Merge pull request #32971 from y-yagi/use_plus_operator_to_unfreeze_s…

…tring

Enable `Performance/UnfreezeString` cop

.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?
 

actionpack/lib/action_dispatch/journey/router/utils.rb

@@ -17,11 +17,11 @@ class Utils # :nodoc:
         def self.normalize_path(path)
           path ||= ""
           encoding = path.encoding
-          path = "/#{path}".dup
+          path = +"/#{path}"
           path.squeeze!("/".freeze)
           path.sub!(%r{/+\Z}, "".freeze)
           path.gsub!(/(%[a-f0-9]{2})/) { $1.upcase }
-          path = "/".dup if path == "".freeze
+          path = +"/" if path == "".freeze
           path.force_encoding(encoding)
           path
         end
@@ -32,7 +32,7 @@ class UriEncoder # :nodoc:
           ENCODE   = "%%%02X".freeze
           US_ASCII = Encoding::US_ASCII
           UTF_8    = Encoding::UTF_8
-          EMPTY    = "".dup.force_encoding(US_ASCII).freeze
+          EMPTY    = (+"").force_encoding(US_ASCII).freeze
           DEC2HEX  = (0..255).to_a.map { |i| ENCODE % i }.map { |s| s.force_encoding(US_ASCII) }
 
           ALPHA = "a-zA-Z".freeze

actionpack/lib/action_dispatch/middleware/debug_exceptions.rb

@@ -23,7 +23,7 @@ def debug_params(params)
         if clean_params.empty?
           "None"
         else
-          PP.pp(clean_params, "".dup, 200)
+          PP.pp(clean_params, +"", 200)
         end
       end
 

actionpack/lib/action_dispatch/middleware/debug_locks.rb

@@ -63,19 +63,19 @@ def render_details(req)
 
         str = threads.map do |thread, info|
           if info[:exclusive]
-            lock_state = "Exclusive".dup
+            lock_state = +"Exclusive"
           elsif info[:sharing] > 0
-            lock_state = "Sharing".dup
+            lock_state = +"Sharing"
             lock_state << " x#{info[:sharing]}" if info[:sharing] > 1
           else
-            lock_state = "No lock".dup
+            lock_state = +"No lock"
           end
 
           if info[:waiting]
             lock_state << " (yielded share)"
           end
 
-          msg = "Thread #{info[:index]} [0x#{thread.__id__.to_s(16)} #{thread.status || 'dead'}]  #{lock_state}\n".dup
+          msg = +"Thread #{info[:index]} [0x#{thread.__id__.to_s(16)} #{thread.status || 'dead'}]  #{lock_state}\n"
 
           if info[:sleeper]
             msg << "  Waiting in #{info[:sleeper]}"

actionpack/lib/action_dispatch/middleware/ssl.rb

@@ -102,7 +102,7 @@ def normalize_hsts_options(options)
 
       # https://tools.ietf.org/html/rfc6797#section-6.1
       def build_hsts_header(hsts)
-        value = "max-age=#{hsts[:expires].to_i}".dup
+        value = +"max-age=#{hsts[:expires].to_i}"
         value << "; includeSubDomains" if hsts[:subdomains]
         value << "; preload" if hsts[:preload]
         value
@@ -141,7 +141,7 @@ def https_location_for(request)
         host = @redirect[:host] || request.host
         port = @redirect[:port] || request.port
 
-        location = "https://#{host}".dup
+        location = +"https://#{host}"
         location << ":#{port}" if port != 80 && port != 443
         location << request.fullpath
         location

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -308,7 +308,7 @@ def app(blocks)
           def check_controller_and_action(path_params, controller, action)
             hash = check_part(:controller, controller, path_params, {}) do |part|
               translate_controller(part) {
-                message = "'#{part}' is not a supported controller name. This can lead to potential routing problems.".dup
+                message = +"'#{part}' is not a supported controller name. This can lead to potential routing problems."
                 message << " See https://guides.rubyonrails.org/routing.html#specifying-a-controller-to-use"
 
                 raise ArgumentError, message

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -245,7 +245,7 @@ def raise_generation_error(args)
                   missing_keys << missing_key
                 }
                 constraints = Hash[@route.requirements.merge(params).sort_by { |k, v| k.to_s }]
-                message = "No route matches #{constraints.inspect}".dup
+                message = +"No route matches #{constraints.inspect}"
                 message << ", missing required keys: #{missing_keys.sort.inspect}"
 
                 raise ActionController::UrlGenerationError, message

actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb

@@ -65,7 +65,7 @@ def output_type
           end
 
           def display_image
-            message = "[Screenshot]: #{image_path}\n".dup
+            message = +"[Screenshot]: #{image_path}\n"
 
             case output_type
             when "artifact"

