Issue #7964 has been updated by naruse (Yui NARUSE).



The examples are not equal.
Correct comparison is

 StringIO.open a, "w" do |io|
   io.write(b)
 end
 
 File.open "data.txt", "w" do |io|
   io.write b
 end

So it won't raise error even if StringIO supports external/internal encoding.


duerst (Martin Dürst) wrote:
> nobu (Nobuyoshi Nakada) wrote:
> > Currently, StringIO does not support encoding conversion on write, so `io.write(b)' does not raise any exceptions.
> 
> Should StringIO support encoding conversion? I think it should, because it should work like IO. However, the question is whether the resulting string should always be BINARY (exactly mirroring what happens with real IO), or whether it should have its own encoding (this might allow collecting substrings in different encodings into a string with a single encoding without any explicit conversions).

Agreed.

> I think that somebody should open a feature for this, and of course patches would be welcome.
> 
> As an aside, I think it would be easier implementing StingIO in Ruby, or is StringIO performance critical?

see https://bugs.ruby-lang.org/issues/5677
----------------------------------------
Bug #7964: Writing an ASCII-8BIT String to a StringIO created from a UTF-8 String
https://bugs.ruby-lang.org/issues/7964#change-37096

Author: brixen (Brian Shirai)
Status: Assigned
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: ext
Target version: current: 2.1.0
ruby -v: ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-darwin10.8.0]


=begin
In the following script, an ASCII-8BIT String is written to a StringIO created with a UTF-8 String without error. However, a << b or a + b will raise an exception, as will writing an ASCII-8BIT String to a File with UTF-8 external encoding.

+ $ cat file_enc.rb
  # encoding: utf-8
  require 'stringio'

  a = "On a very cold morning, it was -8°F."
  b = a.dup.force_encoding "ascii-8bit"

  io = StringIO.new a
  io.write(b)
  p io.string.encoding

  File.open "data.txt", "w:utf-8" do |f|
    f.write a
    f.write b
  end

+ $ ruby2.0 -v file_enc.rb
  ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-darwin10.8.0]
  #<Encoding:UTF-8>
  file_enc.rb:13:in `write': "\xC2" from ASCII-8BIT to UTF-8 (Encoding::UndefinedConversionError)
  	from file_enc.rb:13:in `block in <main>'
  	from file_enc.rb:11:in `open'
  	from file_enc.rb:11:in `<main>'

+ $ ruby1.9.3 -v file_enc.rb
  ruby 1.9.3p327 (2012-11-10 revision 37606) [x86_64-darwin10.8.0]
  #<Encoding:UTF-8>
  file_enc.rb:13:in `write': "\xC2" from ASCII-8BIT to UTF-8 (Encoding::UndefinedConversionError)
  	from file_enc.rb:13:in `block in <main>'
  	from file_enc.rb:11:in `open'
  	from file_enc.rb:11:in `<main>'
=end



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