Recover Ruby 2.3 code analysis using TargetRubyVersion: 2.3

Follow up rubocop#10632 (comment).

Reverts part of rubocop#7869 and rubocop#8056.

Only the Ruby version (2.3) to runtime should have been dropped, not
code analysis.
This PR makes Ruby 2.3 code analysis with `TargetRubyVersion: 2.3`.
It aims to solve essentially the same problem as rubocop#10626 and 10632.

And this change requires RuboCop AST 1.18 or later:
rubocop/rubocop-ast#233

changelog/fix_recover_ruby_23_code_analysis.md

@@ -0,0 +1 @@
+* [#10640](https://github.com/rubocop/rubocop/pull/10640): Recover Ruby 2.3 code analysis using `TargetRubyVersion: 2.3`. ([@koic][])

lib/rubocop/cop/lint/unified_integer.rb

@@ -33,6 +33,8 @@ def on_const(node)
           return unless klass
 
           add_offense(node, message: format(MSG, klass: klass)) do |corrector|
+            next if target_ruby_version <= 2.3
+
             corrector.replace(node.loc.name, 'Integer')
           end
         end

lib/rubocop/cop/style/hash_transform_values.rb

@@ -26,6 +26,9 @@ module Style
       class HashTransformValues < Base
         include HashTransformMethod
         extend AutoCorrector
+        extend TargetRubyVersion
+
+        minimum_target_ruby_version 2.4
 
         # @!method on_bad_each_with_object(node)
         def_node_matcher :on_bad_each_with_object, <<~PATTERN

lib/rubocop/cop/style/unpack_first.rb

@@ -19,6 +19,9 @@ module Style
       #
       class UnpackFirst < Base
         extend AutoCorrector
+        extend TargetRubyVersion
+
+        minimum_target_ruby_version 2.4
 
         MSG = 'Use `%<receiver>s.unpack1(%<format>s)` instead of '\
               '`%<receiver>s.unpack(%<format>s)%<method>s`.'

lib/rubocop/rspec/shared_contexts.rb

@@ -116,6 +116,10 @@ def source_range(range, buffer: source_buffer)
   end
 end
 
+RSpec.shared_context 'ruby 2.3', :ruby23 do
+  let(:ruby_version) { 2.3 }
+end
+
 RSpec.shared_context 'ruby 2.4', :ruby24 do
   let(:ruby_version) { 2.4 }
 end

lib/rubocop/target_ruby.rb

@@ -4,7 +4,7 @@ module RuboCop
   # The kind of Ruby that code inspected by RuboCop is written in.
   # @api private
   class TargetRuby
-    KNOWN_RUBIES = [2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2].freeze
+    KNOWN_RUBIES = [2.3, 2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2].freeze
     DEFAULT_VERSION = 2.6
 
     OBSOLETE_RUBIES = {

rubocop.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency('rainbow', '>= 2.2.2', '< 4.0')
   s.add_runtime_dependency('regexp_parser', '>= 1.8', '< 3.0')
   s.add_runtime_dependency('rexml', '>= 3.2.5', '< 4.0')
-  s.add_runtime_dependency('rubocop-ast', '>= 1.17.0', '< 2.0')
+  s.add_runtime_dependency('rubocop-ast', '>= 1.18.0', '< 2.0')
   s.add_runtime_dependency('ruby-progressbar', '~> 1.7')
   s.add_runtime_dependency('unicode-display_width', '>= 1.4.0', '< 3.0')
 

spec/rubocop/cli_spec.rb

@@ -1724,7 +1724,7 @@ def method(foo, bar, qux, fred, arg5, f) end #{'#' * 85}
           'Error: RuboCop found unknown Ruby version 4.0 in `TargetRubyVersion`'
         )
         expect($stderr.string.strip).to match(
-          /Supported versions: 2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2/
+          /Supported versions: 2.3, 2.4, 2.5, 2.6, 2.7, 3.0, 3.1, 3.2/
         )
       end
     end
@@ -1746,7 +1746,7 @@ def method(foo, bar, qux, fred, arg5, f) end #{'#' * 85}
           /2\.0-compatible analysis was dropped after version 0\.50/
         )
 
