[Fix rubocop#5356] Add new Lint/UnneededCopEnableDirective cop

config/enabled.yml

@@ -690,6 +690,11 @@ Lint/UnneededCopDisableDirective:
                  It must be explicitly disabled.
   Enabled: true
 
+Lint/UnneededCopEnableDirective:
+  Description: Checks for rubocop:enable comments that can be removed.
+
+  Enabled: true
+
 Lint/UnneededRequireStatement:
   Description: 'Checks for unnecessary `require` statement.'
   Enabled: true

lib/rubocop.rb

@@ -296,6 +296,7 @@
 require_relative 'rubocop/cop/lint/underscore_prefixed_variable_name'
 require_relative 'rubocop/cop/lint/unified_integer'
 require_relative 'rubocop/cop/lint/unneeded_cop_disable_directive'
+require_relative 'rubocop/cop/lint/unneeded_cop_enable_directive'
 require_relative 'rubocop/cop/lint/unneeded_require_statement'
 require_relative 'rubocop/cop/lint/unneeded_splat_expansion'
 require_relative 'rubocop/cop/lint/unreachable_code'

lib/rubocop/comment_config.rb

@@ -34,8 +34,29 @@ def cop_disabled_line_ranges
       @cop_disabled_line_ranges ||= analyze
     end
 
+    def extra_enabled_comments
+      extra_enabled_comments_with_names([], {})
+    end
+
     private
 
+    def extra_enabled_comments_with_names(extras, names)
+      each_directive do |comment, cop_names, disabled|
+        next unless comment_only_line?(comment.loc.expression.line)
+        cop_names.each do |name|
+          names[name] ||= 0
+          if disabled
+            names[name] += 1
+          elsif names[name] > 0
+            names[name] -= 1
+          else
+            extras << [comment, name]
+          end
+        end
+      end
+      extras
+    end
+
     def analyze
       analyses = Hash.new { |hash, key| hash[key] = CopAnalysis.new([], nil) }
 

lib/rubocop/cop/lint/unneeded_cop_enable_directive.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+# The Lint/UnneededCopEnableDirective cop needs to be disabled so as
+# to be able to provide a (bad) example of an unneeded enable.
+
+# rubocop:disable Lint/UnneededCopEnableDirective
+module RuboCop
+  module Cop
+    module Lint
+      # This cop detects instances of rubocop:enable comments that can be
+      # removed.
+      #
+      # @example
+      #   # bad
+      #   foo = 1
+      #   # rubocop:enable Metrics/LineLength
+      #
+      #   # good
+      #   foo = 1
+      class UnneededCopEnableDirective < Cop
+        include RangeHelp
+
+        MSG = 'Unnecessary enabling of %<cop>s.'.freeze
+
+        def investigate(processed_source)
+          return if processed_source.blank?
+          offenses = processed_source.comment_config.extra_enabled_comments
+          offenses.each do |comment, name|
+            add_offense(
+              [comment, name],
+              location: range_of_offense(comment, name),
+              message: format(MSG, cop: name)
+            )
+          end
+        end
+
+        def autocorrect(comment_and_name)
+          lambda do |corrector|
+            comment, name = *comment_and_name
+            range = range_of_offense(*comment_and_name)
+            index = cop_name_indention(comment, name)
+            make_corrections(corrector, comment, name, range, index)
+          end
+        end
+
+        private
+
+        def range_of_offense(comment, name)
+          comment_start = comment.loc.expression.begin_pos
+          offense_start = comment_start + cop_name_indention(comment, name)
+          range_between(offense_start, offense_start + name.size)
+        end
+
+        def cop_name_indention(comment, name)
+          comment.text.index(name)
+        end
+
+        # rubocop:disable Metrics/AbcSize
+        def make_corrections(corrector, comment, name, range, index)
+          if comment.text[index - 2] == ','
+            corrector.remove(
+              range_between(range.begin_pos - 2, range.end_pos)
+            )
+          elsif comment.text[index + name.size] == ','
+            corrector.remove(
+              range_between(range.begin_pos, range.end_pos + 2)
+            )
+          else
+            corrector.remove(comment.loc.expression)
+          end
+        end
+        # rubocop:enable Metrics/AbcSize
+      end
+    end
+  end
+end
+# rubocop:enable Lint/UnneededCopEnableDirective

