Re: Lua 5.2 beta: default module path incompatibility

[Dirk Laurie <dpl@...>]

On Thu, Sep 22, 2011 at 02:39:31AM +0200, David Manura wrote:
> On Tue, Sep 20, 2011 at 7:26 AM, liam mail <liam.list@googlemail.com> wrote:
> > On 20 September 2011 12:04, Dirk Laurie <dpl@sun.ac.za> wrote:
> >>  The default set in luaconf.h for both package.path and package.cpath
> >>  in Lua 5.2.0 beta puts the present working directory last, whereas in
> >>  Lua 5.1.4 it was put first.[...]
> >> It is difficult to understand why this change has been made.  It causes
> >> any application distributed with customized versions of packages that
> >> happen to installed system-wide to break unless the application explicitly
> >> sets the path.
> 
> Arguments for the new behavior were raised in [1,2].
> 
> Note that the path "./?.lua" is relative to the current directory, but
> you'd probably rather search relative to the Lua executable (i.e. "!"
> style LUA_PATH in Windows / LuaDist setprogdir [3]) or relative to the
> current script [4-8].  Perl's FindBin and "use lib" [9] do this well,
> and I've contemplated writing the analogue of both modules for Lua,
> and submitting it to distributions like LuaForWindows, because the
> need is so common.  IMO, "./?.lua" is a hack that introduces some
> modes of failure.
> 
> [1] http://lua-users.org/lists/lua-l/2009-07/msg00106.html
> [2] http://lua-users.org/lists/lua-l/2009-05/msg00559.html
> 

Maybe an even better solution would thus be to omit the current directory 
altogether from the default path.  It's easy enough to concatenate 
"./?.lua;" in front or ";./?.lua" at the back of package.path, and then
the code contains an explicit indication that one is doing so.

But '"./?.lua" is a hack' is too harsh.  It is a typical Lua compromise 
between security and ease of use, while still offering the user ways
to enhance either at the expense of the other.

Dirk