Add frozen_string_literal: true in order to suppress 'warning: literal string will be frozen in the future'

lib/fluent/command/ctl.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -67,7 +69,7 @@ def initialize(argv = ARGV)
     end
 
     def help_text
-      text = "\n"
+      text = +"\n"
       if Fluent.windows?
         text << "Usage: #{$PROGRAM_NAME} COMMAND [PID_OR_SVCNAME]\n"
       else

lib/fluent/command/plugin_config_formatter.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -79,7 +81,7 @@ def call
   private
 
   def dump_txt(dumped_config)
-    dumped = ""
+    dumped = +""
     plugin_helpers = dumped_config.delete(:plugin_helpers)
     if plugin_helpers && !plugin_helpers.empty?
       dumped << "helpers: #{plugin_helpers.join(',')}\n"
@@ -101,7 +103,7 @@ def dump_txt(dumped_config)
   end
 
   def dump_section_txt(base_section, level = 0)
-    dumped = ""
+    dumped = +""
     indent = " " * level
     if base_section[:section]
       sections = []
@@ -135,10 +137,10 @@ def dump_section_txt(base_section, level = 0)
   end
 
   def dump_markdown(dumped_config)
-    dumped = ""
+    dumped = +""
     plugin_helpers = dumped_config.delete(:plugin_helpers)
     if plugin_helpers && !plugin_helpers.empty?
-      dumped = "## Plugin helpers\n\n"
+      dumped = +"## Plugin helpers\n\n"
       plugin_helpers.each do |plugin_helper|
         dumped << "* #{plugin_helper_markdown_link(plugin_helper)}\n"
       end
@@ -156,7 +158,7 @@ def dump_markdown(dumped_config)
   end
 
   def dump_section_markdown(base_section, level = 0)
-    dumped = ""
+    dumped = +""
     if base_section[:section]
       sections = []
       params = base_section

lib/fluent/compat/formatter_utils.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #

lib/fluent/compat/output.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #

lib/fluent/compat/record_filter_mixin.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -21,7 +23,7 @@ def filter_record(tag, time, record)
       end
 
       def format_stream(tag, es)
-        out = ''
+        out = +''
         es.each {|time,record|
           tag_temp = tag.dup
           filter_record(tag_temp, time, record)

lib/fluent/config/element.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -141,7 +143,7 @@ def check_not_fetched(&block)
       def to_s(nest = 0)
         indent = "  " * nest
         nindent = "  " * (nest + 1)
-        out = ""
+        out = +""
         if @arg.nil? || @arg.empty?
           out << "#{indent}<#{@name}>\n"
         else
@@ -230,7 +232,7 @@ def dump_value(k, v, nindent)
       end
 
       def self.unescape_parameter(v)
-        result = ''
+        result = +''
         v.each_char { |c| result << LiteralParser.unescape_char(c) }
         result
       end

lib/fluent/config/literal_parser.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -228,8 +230,8 @@ def scan_json(is_array)
         # Yajl does not raise ParseError for incomplete json string, like '[1', '{"h"', '{"h":' or '{"h1":1'
         # This is the reason to use JSON module.
 
-        buffer = (is_array ? "[" : "{")
-        line_buffer = ""
+        buffer = +(is_array ? "[" : "{")
+        line_buffer = +""
 
         until result
           char = getch
@@ -252,7 +254,7 @@ def scan_json(is_array)
                 # ignore comment char
               end
               buffer << line_buffer + "\n"
-              line_buffer = ""
+              line_buffer = +""
             else
               # '#' is a char in json string
               line_buffer << char
@@ -263,7 +265,7 @@ def scan_json(is_array)
 
           if char == "\n"
             buffer << line_buffer + "\n"
-            line_buffer = ""
+            line_buffer = +""
             next
           end
 

lib/fluent/config/types.rb

@@ -183,7 +183,7 @@ def self.enum_value(val, opts = {}, name = nil)
         value
       else
         case type
-        when :string  then value.to_s.force_encoding(Encoding::UTF_8)
+        when :string  then (+(value.to_s)).force_encoding(Encoding::UTF_8)
         when :integer then INTEGER_TYPE.call(value, opts, name)
         when :float   then FLOAT_TYPE.call(value, opts, name)
         when :size then Config.size_value(value, opts, name)

lib/fluent/config/yaml_parser/fluent_value.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -30,7 +32,7 @@ def to_element
 
