What is the rationale behind std.file.setAttributes ?

[Marco Leise]

Am Sat, 28 Dec 2013 05:13:57 +0100
schrieb Martin Nowak <code at dawg.eu>:

> On 12/28/2013 05:01 AM, Marco Leise wrote:
> > Ok, so there is a compatibility field for the file attributes
> > in a .zip file. So a .zip extractor has to version(Windows/Posix)
> > anyway to check if the attributes for a given file are
> > compatible with the host OS. Couldn't SetFileAttributes and
> > chmod be called right there on the spot?
> 
> It does in memory extraction, you have to set the attributes after 
> writing out the file.
> https://github.com/D-Programming-Language/installer/pull/31
> https://d.puremagic.com/issues/show_bug.cgi?id=11789
> https://github.com/D-Programming-Language/installer/pull/33

Some backlog! So getAttributes was there already, the dmd
installer script used a custom "setAttributes" to extract ZIP
files, and so it was decided that setAttributes should be in
Phobos, too. (in short)

Don't kill me, but I think this version of setAttributes should
stay local to create_dmd_release (or std.zip if it was
extended to support extraction to the file system). In the
most general use case it still requires a code block like this:

  bool useFileAttr = false;
  version (Posix) {
      useFileAttr = data.isMeantForPosix;
  } else version (Windows) {
      useFileAttr = data.isMeantForWindows;
  }

  if (useFileAttr)
      std.file.setAttributes(data.fileName, data.fileAttribs);

Meaning it is (as far as I can see) only of use for external
data blocks that contain OS specific file attributes in a shared
32-bit field and at that point it doesn't gain much over:

  version (Posix) {
      if (data.isMeantForPosix)
          chmod( toUTFz!(char*)(data.fileName), data.fileAttr );
  } else version (Windows) {
      if (data.isMeantForWindows)
          SetFileAttributesW( toUTFz!(wchar*)(data.fileName), data.fileAttr );
  }

For Phobos we need portable solutions. But it is also clear that
std.file.setAttributes cannot be replaced to 100% by a portable
solution. The question is: Does portable code _care_ about setting
each possible chmod flag or Windows file attribute? Or are the use
cases much more limited there, like making a file read-only or
querying if it is a directory?

-- 
Marco