(PUP-11841) Create mutable strings

In preparation for moving to frozen/immutable strings, explicitly create mutable
strings in cases where we create a string buffer and append to it. There are
multiple ways of creating a mutual string:

    ''.dup
    -''
    String.new

Although the latter is more verbose, I think it's better to be explicit.

Author: joshcooper

lib/puppet/application/doc.rb

@@ -151,7 +151,7 @@ def rdoc
   end
 
   def other
-    text = ""
+    text = String.new
     with_contents = options[:references].length <= 1
     exit_code = 0
     require_relative '../../puppet/util/reference'

lib/puppet/face/config.rb

@@ -81,7 +81,7 @@
     end
 
     when_rendering :console do |to_be_rendered|
-      output = ''
+      output = String.new
       if to_be_rendered.keys.length > 1
         to_be_rendered.keys.sort.each do |setting|
           output << "#{setting} = #{to_be_rendered[setting]}\n"

lib/puppet/face/epp.rb

@@ -366,7 +366,7 @@
   end
 
   def dump_parse(source, filename, options, show_filename = true)
-    output = ""
+    output = String.new
     evaluating_parser = Puppet::Pops::Parser::EvaluatingParser::EvaluatingEppParser.new
     begin
       if options[:validate]
@@ -450,7 +450,7 @@ def render_inline(epp_source, compiler, options)
 
   def render_file(epp_template_name, compiler, options, show_filename, file_nbr)
     template_args = get_values(compiler, options)
-    output = ""
+    output = String.new
     begin
       if show_filename && options[:header]
         output << "\n" unless file_nbr == 1

lib/puppet/face/module/list.rb

@@ -73,7 +73,7 @@
       environment     = result[:environment]
       modules_by_path = result[:modules_by_path]
 
-      output = ''
+      output = String.new
 
       warn_unmet_dependencies(environment)
 
@@ -247,7 +247,7 @@ def list_build_tree(list, ancestors=[], parent=nil, params={})
   # Returns a Hash
   #
   def list_build_node(mod, parent, params)
-    str = ''
+    str = String.new
     str << (mod.forge_name ? mod.forge_name.tr('/', '-') : mod.name)
     str << ' (' + colorize(:cyan, mod.version ? "v#{mod.version}" : '???') + ')'
 

lib/puppet/face/parser.rb

@@ -173,7 +173,7 @@
   end
 
   def dump_parse(source, filename, options, show_filename = true)
-    output = ""
+    output = String.new
     evaluating_parser = Puppet::Pops::Parser::EvaluatingParser.new
     begin
       if options[:validate]

lib/puppet/ffi/windows/api_types.rb

@@ -20,7 +20,7 @@ def attach_function_private(*args)
 
     class ::FFI::Pointer
       NULL_HANDLE = 0
-      WCHAR_NULL = "\0\0".force_encoding('UTF-16LE').freeze
+      WCHAR_NULL = String.new("\0\0").force_encoding('UTF-16LE').freeze
 
       def self.from_string_to_wide_string(str, &block)
         str = Puppet::Util::Windows::String.wide_string(str)

lib/puppet/file_system/posix.rb

@@ -12,8 +12,8 @@ def binread(path)
   def compare_stream(path, stream)
     open(path, 0, 'rb') do |this|
       bsize = stream_blksize(this, stream)
-      sa = "".force_encoding('ASCII-8BIT')
-      sb = "".force_encoding('ASCII-8BIT')
+      sa = String.new.force_encoding('ASCII-8BIT')
+      sb = String.new.force_encoding('ASCII-8BIT')
       loop do
         this.read(bsize, sa)
         stream.read(bsize, sb)

lib/puppet/indirector/file_bucket_file/file.rb

@@ -57,7 +57,7 @@ def list(request)
       end
       # Setting hash's default value to [], needed by the following loop
       bucket = Hash.new {[]}
-      msg = ""
+      msg = String.new
       # Get all files with mtime between 'from' and 'to'
       Pathname.new(request.options[:bucket_path]).find { |item|
         if item.file? and item.basename.to_s == "paths"

lib/puppet/indirector/indirection.rb

@@ -80,7 +80,7 @@ def expiration
 
   # Generate the full doc string.
   def doc
-    text = ""
+    text = String.new
 
     text << scrub(@doc) << "\n\n" if @doc
 

lib/puppet/module_tool.rb

@@ -69,7 +69,7 @@ def self.is_module_root?(path)
     # Builds a formatted tree from a list of node hashes containing +:text+
     # and +:dependencies+ keys.
     def self.format_tree(nodes, level = 0)
-      str = ''
+      str = String.new
       nodes.each_with_index do |node, i|
         last_node = nodes.length - 1 == i
         deps = node[:dependencies] || []