[ruby-core:46805] [ruby-trunk - Bug #6608] File.join behavior

Issue #6608 has been updated by Eregon (Benoit Daloze).


=begin
Thank you for the detailed explanation.

I see your point and the spec seems clear, I'll update RubySpec with this.

Indeed, the documentation of Dir.glob mentions:

     \ :
      Escapes the next metacharacter. Note that this means you cannot use
      backslash in windows as part of a glob, i.e. Dir["c:\foo*"] will not work
      use Dir["c:/foo*"] instead
=end

----------------------------------------
Bug #6608: File.join behavior
https://bugs.ruby-lang.org/issues/6608#change-28479

Author: Eregon (Benoit Daloze)
Status: Rejected
Priority: Normal
Assignee: usa (Usaku NAKAMURA)
Category: 
Target version: 
ruby -v: ruby 1.9.2p290 (2011-07-09) [i386-mingw32]


Hello,

I would like to know if the current behavior of File.join is intended, and what should be its specification, especially on systems with File::ALT_SEPARATOR.

File.join adds '/' for joining if no separator is present:
File.join('a', 'b') # => "a/b"
And if a forward slash is present or two, it just acts the same:
File.join('a', '/b') or File.join('a/', 'b') # => "a/b" # => "a/b"

(These are expected)

But when a backward slash is present (= File::ALT_SEPARATOR), it seems it is kept only if it is on the right side or no other separator is present:
File.join('a', '\b') or File.join('a\\', 'b') # => "a\\b"
File.join('a/', '\b') # => "a\\b"
but
File.join('a\\', '/b') # => "a/b"

And it seems the right part is never touched, while the left part loses all its separators, unless there are none on the right side.
File.join('a/\/', '\b') # => "a\\b"
File.join('a/\/', '\//b') # => "a\\//b"
File.join('a/\/', 'b') # => "a/\/b"

Ruby is usually giving only forward-slash paths (Dir.getwd) and accepts them only in some cases (Dir.glob).
I think conceptually File.join should remove all "\" and replace them by "/", like File.expand_path does for example.
I guess this is not done for efficiency reasons.
But it also means it might produce not natural behavior:
Dir.glob(File.join('C:', '\WINDOWS', '*')) == Dir.glob('C:\WINDOWS/*') # =>  ["C:WINDOWS/system"] # sounds like a bug, isn't it?
but
Dir.glob(File.join('C:', '/WINDOWS', '*')) # => all files/dirs under C:/WINDOWS

The current RubySpec is a bit misleading in this regard: https://github.com/rubyspec/rubyspec/blob/master/core/file/join_spec.rb#L21-26


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