Merge pull request rails#32971 from y-yagi/use_plus_operator_to_unfreeze_string

Enable `Performance/UnfreezeString` cop

Author: y-yagi

.rubocop.yml

@@ -208,3 +208,6 @@ Performance/EndWith:
 
 Performance/RegexpMatch:
   Enabled: true
+
+Performance/UnfreezeString:
+  Enabled: true

actioncable/lib/action_cable/channel/base.rb

@@ -270,7 +270,7 @@ def dispatch_action(action, data)
         end
 
         def action_signature(action, data)
-          "#{self.class.name}##{action}".dup.tap do |signature|
+          (+"#{self.class.name}##{action}").tap do |signature|
             if (arguments = data.except("action")).any?
               signature << "(#{arguments.inspect})"
             end

actionmailer/test/base_test.rb

@@ -122,7 +122,7 @@ class BaseTest < ActiveSupport::TestCase
     email = BaseMailer.attachment_with_hash
     assert_equal(1, email.attachments.length)
     assert_equal("invoice.jpg", email.attachments[0].filename)
-    expected = "\312\213\254\232)b".dup
+    expected = +"\312\213\254\232)b"
     expected.force_encoding(Encoding::BINARY)
     assert_equal expected, email.attachments["invoice.jpg"].decoded
   end
@@ -131,7 +131,7 @@ class BaseTest < ActiveSupport::TestCase
     email = BaseMailer.attachment_with_hash_default_encoding
     assert_equal(1, email.attachments.length)
     assert_equal("invoice.jpg", email.attachments[0].filename)
-    expected = "\312\213\254\232)b".dup
+    expected = +"\312\213\254\232)b"
     expected.force_encoding(Encoding::BINARY)
     assert_equal expected, email.attachments["invoice.jpg"].decoded
   end

actionpack/lib/action_controller/log_subscriber.rb

@@ -26,7 +26,7 @@ def process_action(event)
           exception_class_name = payload[:exception].first
           status = ActionDispatch::ExceptionWrapper.status_code_for_exception(exception_class_name)
         end
-        message = "Completed #{status} #{Rack::Utils::HTTP_STATUS_CODES[status]} in #{event.duration.round}ms".dup
+        message = +"Completed #{status} #{Rack::Utils::HTTP_STATUS_CODES[status]} in #{event.duration.round}ms"
         message << " (#{additions.join(" | ".freeze)})" unless additions.empty?
         message << "\n\n" if defined?(Rails.env) && Rails.env.development?
 

actionpack/lib/action_controller/metal/http_authentication.rb

@@ -474,7 +474,7 @@ def params_array_from(raw_params)
 
       # This removes the <tt>"</tt> characters wrapping the value.
       def rewrite_param_values(array_params)
-        array_params.each { |param| (param[1] || "".dup).gsub! %r/^"|"$/, "" }
+        array_params.each { |param| (param[1] || +"").gsub! %r/^"|"$/, "" }
       end
 
       # This method takes an authorization body and splits up the key-value

actionpack/lib/action_controller/metal/live.rb

@@ -297,7 +297,7 @@ def log_error(exception)
       return unless logger
 
       logger.fatal do
-        message = "\n#{exception.class} (#{exception.message}):\n".dup
+        message = +"\n#{exception.class} (#{exception.message}):\n"
         message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
         message << "  " << exception.backtrace.join("\n  ")
         "#{message}\n\n"

actionpack/lib/action_controller/metal/rendering.rb

@@ -40,7 +40,7 @@ def render(*args) #:nodoc:
     def render_to_string(*)
       result = super
       if result.respond_to?(:each)
-        string = "".dup
+        string = +""
         result.each { |r| string << r }
         string
       else

actionpack/lib/action_dispatch/http/response.rb

@@ -105,7 +105,7 @@ def initialize(response, buf)
 
       def body
         @str_body ||= begin
-          buf = "".dup
+          buf = +""
           each { |chunk| buf << chunk }
           buf
         end

actionpack/lib/action_dispatch/http/url.rb

@@ -157,7 +157,7 @@ def normalize_host(_host, options)
           subdomain  = options.fetch :subdomain, true
           domain     = options[:domain]
 
-          host = "".dup
+          host = +""
           if subdomain == true
             return _host if domain.nil?
 

actionpack/lib/action_dispatch/journey/formatter.rb

@@ -50,7 +50,7 @@ def generate(name, options, path_parameters, parameterize = nil)
         unmatched_keys = (missing_keys || []) & constraints.keys
         missing_keys = (missing_keys || []) - unmatched_keys
 
-        message = "No route matches #{Hash[constraints.sort_by { |k, v| k.to_s }].inspect}".dup
+        message = +"No route matches #{Hash[constraints.sort_by { |k, v| k.to_s }].inspect}"
         message << ", missing required keys: #{missing_keys.sort.inspect}" if missing_keys && !missing_keys.empty?
         message << ", possible unmatched constraints: #{unmatched_keys.sort.inspect}" if unmatched_keys && !unmatched_keys.empty?