Drop Ruby 2.4 support

This PR drops Ruby 2.4 support. The next release will be the time to
drop Ruby 2.4 support.

- https://www.ruby-lang.org/en/news/2020/04/05/support-of-ruby-2-4-has-ended/
- https://docs.rubocop.org/rubocop/1.12/compatibility.html#support-matrix

.circleci/config.yml

@@ -46,29 +46,6 @@ rubocop_steps: &rubocop_steps
 
 jobs:
 
-  # Ruby 2.4
-  ruby-2.4-spec:
-    docker:
-      - image: circleci/ruby:2.4
-    environment:
-      <<: *common_env
-    steps:
-      *spec_steps
-  ruby-2.4-ascii_spec:
-    docker:
-      - image: circleci/ruby:2.4
-    environment:
-      <<: *common_env
-    steps:
-      *ascii_spec_steps
-  ruby-2.4-rubocop:
-    docker:
-      - image: circleci/ruby:2.4
-    environment:
-      <<: *common_env
-    steps:
-      *rubocop_steps
-
   # Ruby 2.5
   ruby-2.5-spec:
     docker:
@@ -242,7 +219,7 @@ jobs:
       - run:
           name: Upload coverage results to Code Climate
           command: |
-            ./tmp/cc-test-reporter sum-coverage tmp/codeclimate.*.json --parts 6 --output tmp/codeclimate.total.json
+            ./tmp/cc-test-reporter sum-coverage tmp/codeclimate.*.json --parts 5 --output tmp/codeclimate.total.json
             ./tmp/cc-test-reporter upload-coverage --input tmp/codeclimate.total.json
 
   # Miscellaneous tasks
@@ -264,11 +241,6 @@ workflows:
     jobs:
       - documentation-checks
       - cc-setup
-      - ruby-2.4-spec:
-          requires:
-            - cc-setup
-      - ruby-2.4-ascii_spec
-      - ruby-2.4-rubocop
       - ruby-2.5-spec:
           requires:
             - cc-setup
@@ -302,7 +274,6 @@ workflows:
 
       - cc-upload-coverage:
           requires:
-            - ruby-2.4-spec
             - ruby-2.5-spec
             - ruby-2.6-spec
             - ruby-2.7-spec

.github/workflows/rubocop.yml

@@ -21,7 +21,7 @@ jobs:
       matrix:
         # [ ubuntu, macos, windows ]
         os: [ windows ]
-        ruby: [ '2.4', '2.5', '2.6', '2.7', '3.0', 'head' ]
+        ruby: [ '2.5', '2.6', '2.7', '3.0', 'head' ]
         include:
           - { os: windows, ruby: mingw }
         exclude:

.mergify.yml

@@ -8,7 +8,6 @@ pull_request_rules:
       - label=auto-merge
       - "#review-requested=0"
       - "#changes-requested-reviews-by=0"
-      - "status-success=windows 2.4"
       - "status-success=windows 2.5"
       - "status-success=windows 2.6"
       - "status-success=windows 2.7"
@@ -20,9 +19,6 @@ pull_request_rules:
       - "status-success=ci/circleci: jruby-9.2-ascii_spec"
       - "status-success=ci/circleci: jruby-9.2-rubocop"
       - "status-success=ci/circleci: jruby-9.2-spec"
-      - "status-success=ci/circleci: ruby-2.4-ascii_spec"
-      - "status-success=ci/circleci: ruby-2.4-rubocop"
-      - "status-success=ci/circleci: ruby-2.4-spec"
       - "status-success=ci/circleci: ruby-2.5-ascii_spec"
       - "status-success=ci/circleci: ruby-2.5-rubocop"
       - "status-success=ci/circleci: ruby-2.5-spec"

.rubocop.yml

@@ -14,7 +14,7 @@ AllCops:
     - 'tmp/**/*'
     - '.git/**/*'
     - 'bin/*'
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.5
   SuggestExtensions: false
 
 Naming/PredicateName:

Gemfile

@@ -5,13 +5,7 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'bump', require: false
-# memory_profiler 1.0.0 requires Ruby 2.5.0 or higher.
-# Please remove this branch when dropping support for Ruby 2.4.
-if RUBY_VERSION >= '2.5.0'
-  gem 'memory_profiler', platform: :mri
-else
-  gem 'memory_profiler', '<= 1.0.0', platform: :mri
-end
+gem 'memory_profiler', platform: :mri
 gem 'rake', '~> 13.0'
 gem 'rspec', '~> 3.7'
 gem 'rubocop-performance', '~> 1.10.0'

README.md

@@ -73,7 +73,7 @@ You can read a lot more about RuboCop in its [official docs](https://docs.ruboco
 
 RuboCop officially supports the following Ruby implementations:
 
-* MRI 2.4+
+* MRI 2.5+
 * JRuby 9.2+
 
 See the [compatibility documentation](https://docs.rubocop.org/rubocop/compatibility.html) for further details.

