Re: [PATCH] run-command: don't try to execute directories

[Jeff King <peff@peff.net>]

On Tue, Oct 02, 2012 at 09:32:11PM +0200, Carlos Martín Nieto wrote:

> >> @@ -101,8 +102,9 @@ static char *locate_in_PATH(const char *file)
> >>  		}
> >>  		strbuf_addstr(&buf, file);
> >>  
> >> -		if (!access(buf.buf, F_OK))
> >> +		if (!stat(buf.buf, &st) && !S_ISDIR(st.st_mode)) {
> >>  			return strbuf_detach(&buf, NULL);
> >> +		}
> >
> > So we used to say "if it exists and accessible, return that".  Now
> > we say "if it exists and is not a directory, return that".
> >
> > I have to wonder what would happen if it exists as a non-directory
> > but we cannot access it.  Is that a regression?
> 
> I guess it would be, yeah. Would this be related to tha situation where
> the user isn't allowed to access something in their PATH?

This code path is related to correcting EACCES errors into ENOENT. But
it does not bother checking permissions itself.  We know there is some
permission problem, because execvp told us EACCES, so we are only
checking whether such a file actually exists at all in the PATH. And
that is why we are using F_OK with access, and not X_OK.

So any reason for which stat() would fail would presumably cause
access(F_OK) to fail, too (mostly things like leading directories not
being readable), and I think converting the access into a stat is OK.

Adding the !ISDIR on top of it makes sense if you want to consider the
directory in your PATH to be a harmless thing to be ignored. However, I
am not sure that is a good idea. The intent of ignoring the original
EACCES is that it could be caused by totally uninteresting crap, like an
inaccessible directory in your PATH.

Whereas in this case, the error really is that we found "git-foo", but
it is somehow broken. And it almost certainly is a configuration error
on the part of the user (why would they put a git-foo directory in their
PATH? Presumably they meant to put its contents into the PATH).

So I think your implementation is fine, but I'm a little dubious of the
value of ignoring such an error.

-Peff