spec/rubocop/cli_spec.rb

@@ -302,9 +302,10 @@ def and_with_args
         .to eq(['example.rb: Style/LineLength has the wrong ' \
                 'namespace - should be Metrics',
                 ''].join("\n"))
-      # 3 cops were disabled, then 2 were enabled again, so we
-      # should get 2 offenses reported.
+      # 2 real cops were disabled, and 1 that was incorrect
+      # 2 real cops was enabled, but only 1 had been disabled correctly
       expect($stdout.string).to eq(<<-RESULT.strip_indent)
+        #{abs('example.rb')}:6:21: W: Lint/UnneededCopEnableDirective: Unnecessary enabling of Metrics/LineLength.
         #{abs('example.rb')}:7:81: C: Metrics/LineLength: Line is too long. [95/80]
         #{abs('example.rb')}:9:5: C: Style/StringLiterals: Prefer single-quoted strings when you don't need string interpolation or special symbols.
       RESULT

spec/rubocop/cop/lint/unneeded_cop_enable_directive_spec.rb

@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Lint::UnneededCopEnableDirective do
+  subject(:cop) { described_class.new }
+
+  it 'registers offense for unnecessary enable' do
+    expect_offense(<<-RUBY.strip_indent)
+      foo
+      # rubocop:enable Metrics/LineLength
+                       ^^^^^^^^^^^^^^^^^^ Unnecessary enabling of Metrics/LineLength.
+    RUBY
+  end
+
+  it 'registers multiple offenses for same comment' do
+    expect_offense(<<-RUBY.strip_indent)
+      foo
+      # rubocop:enable Metrics/ModuleLength, Metrics/AbcSize
+                                             ^^^^^^^^^^^^^^^ Unnecessary enabling of Metrics/AbcSize.
+                       ^^^^^^^^^^^^^^^^^^^^ Unnecessary enabling of Metrics/ModuleLength.
+      bar
+    RUBY
+  end
+
+  it 'registers correct offense when combined with necessary enable' do
+    expect_offense(<<-RUBY.strip_indent)
+      # rubocop:disable Metrics/LineLength
+      fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo = barrrrrrrrrrrrrrrrrrrrrrrrrr
+      # rubocop:enable Metrics/AbcSize, Metrics/LineLength
+                       ^^^^^^^^^^^^^^^ Unnecessary enabling of Metrics/AbcSize.
+      bar
+    RUBY
+  end
+
+  context 'autocorrection' do
+    context 'when entire comment unnecessarily enables' do
+      let(:source) do
+        <<-RUBY.strip_indent
+          foo
+          # rubocop:enable Metrics/LineLength
+        RUBY
+      end
+
+      it 'removes unnecessary enables' do
+        corrected = autocorrect_source(source)
+        expect(corrected).to eq(<<-RUBY.strip_indent)
+          foo
+
+        RUBY
+      end
+    end
+
+    context 'when first cop unnecessarily enables' do
+      let(:source) do
+        <<-RUBY.strip_indent
+          # rubocop:disable Metrics/LineLength
+          foo
+          # rubocop:enable Metrics/AbcSize, Metrics/LineLength
+        RUBY
+      end
+
+      it 'removes unnecessary enables' do
+        corrected = autocorrect_source(source)
+        expect(corrected).to eq(<<-RUBY.strip_indent)
+          # rubocop:disable Metrics/LineLength
+          foo
+          # rubocop:enable Metrics/LineLength
+        RUBY
+      end
+    end
+
+    context 'when last cop unnecessarily enables' do
+      let(:source) do
+        <<-RUBY.strip_indent
+          # rubocop:disable Metrics/LineLength
+          foo
+          # rubocop:enable Metrics/LineLength, Metrics/AbcSize
+        RUBY
+      end
+
+      it 'removes unnecessary enables' do
+        corrected = autocorrect_source(source)
+        expect(corrected).to eq(<<-RUBY.strip_indent)
+          # rubocop:disable Metrics/LineLength
+          foo
+          # rubocop:enable Metrics/LineLength
+        RUBY
+      end
+    end
+
+    context 'when middle cop unnecessarily enables' do
+      let(:source) do
+        <<-RUBY.strip_indent
+          # rubocop:disable Metrics/LineLength, Lint/Debugger
+          foo
+          # rubocop:enable Metrics/LineLength, Metrics/AbcSize, Lint/Debugger
+        RUBY
+      end
+
+      it 'removes unnecessary enables' do
+        corrected = autocorrect_source(source)
+        expect(corrected).to eq(<<-RUBY.strip_indent)
+          # rubocop:disable Metrics/LineLength, Lint/Debugger
+          foo
+          # rubocop:enable Metrics/LineLength, Lint/Debugger
+        RUBY
+      end
+    end
+  end
+end