         StringValue = Struct.new(:val, :context) do
           def to_s
-            context.instance_eval("\"#{val}\"")
+            context.instance_eval("\"#{val}\"").freeze
           rescue Fluent::SetNil => _
             ''
           rescue Fluent::SetDefault => _

lib/fluent/log.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -205,7 +207,7 @@ def format=(fmt)
         @format = :text
         @formatter = Proc.new { |type, time, level, msg|
           r = caller_line(type, time, @depth_offset, level)
-          r << msg
+          r += msg
           r
         }
       when :json
@@ -550,7 +552,7 @@ def get_worker_id(type)
 
     def event(level, args)
       time = Time.now
-      message = @optional_header ? @optional_header.dup : ''
+      message = @optional_header ? @optional_header.dup : +''
       map = @optional_attrs ? @optional_attrs.dup : {}
       args.each {|a|
         if a.is_a?(Hash)
@@ -563,7 +565,7 @@ def event(level, args)
       }
 
       map.each_pair {|k,v|
-        if k == "error".freeze && v.is_a?(Exception) && !map.has_key?("error_class")
+        if k == "error" && v.is_a?(Exception) && !map.has_key?("error_class")
           message << " error_class=#{v.class.to_s} error=#{v.to_s.inspect}"
         else
           message << " #{k}=#{v.inspect}"
@@ -598,7 +600,7 @@ def caller_line(type, time, depth, level)
       worker_id_part = if type == :default && (@process_type == :worker0 || @process_type == :workers)
                          @worker_id_part
                        else
-                         "".freeze
+                         ""
                        end
       log_msg = "#{format_time(time)} [#{LEVEL_TEXT[level]}]: #{worker_id_part}"
       if @debug_mode

lib/fluent/match.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -43,7 +45,7 @@ def initialize(pat)
       end
 
       stack = []
-      regex = ['']
+      regex = [+'']
       escape = false
       dot = false
 
@@ -105,15 +107,15 @@ def initialize(pat)
         elsif c == "{"
           # or
           stack.push []
-          regex.push ''
+          regex.push(+'')
 
         elsif c == "}" && !stack.empty?
           stack.last << regex.pop
           regex.last << Regexp.union(*stack.pop.map {|r| Regexp.new(r) }).to_s
 
         elsif c == "," && !stack.empty?
           stack.last << regex.pop
-          regex.push ''
+          regex.push(+'')
 
         elsif /[a-zA-Z0-9_]/.match?(c)
           regex.last << c

lib/fluent/plugin/buffer/file_chunk.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -24,7 +26,7 @@ class Buffer
       class FileChunk < Chunk
         class FileChunkError < StandardError; end
 
-        BUFFER_HEADER = "\xc1\x00".force_encoding(Encoding::ASCII_8BIT).freeze
+        BUFFER_HEADER = (+"\xc1\x00").force_encoding(Encoding::ASCII_8BIT).freeze
 
         ### buffer path user specified : /path/to/directory/user_specified_prefix.*.log
         ### buffer chunk path          : /path/to/directory/user_specified_prefix.b513b61c9791029c2513b61c9791029c2.log

lib/fluent/plugin/buffer/memory_chunk.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -22,7 +24,7 @@ class Buffer
       class MemoryChunk < Chunk
         def initialize(metadata, compress: :text)
           super
-          @chunk = ''.force_encoding(Encoding::ASCII_8BIT)
+          @chunk = (+'').force_encoding(Encoding::ASCII_8BIT)
           @chunk_bytes = 0
           @adding_bytes = 0
           @adding_size = 0
@@ -68,7 +70,7 @@ def empty?
 
