Required ruby version fixes (rubocop#9515)

- Create `Gem::Requirement` from required_ruby_version
- Return first `KNOWN_RUBY` that satisfies the requirement when one exists
- Support more types of version entries

changelog/fix_return_minimal_known_ruby_version_from.md

@@ -0,0 +1 @@
+* [#9482](https://github.com/rubocop-hq/rubocop/issues/9482): Return minimal known ruby version from gemspecs `required_ruby_version`. ([@HeroProtagonist][])

lib/rubocop/target_ruby.rb

@@ -165,14 +165,10 @@ def find_version
         file = gemspec_filepath
         return unless file && File.file?(file)
 
-        version = version_from_gemspec_file(file)
-        return if version.nil?
+        right_hand_side = version_from_gemspec_file(file)
+        return if right_hand_side.nil?
 
-        requirement = version.children.last
-        return version_from_array(version) if version.array_type?
-        return version_from_array(requirement) if gem_requirement? version
-
-        version_from_str(version.str_content)
+        find_minimal_known_ruby(right_hand_side)
       end
 
       def gemspec_filename
@@ -192,15 +188,25 @@ def version_from_gemspec_file(file)
         required_ruby_version(processed_source.ast).first
       end
 
+      def version_from_right_hand_side(right_hand_side)
+        if right_hand_side.array_type?
+          version_from_array(right_hand_side)
+        elsif gem_requirement?(right_hand_side)
+          right_hand_side.children.last.value
+        else
+          right_hand_side.value
+        end
+      end
+
       def version_from_array(array)
-        versions = array.children.map { |v| version_from_str(v.is_a?(String) ? v : v.str_content) }
-        versions.compact.min
+        array.children.map(&:value)
       end
 
-      def version_from_str(str)
-        str.match(/^(?:>=|<=)?\s*(?<version>\d+(?:\.\d+)*)/) do |md|
-          md[:version].to_f
-        end
+      def find_minimal_known_ruby(right_hand_side)
+        version = version_from_right_hand_side(right_hand_side)
+        requirement = Gem::Requirement.new(version)
+
+        KNOWN_RUBIES.detect { |v| requirement.satisfied_by?(Gem::Version.new("#{v}.99")) }
       end
     end
 

spec/rubocop/target_ruby_spec.rb

@@ -294,82 +294,68 @@
           let(:base_path) { configuration.base_dir_for_path_parameters }
           let(:gemspec_file_path) { File.join(base_path, 'example.gemspec') }
 
-          it 'sets target_ruby from required_ruby_version from exact version' do
+          it 'sets target_ruby from inclusive range' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
                   s.name = 'test'
-                  s.required_ruby_version = '2.7.4'
+                  s.required_ruby_version = '>= 2.6.1'
                   s.licenses = ['MIT']
                 end
               HEREDOC
 
             create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq 2.7
+            expect(target_ruby.version).to eq 2.6
           end
 
-          it 'sets target_ruby from required_ruby_version from inclusive range' do
+          it 'sets target_ruby from exclusive range' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
                   s.name = 'test'
-                  s.required_ruby_version = '>= 3.0.0'
+                  s.required_ruby_version = '> 2.4.1'
                   s.licenses = ['MIT']
                 end
               HEREDOC
 
             create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq 3.0
+            expect(target_ruby.version).to eq 2.4
           end
 
-          it 'sets default target_ruby from exclusive range' do
+          it 'sets target_ruby from approximate version' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
                   s.name = 'test'
-                  s.required_ruby_version = '< 3.0.0'
+                  s.required_ruby_version = '~> 2.5.0'
                   s.licenses = ['MIT']
                 end
               HEREDOC
 
             create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq default_version
+            expect(target_ruby.version).to eq 2.5
           end
         end
 
         context 'when file contains `required_ruby_version` as a requirement' do
           let(:base_path) { configuration.base_dir_for_path_parameters }
           let(:gemspec_file_path) { File.join(base_path, 'example.gemspec') }
 
-          it 'sets target_ruby from required_ruby_version from exact requirement version' do
-            content =
-              <<-HEREDOC
-                Gem::Specification.new do |s|
-                  s.name = 'test'
-                  s.required_ruby_version = Gem::Requirement.new('2.7.4')
-                  s.licenses = ['MIT']
-                end
-              HEREDOC
-
-            create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq 2.7
-          end
-
           it 'sets target_ruby from required_ruby_version from inclusive requirement range' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
                   s.name = 'test'
-                  s.required_ruby_version = Gem::Requirement.new('>= 3.0.0')
+                  s.required_ruby_version = Gem::Requirement.new('>= 2.3.1')
                   s.licenses = ['MIT']
                 end
               HEREDOC
 
             create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq 3.0
+            expect(target_ruby.version).to eq default_version
           end
 
-          it 'sets default target_ruby from exclusive requirement range' do
+          it 'sets first known ruby version that satisfies requirement' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
@@ -388,7 +374,7 @@
           let(:base_path) { configuration.base_dir_for_path_parameters }
           let(:gemspec_file_path) { File.join(base_path, 'example.gemspec') }
 
-          it 'sets target_ruby from the lowest value' do
+          it 'sets target_ruby to the minimal version satisfying the requirements' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
@@ -402,32 +388,18 @@
             expect(target_ruby.version).to eq 2.6
           end
 
-          it 'sets target_ruby from required_ruby_version with inclusive range' do
+          it 'sets target_ruby from required_ruby_version with many requirements' do
             content =
               <<-HEREDOC
                 Gem::Specification.new do |s|
                   s.name = 'test'
-                  s.required_ruby_version = ['<=2.7.4', '>2.6.5']
+                  s.required_ruby_version = ['<=2.7.4', '>2.4.5', '~>2.5.1']
                   s.licenses = ['MIT']
                 end
               HEREDOC
 
             create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq 2.7
-          end
-
-          it 'sets default target_ruby with all exclusive ranges' do
-            content =
-              <<-HEREDOC
-                Gem::Specification.new do |s|
-                  s.name = 'test'
-                  s.required_ruby_version = ['<2.7.4', '>2.6.5']
-                  s.licenses = ['MIT']
-                end
-              HEREDOC
-
-            create_file(gemspec_file_path, content)
-            expect(target_ruby.version).to eq default_version
+            expect(target_ruby.version).to eq 2.5
           end
         end