actionpack/lib/action_dispatch/testing/assertions/response.rb

@@ -79,9 +79,8 @@ def normalize_argument_to_redirection(fragment)
         end
 
         def generate_response_message(expected, actual = @response.response_code)
-          "Expected response to be a <#{code_with_name(expected)}>,"\
-          " but was a <#{code_with_name(actual)}>"
-            .dup.concat(location_if_redirected).concat(response_body_if_short)
+          (+"Expected response to be a <#{code_with_name(expected)}>,"\
+          " but was a <#{code_with_name(actual)}>").concat(location_if_redirected).concat(response_body_if_short)
         end
 
         def response_body_if_short

actionpack/test/controller/http_token_authentication_test.rb

@@ -150,7 +150,7 @@ def authenticate_long_credentials
   end
 
   test "token_and_options returns empty string with empty token" do
-    token = "".dup
+    token = +""
     actual = ActionController::HttpAuthentication::Token.token_and_options(sample_request(token)).first
     expected = token
     assert_equal(expected, actual)

actionpack/test/controller/new_base/bare_metal_test.rb

@@ -13,7 +13,7 @@ class BareTest < ActiveSupport::TestCase
     test "response body is a Rack-compatible response" do
       status, headers, body = BareController.action(:index).call(Rack::MockRequest.env_for("/"))
       assert_equal 200, status
-      string = "".dup
+      string = +""
 
       body.each do |part|
         assert part.is_a?(String), "Each part of the body must be a String"

actionpack/test/controller/routing_test.rb

@@ -674,7 +674,7 @@ def test_route_with_text_default
     assert_equal "/page/foo", url_for(rs, controller: "content", action: "show_page", id: "foo")
     assert_equal({ controller: "content", action: "show_page", id: "foo" }, rs.recognize_path("/page/foo"))
 
-    token = "\321\202\320\265\320\272\321\201\321\202".dup # 'text' in Russian
+    token = +"\321\202\320\265\320\272\321\201\321\202" # 'text' in Russian
     token.force_encoding(Encoding::BINARY)
     escaped_token = CGI.escape(token)
 

actionpack/test/dispatch/debug_exceptions_test.rb

@@ -368,7 +368,7 @@ def call(env)
     })
     assert_response 500
 
-    assert_includes(body, CGI.escapeHTML(PP.pp(params, "".dup, 200)))
+    assert_includes(body, CGI.escapeHTML(PP.pp(params, +"", 200)))
   end
 
   test "sets the HTTP charset parameter" do

actionpack/test/dispatch/prefix_generation_test.rb

@@ -13,7 +13,7 @@ def to_param
     end
 
     def self.model_name
-      klass = "Post".dup
+      klass = +"Post"
       def klass.name; self end
 
       ActiveModel::Name.new(klass)

actionpack/test/dispatch/static_test.rb

@@ -31,15 +31,15 @@ def test_handles_urls_with_bad_encoding
   end
 
   def test_handles_urls_with_ascii_8bit
-    assert_equal "Hello, World!", get("/doorkeeper%E3E4".dup.force_encoding("ASCII-8BIT")).body
+    assert_equal "Hello, World!", get((+"/doorkeeper%E3E4").force_encoding("ASCII-8BIT")).body
   end
 
   def test_handles_urls_with_ascii_8bit_on_win_31j
     silence_warnings do
       Encoding.default_internal = "Windows-31J"
       Encoding.default_external = "Windows-31J"
     end
-    assert_equal "Hello, World!", get("/doorkeeper%E3E4".dup.force_encoding("ASCII-8BIT")).body
+    assert_equal "Hello, World!", get((+"/doorkeeper%E3E4").force_encoding("ASCII-8BIT")).body
   end
 
   def test_handles_urls_with_null_byte

actionpack/test/journey/router/utils_test.rb

@@ -23,7 +23,7 @@ def test_uri_unescape
         end
 
         def test_uri_unescape_with_utf8_string
-          assert_equal "Šašinková", Utils.unescape_uri("%C5%A0a%C5%A1inkov%C3%A1".dup.force_encoding(Encoding::US_ASCII))
+          assert_equal "Šašinková", Utils.unescape_uri((+"%C5%A0a%C5%A1inkov%C3%A1").force_encoding(Encoding::US_ASCII))
         end
 
         def test_normalize_path_not_greedy

actionview/lib/action_view/helpers/date_helper.rb

@@ -1053,7 +1053,7 @@ def build_select(type, select_options_as_html)
           select_options[:disabled] = "disabled" if @options[:disabled]
           select_options[:class] = css_class_attribute(type, select_options[:class], @options[:with_css_classes]) if @options[:with_css_classes]
 
