From: "Tietew (Toru Iwase)" <tietew@...>
Date: 2013-02-25T18:03:27+09:00
Subject: [ruby-dev:47108] [ruby-trunk - Bug #7954][Open] "あ".byteslice(0,2).valid_encoding? should return false


Issue #7954 has been reported by Tietew (Toru Iwase).

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Bug #7954: "あ".byteslice(0,2).valid_encoding? should return false
https://bugs.ruby-lang.org/issues/7954

Author: Tietew (Toru Iwase)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 2.0.0
ruby -v: 2.0.0p0


=begin
valid encodingな文字列に対するString#bytesliceがinvalid encodingなバイト列を生成してもvalid_encoding?がtrueになります。
これはfalseになるべきだと思います。

なお、1.9.3も同じ挙動です。

 irb(main):001:0> RUBY_DESCRIPTION
 => "ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux]"
 irb(main):002:0> "あ".encoding
 => #<Encoding:UTF-8>
 irb(main):003:0> "あ".valid_encoding?
 => true
 irb(main):004:0> "あ".byteslice(0,2)
 => "\xE3\x81"
 irb(main):005:0> "あ".byteslice(0,2).valid_encoding?
 => true
 irb(main):006:0> "\xE3\x81".encoding
 => #<Encoding:UTF-8>
 irb(main):007:0> "\xE3\x81".valid_encoding?
 => false

ちなみに、invalidな文字列を正しい位置でbytesliceすると正しくvalidと判定されます。

 irb(main):025:0> "あ\xE3".valid_encoding?
 => false
 irb(main):026:0> "あ\xE3".byteslice(0,3).valid_encoding?
 => true
=end


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