-        expect($stderr.string.strip).to match(/Supported versions: 2.4/)
+        expect($stderr.string.strip).to match(/Supported versions: 2.3/)
       end
     end
   end

spec/rubocop/config_loader_spec.rb

@@ -1188,7 +1188,7 @@ class Loop < Base
       end
 
       context 'when the specified version is obsolete' do
-        let(:inherited_version) { '2.3' }
+        let(:inherited_version) { '2.2' }
 
         context 'and it is not overridden' do
           before do
@@ -1199,7 +1199,7 @@ class Loop < Base
 
           it 'raises a validation error' do
             expect { configuration_from_file }.to raise_error(RuboCop::ValidationError) do |error|
-              expect(error.message).to start_with('RuboCop found unsupported Ruby version 2.3')
+              expect(error.message).to start_with('RuboCop found unsupported Ruby version 2.2')
             end
           end
         end

spec/rubocop/cop/lint/unified_integer_spec.rb

@@ -2,36 +2,72 @@
 
 RSpec.describe RuboCop::Cop::Lint::UnifiedInteger, :config do
   shared_examples 'registers an offense' do |klass|
-    context "when #{klass}" do
-      context 'without any decorations' do
-        it 'registers an offense and autocorrects' do
-          expect_offense(<<~RUBY, klass: klass)
-            1.is_a?(%{klass})
-                    ^{klass} Use `Integer` instead of `#{klass}`.
-          RUBY
-
-          expect_correction(<<~RUBY)
-            1.is_a?(Integer)
-          RUBY
+    context 'target ruby version < 2.4', :ruby23 do
+      context "when #{klass}" do
+        context 'without any decorations' do
+          it 'registers an offense and autocorrects' do
+            expect_offense(<<~RUBY, klass: klass)
+              1.is_a?(%{klass})
+                      ^{klass} Use `Integer` instead of `#{klass}`.
+            RUBY
+
+            expect_no_corrections
+          end
         end
-      end
 
-      context 'when explicitly specified as toplevel constant' do
-        it 'registers an offense' do
-          expect_offense(<<~RUBY, klass: klass)
-            1.is_a?(::%{klass})
-                    ^^^{klass} Use `Integer` instead of `#{klass}`.
-          RUBY
+        context 'when explicitly specified as toplevel constant' do
+          let(:source) { "1.is_a?(::#{klass})" }
+
+          it 'registers an offense' do
+            expect_offense(<<~RUBY, klass: klass)
+              1.is_a?(::%{klass})
+                      ^^^{klass} Use `Integer` instead of `#{klass}`.
+            RUBY
 
-          expect_correction(<<~RUBY)
-            1.is_a?(::Integer)
-          RUBY
+            expect_no_corrections
+          end
+        end
+
+        context 'with MyNamespace' do
+          it 'does not register an offense' do
+            expect_no_offenses("1.is_a?(MyNamespace::#{klass})")
+          end
         end
       end
+    end
+
+    context 'target ruby version >= 2.4', :ruby24 do
+      context "when #{klass}" do
+        context 'without any decorations' do
+          it 'registers an offense' do
+            expect_offense(<<~RUBY, klass: klass)
+              1.is_a?(#{klass})
+                      ^{klass} Use `Integer` instead of `#{klass}`.
+            RUBY
+
+            expect_correction(<<~RUBY)
+              1.is_a?(Integer)
+            RUBY
+          end
+        end
+
+        context 'when explicitly specified as toplevel constant' do
+          it 'registers an offense' do
+            expect_offense(<<~RUBY, klass: klass)
+              1.is_a?(::#{klass})
+                      ^^^{klass} Use `Integer` instead of `#{klass}`.
+            RUBY
+
+            expect_correction(<<~RUBY)
+              1.is_a?(::Integer)
+            RUBY
+          end
+        end
 
-      context 'with MyNamespace' do
-        it 'does not register an offense' do
-          expect_no_offenses("1.is_a?(MyNamespace::#{klass})")
+        context 'with MyNamespace' do
+          it 'does not register an offense' do
+            expect_no_offenses("1.is_a?(MyNamespace::#{klass})")
+          end
         end
       end
     end