[GHC] #4215: canonicalizePath behaves strangely with paths that do not exist

[GHC]

#4215: canonicalizePath behaves strangely with paths that do not exist
---------------------------------+------------------------------------------
    Reporter:  creswick          |       Owner:                             
        Type:  bug               |      Status:  new                        
    Priority:  normal            |   Component:  libraries/directory        
     Version:  6.12.3            |    Keywords:                             
          Os:  Unknown/Multiple  |    Testcase:                             
Architecture:  Unknown/Multiple  |     Failure:  Incorrect result at runtime
---------------------------------+------------------------------------------
 The behavior of System.Directory.canonicalizePath is not documented (and
 perhaps not defined) for paths that do not exist on the file system.  The
 documentation should, minimally, indicate that this is the case.  Ideally,
 the behavior would be well-defined.

 This is complicated by differing behaviors of the underlying
 realpath(char*, char*) function in Linux and OS X.  On Linux, realpath
 changes its behavior if the last existing portion of the input path is a
 file vs. a directory, while OS X does not alter behavior in these two
 cases.  Specifically, assume the following:

  * $HOME/tmp/foo is a file.
  * $HOME/tmp/bar is a directory.
  * $HOME/tmp/baz does not exist.

 Linux:
 {{{
 Prelude System.Directory> canonicalizePath "/home/creswick/tmp/foo/subdir"
 "/home/creswick/tmp/foo"
 Prelude System.Directory> canonicalizePath "/home/creswick/tmp/bar/subdir"
 "/home/creswick/tmp/bar/subdir"
 Prelude System.Directory> canonicalizePath "/home/creswick/tmp/baz/subdir"
 "/home/creswick/tmp/baz"
 }}}

 OS-X:
 {{{
 Prelude System.Directory> canonicalizePath "/Users/hudson/tmp/foo/subdir"
 "/Users/hudson/tmp/foo/subdir"
 Prelude System.Directory> canonicalizePath "/Users/hudson/tmp/bar/subdir"
 "/Users/hudson/tmp/bar/subdir"
 Prelude System.Directory> canonicalizePath "/Users/hudson/tmp/baz/subdir"
 "/Users/hudson/tmp/baz"
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4215>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler