[Fix #8256] Fix an error for --auto-gen-config when running a cop without autocorrect

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#8252](https://github.com/rubocop-hq/rubocop/issues/8252): Fix a command line option name from `--safe-autocorrect` to `--safe-auto-correct`, which is compatible with RuboCop 0.86 and lower. ([@koic][])
 * [#8239](https://github.com/rubocop-hq/rubocop/pull/8239): Don't load `.rubocop.yml` from personal folders to check for exclusions if given a custom configuration file. ([@deivid-rodriguez][])
+* [#8256](https://github.com/rubocop-hq/rubocop/issues/8256): Fix an error for `--auto-gen-config` when running a cop who do not support auto-correction. ([@koic][])
 
 ## 0.87.0 (2020-07-06)
 

lib/rubocop/formatter/disabled_config_formatter.rb

@@ -115,7 +115,7 @@ def output_cop_comments(output_buffer, cfg, cop_name, offense_count)
         output_buffer.puts "# Offense count: #{offense_count}" if @show_offense_counts
 
         cop_class = Cop::Cop.registry.find_by_cop_name(cop_name)
-        output_buffer.puts '# Cop supports --auto-correct.' if cop_class&.new&.support_autocorrect?
+        output_buffer.puts '# Cop supports --auto-correct.' if cop_class&.support_autocorrect?
 
         default_cfg = default_config(cop_name)
         return unless default_cfg

spec/rubocop/cli/cli_auto_gen_config_spec.rb

@@ -441,6 +441,47 @@ def f
       end
     end
 
+    context 'when working with a cop who do not support auto-correction' do
+      it 'can generate a todo list' do
+        create_file('example1.rb', <<~RUBY)
+          def fooBar; end
+        RUBY
+        create_file('.rubocop.yml', <<~YAML)
+          # The following cop does not support auto-correction.
+          Naming/MethodName:
+            Enabled: true
+        YAML
+        expect(cli.run(%w[--auto-gen-config])).to eq(0)
+        expect($stderr.string).to eq('')
+        # expect($stdout.string).to include('Created .rubocop_todo.yml.')
+        expect(Dir['.*']).to include('.rubocop_todo.yml')
+        todo_contents = IO.read('.rubocop_todo.yml').lines[8..-1].join
+        expect(todo_contents).to eq(<<~YAML)
+          # Offense count: 1
+          # Configuration parameters: EnforcedStyle, IgnoredPatterns.
+          # SupportedStyles: snake_case, camelCase
+          Naming/MethodName:
+            Exclude:
+              - 'example1.rb'
+
+          # Offense count: 1
+          # Cop supports --auto-correct.
+          # Configuration parameters: EnforcedStyle.
+          # SupportedStyles: always, always_true, never
+          Style/FrozenStringLiteralComment:
+            Exclude:
+              - 'example1.rb'
+        YAML
+        expect(IO.read('.rubocop.yml')).to eq(<<~YAML)
+          inherit_from: .rubocop_todo.yml
+
+          # The following cop does not support auto-correction.
+          Naming/MethodName:
+            Enabled: true
+        YAML
+      end
+    end
+
     context 'when working in a subdirectory' do
       it 'can generate a todo list' do
         create_file('dir/example1.rb', ['$x = 0 ',