Forum: Ruby-core [Bug #1689] ARGF.binmode Affects Encoding Inconsistently

Bug #1689: ARGF.binmode Affects Encoding Inconsistently
http://redmine.ruby-lang.org/issues/show/1689

Author: Run Paint Run Run
Status: Open, Priority: Low
Category: M17N
ruby -v: ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]

The IO#binmode documentation promises that "content is treated as 
ASCII-8BIT". I assumed this would apply to ARGF, too. It sometimes does:

    $ echo "a" | ruby -ve 'ARGF.binmode; p ARGF.readpartial(1).encoding'
    ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]
    #<Encoding:ASCII-8BIT>

But often doesn't:

    $ echo "a" | ruby -ve 'ARGF.binmode; p ARGF.read.encoding'
    ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]
    #<Encoding:UTF-8>

    $ echo "a" | ruby -ve 'ARGF.binmode; p ARGF.getc.encoding'
    ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]
    #<Encoding:UTF-8>

    $ echo "a" | ruby -ve 'ARGF.binmode; p ARGF.readchar.encoding'
    ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]
    #<Encoding:UTF-8>

    $ ruby -ve 'ARGF.binmode; p ARGF.read.encoding' /usr/bin/ruby
    ruby 1.9.2dev (2009-06-21 trunk 23774) [i686-linux]
    #<Encoding:UTF-8>

I had assumed that ARGF.binmode would set the encoding of all files read 
in to ASCII-8BIT. This is how, for instance, File works: File.binmode 
sets the output of File.read to ASCII-8BIT, even when the contents is 
entirely ASCII. Setting the default external encoding to ASCII-8BIT 
fixes these cases.

So. given that I'm trying to document ARGF, my questions are:

1) Why the inconsistency between ARGF.readpartial and the rest of the 
ARGF methods?
2) Should the default external encoding take precedence over 'binmode'?

Issue #1689 has been updated by Yukihiro Matsumoto.

Status changed from Open to Closed
% Done changed from 0 to 100

Applied in changeset r23853.
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http://redmine.ruby-lang.org/issues/show/1689