Rakefile

@@ -103,32 +103,30 @@ task documentation_syntax_check: :yard_for_generate_documentation do
     end
 
     examples.each do |example|
-      begin
-        buffer = Parser::Source::Buffer.new('<code>', 1)
-        buffer.source = example.text
-
-        # Ruby 2.6 or higher does not support a syntax used in
-        # `Lint/UselessElseWithoutRescue` cop's example.
-        parser = if cop == RuboCop::Cop::Lint::UselessElseWithoutRescue
-                   Parser::Ruby25.new(RuboCop::AST::Builder.new)
-                 # Ruby 2.7 raises a syntax error in
-                 # `Lint/CircularArgumentReference` cop's example.
-                 elsif cop == RuboCop::Cop::Lint::CircularArgumentReference
-                   Parser::Ruby26.new(RuboCop::AST::Builder.new)
-                 # Ruby 3.0 raises a syntax error in
-                 # `Lint/NumberedParameterAssignment` cop's example.
-                 elsif cop == RuboCop::Cop::Lint::NumberedParameterAssignment
-                   Parser::Ruby27.new(RuboCop::AST::Builder.new)
-                 else
-                   Parser::Ruby30.new(RuboCop::AST::Builder.new)
-                 end
-        parser.diagnostics.all_errors_are_fatal = true
-        parser.parse(buffer)
-      rescue Parser::SyntaxError => e
-        path = example.object.file
-        puts "#{path}: Syntax Error in an example. #{e}"
-        ok = false
-      end
+      buffer = Parser::Source::Buffer.new('<code>', 1)
+      buffer.source = example.text
+
+      # Ruby 2.6 or higher does not support a syntax used in
+      # `Lint/UselessElseWithoutRescue` cop's example.
+      parser = if cop == RuboCop::Cop::Lint::UselessElseWithoutRescue
+                 Parser::Ruby25.new(RuboCop::AST::Builder.new)
+               # Ruby 2.7 raises a syntax error in
+               # `Lint/CircularArgumentReference` cop's example.
+               elsif cop == RuboCop::Cop::Lint::CircularArgumentReference
+                 Parser::Ruby26.new(RuboCop::AST::Builder.new)
+               # Ruby 3.0 raises a syntax error in
+               # `Lint/NumberedParameterAssignment` cop's example.
+               elsif cop == RuboCop::Cop::Lint::NumberedParameterAssignment
+                 Parser::Ruby27.new(RuboCop::AST::Builder.new)
+               else
+                 Parser::Ruby30.new(RuboCop::AST::Builder.new)
+               end
+      parser.diagnostics.all_errors_are_fatal = true
+      parser.parse(buffer)
+    rescue Parser::SyntaxError => e
+      path = example.object.file
+      puts "#{path}: Syntax Error in an example. #{e}"
+      ok = false
     end
   end
   abort unless ok

changelog/change_drop_ruby_24.md

@@ -0,0 +1 @@
+* [#9647](https://github.com/rubocop/rubocop/pull/9647): Drop support for Ruby 2.4. ([@koic][])

docs/modules/ROOT/pages/compatibility.adoc

@@ -1,10 +1,10 @@
 = Compatibility
 
-RuboCop targets Ruby 2.4+.footnote:[As defined by its reference implementation MRI.]
+RuboCop targets Ruby 2.5+.footnote:[As defined by its reference implementation MRI.]
 
 RuboCop officially supports MRI (a.k.a. CRuby) and JRuby.
 