         def purge
           super
-          @chunk = ''.force_encoding("ASCII-8BIT")
+          @chunk = (+'').force_encoding("ASCII-8BIT")
           @chunk_bytes = @size = @adding_bytes = @adding_size = 0
           true
         end

lib/fluent/plugin/compressable.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -57,7 +59,7 @@ def decompress(compressed_data = nil, output_io: nil, input_io: nil)
       def string_decompress(compressed_data)
         io = StringIO.new(compressed_data)
 
-        out = ''
+        out = +''
         loop do
           gz = Zlib::GzipReader.new(io)
           out << gz.read

lib/fluent/plugin/formatter_csv.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -27,7 +29,7 @@ class CsvFormatter < Formatter
       helpers :record_accessor
 
       config_param :delimiter, default: ',' do |val|
-        ['\t', 'TAB'].include?(val) ? "\t".freeze : val.freeze
+        ['\t', 'TAB'].include?(val) ? "\t" : val.freeze
       end
       config_param :force_quotes, :bool, default: true
       # "array" looks good for type of :fields, but this implementation removes tailing comma
@@ -50,13 +52,13 @@ def configure(conf)
         end
 
         @generate_opts = {col_sep: @delimiter, force_quotes: @force_quotes, headers: @fields,
-                          row_sep: @add_newline ? :auto : "".force_encoding(Encoding::ASCII_8BIT)}
+                          row_sep: @add_newline ? :auto : (+"").force_encoding(Encoding::ASCII_8BIT)}
         # Cache CSV object per thread to avoid internal state sharing
         @cache = {}
       end
 
       def format(tag, time, record)
-        csv = (@cache[Thread.current] ||= CSV.new("".force_encoding(Encoding::ASCII_8BIT), **@generate_opts))
+        csv = (@cache[Thread.current] ||= CSV.new((+"").force_encoding(Encoding::ASCII_8BIT), **@generate_opts))
         line = (csv << record).string.dup
         # Need manual cleanup because CSV writer doesn't provide such method.
         csv.rewind
@@ -65,7 +67,7 @@ def format(tag, time, record)
       end
 
       def format_with_nested_fields(tag, time, record)
-        csv = (@cache[Thread.current] ||= CSV.new("".force_encoding(Encoding::ASCII_8BIT), **@generate_opts))
+        csv = (@cache[Thread.current] ||= CSV.new((+"").force_encoding(Encoding::ASCII_8BIT), **@generate_opts))
         values = @accessors.map { |a| a.call(record) }
         line = (csv << values).string.dup
         # Need manual cleanup because CSV writer doesn't provide such method.

lib/fluent/plugin/formatter_json.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #

lib/fluent/plugin/formatter_ltsv.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -25,13 +27,13 @@ class LabeledTSVFormatter < Formatter
 
       # http://ltsv.org/
 
-      config_param :delimiter, :string, default: "\t".freeze
-      config_param :label_delimiter, :string, default: ":".freeze
-      config_param :replacement, :string, default: " ".freeze
+      config_param :delimiter, :string, default: "\t"
+      config_param :label_delimiter, :string, default: ":"
+      config_param :replacement, :string, default: " "
       config_param :add_newline, :bool, default: true
 
       def format(tag, time, record)
-        formatted = ""
+        formatted = +""
         record.each do |label, value|
           formatted << @delimiter if formatted.length.nonzero?
           formatted << "#{label}#{@label_delimiter}#{value.to_s.gsub(@delimiter, @replacement)}"

lib/fluent/plugin/formatter_out_file.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 #
 # Fluentd
 #
@@ -29,9 +31,9 @@ class OutFileFormatter < Formatter
       config_param :output_tag, :bool, default: true
       config_param :delimiter, default: "\t" do |val|
         case val
-        when /SPACE/i then ' '.freeze
-        when /COMMA/i then ','.freeze
-        else "\t".freeze
+        when /SPACE/i then ' '
+        when /COMMA/i then ','
+        else "\t"
         end
       end
       config_set_default :time_type, :string
@@ -43,7 +45,7 @@ def configure(conf)
       end
 
       def format(tag, time, record)
-        header = ''
+        header = +''
         header << "#{@timef.format(time)}#{@delimiter}" if @output_time
         header << "#{tag}#{@delimiter}" if @output_tag
         "#{header}#{Yajl.dump(record)}#{@newline}"