-          select_html = "\n".dup
+          select_html = +"\n"
           select_html << content_tag("option".freeze, "", value: "") + "\n" if @options[:include_blank]
           select_html << prompt_option_tag(type, @options[:prompt]) + "\n" if @options[:prompt]
           select_html << select_options_as_html
@@ -1135,7 +1135,7 @@ def input_id_from_type(type)
         # Given an ordering of datetime components, create the selection HTML
         # and join them with their appropriate separators.
         def build_selects_from_types(order)
-          select = "".dup
+          select = +""
           first_visible = order.find { |type| !@options[:"discard_#{type}"] }
           order.reverse_each do |type|
             separator = separator(type) unless type == first_visible # don't add before first visible field

actionview/lib/action_view/helpers/javascript_helper.rb

@@ -15,8 +15,8 @@ module JavaScriptHelper
         "'"     => "\\'"
       }
 
-      JS_ESCAPE_MAP["\342\200\250".dup.force_encoding(Encoding::UTF_8).encode!] = "
"
-      JS_ESCAPE_MAP["\342\200\251".dup.force_encoding(Encoding::UTF_8).encode!] = "
"
+      JS_ESCAPE_MAP[(+"\342\200\250").force_encoding(Encoding::UTF_8).encode!] = "
"
+      JS_ESCAPE_MAP[(+"\342\200\251").force_encoding(Encoding::UTF_8).encode!] = "
"
 
       # Escapes carriage returns and single and double quotes for JavaScript segments.
       #

actionview/lib/action_view/helpers/tag_helper.rb

@@ -58,7 +58,7 @@ def content_tag_string(name, content, options, escape = true)
 
         def tag_options(options, escape = true)
           return if options.blank?
-          output = "".dup
+          output = +""
           sep    = " "
           options.each_pair do |key, value|
             if TAG_PREFIXES.include?(key) && value.is_a?(Hash)

actionview/lib/action_view/helpers/translation_helper.rb

@@ -98,7 +98,7 @@ def translate(key, options = {})
           raise e if raise_error
 
           keys = I18n.normalize_keys(e.locale, e.key, e.options[:scope])
-          title = "translation missing: #{keys.join('.')}".dup
+          title = +"translation missing: #{keys.join('.')}"
 
           interpolations = options.except(:default, :scope)
           if interpolations.any?

actionview/lib/action_view/log_subscriber.rb

@@ -16,15 +16,15 @@ def initialize
 
     def render_template(event)
       info do
-        message = "  Rendered #{from_rails_root(event.payload[:identifier])}".dup
+        message = +"  Rendered #{from_rails_root(event.payload[:identifier])}"
         message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
         message << " (#{event.duration.round(1)}ms)"
       end
     end
 
     def render_partial(event)
       info do
-        message = "  Rendered #{from_rails_root(event.payload[:identifier])}".dup
+        message = +"  Rendered #{from_rails_root(event.payload[:identifier])}"
         message << " within #{from_rails_root(event.payload[:layout])}" if event.payload[:layout]
         message << " (#{event.duration.round(1)}ms)"
         message << " #{cache_message(event.payload)}" unless event.payload[:cache_hit].nil?
@@ -85,7 +85,7 @@ def cache_message(payload) # :doc:
 
     def log_rendering_start(payload)
       info do
-        message = "  Rendering #{from_rails_root(payload[:identifier])}".dup
+        message = +"  Rendering #{from_rails_root(payload[:identifier])}"
         message << " within #{from_rails_root(payload[:layout])}" if payload[:layout]
         message
       end

actionview/lib/action_view/renderer/streaming_template_renderer.rb

@@ -33,7 +33,7 @@ def log_error(exception)
           logger = ActionView::Base.logger
           return unless logger
 
-          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  ")
           logger.fatal("#{message}\n\n")

actionview/lib/action_view/template.rb

@@ -286,7 +286,7 @@ def compile(mod)
 
         # Make sure that the resulting String to be eval'd is in the
         # encoding of the code
-        source = <<-end_src.dup
+        source = +<<-end_src
           def #{method_name}(local_assigns, output_buffer)
             _old_virtual_path, @virtual_path = @virtual_path, #{@virtual_path.inspect};_old_output_buffer = @output_buffer;#{locals_code};#{code}
           ensure
@@ -335,12 +335,12 @@ def locals_code
         locals = locals.grep(/\A@?(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/)
 
         # Assign for the same variable is to suppress unused variable warning
-        locals.each_with_object("".dup) { |key, code| code << "#{key} = local_assigns[:#{key}]; #{key} = #{key};" }
+        locals.each_with_object(+"") { |key, code| code << "#{key} = local_assigns[:#{key}]; #{key} = #{key};" }
       end
 
       def method_name
         @method_name ||= begin
-          m = "_#{identifier_method_name}__#{@identifier.hash}_#{__id__}".dup
+          m = +"_#{identifier_method_name}__#{@identifier.hash}_#{__id__}"
           m.tr!("-".freeze, "_".freeze)
           m
         end

actionview/lib/action_view/template/resolver.rb

@@ -16,7 +16,7 @@ class Path
       alias_method :partial?, :partial
 
       def self.build(name, prefix, partial)
-        virtual = "".dup
+        virtual = +""
         virtual << "#{prefix}/" unless prefix.empty?
         virtual << (partial ? "_#{name}" : name)
         new name, prefix, partial, virtual