-- MRI 2.4+
+- MRI 2.5+
 - JRuby 9.2+
 
 The oldest supported JRuby version is derived from the oldest compatible MRI version.
@@ -14,7 +14,7 @@ NOTE: RuboCop might be working with other Ruby implementations as well, but it's
 == Support Matrix
 
 RuboCop generally aims to follow MRI's own support policy - meaning RuboCop would support all officially supported MRI releases.footnote:[Typically the last 3 releases.] To give people extra time for a smooth transition, we've customarily provided support for about one year after EOL of MRI version.
-This means that if Ruby 2.4 reaches its EOL in Spring 2020, it would be supported by RuboCop (at least) until Spring 2021.footnote:[At the core team's discretion this policy might be waived aside for MRI releases causing significant maintenance overhead.]
+This means that if Ruby 2.5 reaches its EOL in Spring 2021, it would be supported by RuboCop (at least) until Spring 2022.footnote:[At the core team's discretion this policy might be waived aside for MRI releases causing significant maintenance overhead.]
 
 The following table is the support matrix.
 
@@ -26,7 +26,7 @@ The following table is the support matrix.
 | 2.1 | 0.57
 | 2.2 | 0.68
 | 2.3 | 0.81
-| 2.4 | -
+| 2.4 | 1.12
 | 2.5 | -
 | 2.6 | -
 | 2.7 | -

docs/modules/ROOT/pages/formatters.adoc

@@ -205,11 +205,11 @@ The JSON structure is like the following example:
 ----
 {
   "metadata": {
-    "rubocop_version": "0.50.0",
+    "rubocop_version": "1.12.0",
     "ruby_engine": "ruby",
-    "ruby_version": "2.4.2",
-    "ruby_patchlevel": "198",
-    "ruby_platform": "x86_64-darwin12.3.0"
+    "ruby_version": "3.0.0",
+    "ruby_patchlevel": "0",
+    "ruby_platform": "x86_64-darwin19"
   },
   "files": [{
       "path": "lib/foo.rb",

lib/rubocop.rb

@@ -18,7 +18,6 @@
 require_relative 'rubocop/ext/regexp_parser'
 
 require_relative 'rubocop/core_ext/string'
-require_relative 'rubocop/core_ext/hash'
 require_relative 'rubocop/ext/processed_source'
 
 require_relative 'rubocop/path_util'

lib/rubocop/comment_config.rb

@@ -32,9 +32,7 @@ def extra_enabled_comments
     end
 
     def comment_only_line?(line_number)
-      non_comment_token_line_numbers.none? do |non_comment_line_number|
-        non_comment_line_number == line_number
-      end
+      non_comment_token_line_numbers.none?(line_number)
     end
 
     private

lib/rubocop/cop/generator/require_file_injector.rb

@@ -29,9 +29,7 @@ def inject
         attr_reader :require_entries, :root_file_path, :source_path, :output
 
         def require_exists?
-          require_entries.any? do |entry|
-            entry == injectable_require_directive
-          end
+          require_entries.any?(injectable_require_directive)
         end
 
         def updated_directives

lib/rubocop/cop/lint/shadowed_exception.rb

@@ -111,14 +111,12 @@ def evaluate_exceptions(group)
 
           if rescued_exceptions.any?
             rescued_exceptions.each_with_object([]) do |exception, converted|
-              begin
-                RuboCop::Util.silence_warnings do
-                  # Avoid printing deprecation warnings about constants
-                  converted << Kernel.const_get(exception.source)
-                end
-              rescue NameError
-                converted << nil
+              RuboCop::Util.silence_warnings do
+                # Avoid printing deprecation warnings about constants
+                converted << Kernel.const_get(exception.source)
               end
+            rescue NameError
+              converted << nil
             end
           else
             # treat an empty `rescue` as `rescue StandardError`

lib/rubocop/cop/lint/symbol_conversion.rb

@@ -152,7 +152,7 @@ def correct_hash_key(node)
           # will be ignored.
           return unless node.value.to_s.match?(/\A[a-z0-9_]/i)
 
-          correction = node.value.inspect.gsub(/\A:/, '')
+          correction = node.value.inspect.delete_prefix(':')
           return if properly_quoted?(node.source, correction)
 
           register_offense(

lib/rubocop/cop/mixin/method_preference.rb

@@ -18,8 +18,7 @@ def preferred_methods
             default = default_cop_config['PreferredMethods']
             merged = cop_config['PreferredMethods']
             overrides = merged.values - default.values
-            merged.reject { |key, _| overrides.include?(key) }
-                  .map { |k, v| [k.to_sym, v] }.to_h
+            merged.reject { |key, _| overrides.include?(key) }.transform_keys(&:to_sym)
           end
       end
 

