From: "duerst (Martin Dürst)" <duerst@...>
Date: 2012-11-08T12:51:52+09:00
Subject: [ruby-core:49081] [ruby-trunk - Bug #7200] Setting external encoding with BOM|


Issue #7200 has been updated by duerst (Martin D��rst).


Brian (or others),

[written in part to help Shouhei a bit]

Do you have an actual use case where you need something like
   f.set_encoding "bom|utf-16be", "euc-jp"
If yes, can you explain?

The current behavior in in part influenced by implementation. But there is also a conceptual issue, because "bom|" only applies at the start of the file, and may have different implications for input (check for a BOM) and output (add a BOM). So we have to carefully think what's the best way to make this easy for programmers to use the right way.

Regards,    Martin.
----------------------------------------
Bug #7200: Setting external encoding with BOM|
https://bugs.ruby-lang.org/issues/7200#change-32609

Author: brixen (Brian Ford)
Status: Assigned
Priority: Normal
Assignee: naruse (Yui NARUSE)
Category: 
Target version: 2.0.0
ruby -v: ruby 1.9.3p286 (2012-10-12 revision 37165) [x86_64-darwin10.8.0]


File.open will accept, for example, :encoding => "bom|utf-16be:euc-jp" or :encoding => "bom|utf-16be". However, :external_encoding => "bom|utf-16be" raises an ArgumentError. Likewise, IO#set_encoding will accept "bom|utf-16be:euc-jp" but raises an ArgumentError if passed "bom|utf-16be", "euc-jp".

It is inconsistent to accept "bom|utf-*" in some cases and not others.

See the following IRB transcript.

$ irb
1.9.3p286 :001 > f = File.open "foo.txt", "r", :encoding => "bom|utf-16be:euc-jp"
 => #<File:foo.txt> 
1.9.3p286 :002 > f.internal_encoding
 => #<Encoding:EUC-JP> 
1.9.3p286 :003 > f.external_encoding
 => #<Encoding:UTF-16BE> 
1.9.3p286 :004 > f.close
 => nil 
1.9.3p286 :005 > f = File.open "foo.txt", "r"
 => #<File:foo.txt> 
1.9.3p286 :006 > f.set_encoding "bom|utf-16be:euc-jp"
 => #<File:foo.txt> 
1.9.3p286 :007 > f.internal_encoding
 => #<Encoding:EUC-JP> 
1.9.3p286 :008 > f.external_encoding
 => #<Encoding:UTF-16BE> 
1.9.3p286 :009 > f.close
 => nil 
1.9.3p286 :010 > f = File.open "foo.txt", "r"
 => #<File:foo.txt> 
1.9.3p286 :011 > f.set_encoding "bom|utf-16be", "euc-jp"
ArgumentError: unknown encoding name - bom|utf-16be
	from (irb):11:in `set_encoding'
	from (irb):11
	from /Users/brian/.rvm/rubies/ruby-1.9.3-p286/bin/irb:16:in `<main>'
1.9.3p286 :012 > f = File.open "foo.txt", "w", :external_encoding => "bom|utf-16be"
ArgumentError: unknown encoding name - bom|utf-16be
	from (irb):12:in `initialize'
	from (irb):12:in `open'
	from (irb):12
	from /Users/brian/.rvm/rubies/ruby-1.9.3-p286/bin/irb:16:in `<main>'
1.9.3p286 :013 > f = File.open "foo.txt", "rb", :encoding => "bom|utf-16be"
 => #<File:foo.txt> 

Thanks,
Brian


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