumber` cop. ([@sooyang][])
 
 ### Bug fixes
 

config/default.yml

@@ -1048,6 +1048,13 @@ Style/VariableName:
     - snake_case
     - camelCase
 
+Style/VariableNumber:
+  EnforcedStyle: normalcase
+  SupportedStyles:
+    - snake_case
+    - normalcase
+    - non_integer
+
 Style/WhileUntilModifier:
   MaxLineLength: 80
 

config/enabled.yml

@@ -912,6 +912,10 @@ Style/VariableName:
   StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#snake-case-symbols-methods-vars'
   Enabled: true
 
+Style/VariableNumber:
+  Description: 'Use the configured style when numbering variables.'
+  Enabled: true
+
 Style/WhenThen:
   Description: 'Use when x then ... for one-line cases.'
   StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#one-line-cases'

lib/rubocop.rb

@@ -56,6 +56,7 @@
 require 'rubocop/cop/mixin/classish_length' # relies on code_length
 require 'rubocop/cop/mixin/configurable_enforced_style'
 require 'rubocop/cop/mixin/configurable_naming'
+require 'rubocop/cop/mixin/configurable_numbering'
 require 'rubocop/cop/mixin/def_node'
 require 'rubocop/cop/mixin/documentation_comment'
 require 'rubocop/cop/mixin/empty_lines_around_body'
@@ -371,6 +372,7 @@
 require 'rubocop/cop/style/unneeded_percent_q'
 require 'rubocop/cop/style/variable_interpolation'
 require 'rubocop/cop/style/variable_name'
+require 'rubocop/cop/style/variable_number'
 require 'rubocop/cop/style/when_then'
 require 'rubocop/cop/style/while_until_do'
 require 'rubocop/cop/style/while_until_modifier'

lib/rubocop/cop/mixin/configurable_numbering.rb

@@ -0,0 +1,52 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    # This module provides functionality for checking if numbering match the
+    # configured EnforcedStyle.
+    module ConfigurableNumbering
+      include ConfigurableEnforcedStyle
+
+      SNAKE_CASE = /^@{0,2}[-_a-z]+[_\D]*(_\d)*[!?=]?$/
+      NORMAL_CASE = /^@{0,2}-{0,1}_{0,1}[a-zA-Z\d]*[_\D]*[!?=]?$/
+      NON_INTEGER = /^@{0,2}[-_a-z]+[_\D]*[!?=]?$/
+
+      def check_name(node, name, name_range)
+        return if operator?(name)
+
+        if valid_name?(node, name)
+          correct_style_detected
+        else
+          add_offense(node, name_range, message(style))
+        end
+      end
+
+      def valid_name?(node, name)
+        pattern =
+          case style
+          when :snake_case
+            SNAKE_CASE
+          when :normalcase
+            NORMAL_CASE
+          when :non_integer
+            NON_INTEGER
+          end
+        name.match(pattern) || class_emitter_method?(node, name)
+      end
+
+      # A class emitter method is a singleton method in a class/module, where
+      # the method has the same name as a class defined in the class/module.
+      def class_emitter_method?(node, name)
+        return false unless node.parent && node.defs_type?
+        # a class emitter method may be defined inside `def self.included`,
+        # `def self.extended`, etc.
+        node = node.parent while node.parent.defs_type?
+
+        node.parent.each_child_node(:class).any? do |c|
+          c.loc.name.is?(name.to_s)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/style/braces_around_hash_parameters.rb

@@ -39,13 +39,13 @@ def check(arg, args)
         end
 
         def check_context_dependent(arg, args)
-          braces_around_2nd_from_end = args.length > 1 && args[-2].hash_type?
+          braces_around_second_from_end = args.length > 1 && args[-2].hash_type?
           if braces?(arg)
-            unless braces_around_2nd_from_end
+            unless braces_around_second_from_end
               add_offense(arg.parent, arg.source_range,
                           format(MSG, 'Redundant'))
             end
-          elsif braces_around_2nd_from_end
+          elsif braces_around_second_from_end
             add_offense(arg.parent, arg.source_range, format(MSG, 'Missing'))
           end
         end

lib/rubocop/cop/style/variable_number.rb

@@ -0,0 +1,79 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # This cop makes sure that all numbered variables use the
+      # configured style, snake_case, normalcase or non_integer,
+      # for their numbering.
+      #
+      # @example
+      #   "EnforcedStyle => 'snake_case'"
+      #
+      #   # bad
+      #
+      #   variable1 = 1
+      #
+      #   # good
+      #
+      #   variable_1 = 1
+      #
+      # @example
+      #   "EnforcedStyle => 'normalcase'"
+      #
+      #   # bad
+      #
+      #   variable_1 = 1
+      #
+      #   # good
+      #
+      #   variable1 = 1
+      #
+      # @example
+      #   "EnforcedStyle => 'non_integer'"
+      #
+      #   #bad
+      #
+      #   variable1 = 1
+      #
+      #   variable_1 = 1
+      #
+      #   #good
+      #
+      #   variableone = 1
+      #
+      #   variable_one = 1
+      #
+      class VariableNumber < Cop
+        include ConfigurableNumbering
+
+        def on_lvasgn(node)
+          name, = *node
+          check_name(node, name, node.loc.name)
+        end
+
+        def on_ivasgn(node)
+          name, = *node
+          check_name(node, name, node.loc.name)
+        end
+
+        def on_cvasgn(node)
+          name, = *node
+          check_name(node, name, node.loc.name)
+        end
+
+        def on_arg(node)
+          name, = *node
+          check_name(node, name, node.loc.name)
+        end
+
+        private
+
+        def message(style)
+          format('Use %s for variable numbers.', style)
+        end
+      end
+    end
+  end
+end