lib/rubocop/cop/naming/memoized_instance_variable_name.rb

@@ -260,7 +260,7 @@ def suggested_var(method_name)
         end
 
         def variable_name_candidates(method_name)
-          no_underscore = method_name.sub(/\A_/, '')
+          no_underscore = method_name.delete_prefix('_')
           with_underscore = "_#{method_name}"
           case style
           when :required

lib/rubocop/cop/style/hash_syntax.rb

@@ -137,7 +137,7 @@ def word_symbol_pair?(pair)
         end
 
         def acceptable_19_syntax_symbol?(sym_name)
-          sym_name.sub!(/\A:/, '')
+          sym_name.delete_prefix!(':')
 
           if cop_config['PreferHashRocketsForNonAlnumEndingSymbols'] &&
              # Prefer { :production? => false } over { production?: false } and

lib/rubocop/cop/style/multiple_comparison.rb

@@ -142,7 +142,7 @@ def root_of_or_node(or_node)
         def switch_comparison?(node)
           return true if @last_comparison.nil?
 
-          @last_comparison.descendants.none? { |descendant| descendant == node }
+          @last_comparison.descendants.none?(node)
         end
 
         def reset_comparison

lib/rubocop/cop/style/nested_ternary_operator.rb

@@ -51,7 +51,7 @@ def if_node(node)
         def remove_parentheses(source)
           return source unless source.start_with?('(')
 
-          source.gsub(/\A\(/, '').gsub(/\)\z/, '')
+          source.delete_prefix('(').delete_suffix(')')
         end
       end
     end

lib/rubocop/cop/style/parallel_assignment.rb

@@ -164,9 +164,7 @@ def dependency?(lhs, rhs)
           # Does `rhs` access the same value which is assigned by `lhs`?
           def accesses?(rhs, lhs)
             if lhs.method?(:[]=)
-              matching_calls(rhs, lhs.receiver, :[]).any? do |args|
-                args == lhs.arguments
-              end
+              matching_calls(rhs, lhs.receiver, :[]).any?(lhs.arguments)
             else
               access_method = lhs.method_name.to_s.chop.to_sym
               matching_calls(rhs, lhs.receiver, access_method).any?

lib/rubocop/cop/style/redundant_begin.rb

@@ -36,7 +36,6 @@ module Style
       #   do_something
       #
       #   # bad
-      #   # When using Ruby 2.5 or later.
       #   do_something do
       #     begin
       #       something
@@ -76,8 +75,6 @@ def on_def(node)
         alias on_defs on_def
 
         def on_block(node)
-          return if target_ruby_version < 2.5
-
           return if node.send_node.lambda_literal?
           return if node.braces?
           return unless node.body&.kwbegin_type?

lib/rubocop/cop/style/redundant_file_extension_in_require.rb

@@ -40,7 +40,7 @@ def on_send(node)
             return unless name_node.value.end_with?('.rb')
 
             add_offense(name_node) do |corrector|
-              correction = name_node.value.sub(/\.rb\z/, '')
+              correction = name_node.value.delete_suffix('.rb')
 
               corrector.replace(name_node, "'#{correction}'")
             end

lib/rubocop/cop/style/redundant_return.rb

@@ -73,7 +73,7 @@ def correct_with_arguments(return_node, corrector)
           end
           if return_node.splat_argument?
             first_argument = return_node.first_argument
-            corrector.replace(first_argument, first_argument.source.gsub(/\A\*/, ''))
+            corrector.replace(first_argument, first_argument.source.delete_prefix('*'))
           end
 
           keyword = range_with_surrounding_space(range: return_node.loc.keyword,

lib/rubocop/cop/style/unless_logical_operators.rb

@@ -90,14 +90,14 @@ def mixed_precedence_and?(node)
           and_sources = node.condition.each_descendant(:and).map(&:operator)
           and_sources << node.condition.operator if node.condition.and_type?
 
-          !(and_sources.all? { |s| s == '&&' } || and_sources.all? { |s| s == 'and' })
+          !(and_sources.all?('&&') || and_sources.all?('and'))
         end
 
         def mixed_precedence_or?(node)
           or_sources = node.condition.each_descendant(:or).map(&:operator)
           or_sources << node.condition.operator if node.condition.or_type?
 
-          !(or_sources.all? { |s| s == '||' } || or_sources.all? { |s| s == 'or' })
+          !(or_sources.all?('||') || or_sources.all?('or'))
         end
       end
     end