[Dev-luatex] Module searching

[Heiko Oberdiek]

On Mon, Dec 10, 2007 at 11:51:28PM +0100, Hans Hagen wrote:

> Heiko Oberdiek wrote:
> > Example: There is a package "foobar" with module "foobar.hello".

> > I haven't found a solution using kpse functions.
> >   kpsewhich --format=texmfscripts foobar/hello.lua
> > doesn't find the file.
> 
> well, maybe you could ask for the path variable, and loop over it

* "kpsewhich --show-path-name" doesn't help much:
  * It's not available in library "kpse".
  * It contains unwanted stuff (!!, //, ...)
* kpse.expand_path (kpsewhich --expand-path)
  does not expand extra colons:
    texmf.cnf: TEXMFSCRIPTS=$TEXMF/scripts//
  then
    TEXMFSCRIPTS=.: kpsewhich --expand-path '$TEXMFSCRIPTS'
  only returns
    .
* No ls-R lookup.

> there's also luainputs

I don't see, how it could help here.

> > Perhaps a search path could be hacked by using the output of
> >   kpsewhich --show-path=texmfscripts
> > and appending the module directories to each path component.
> > But:
> > * LuaTeX's kpse library doesn't have a "show_path" function.
> > * os.execute is not available in safer mode.
> > * Last but not least, a kpse function is missing for
> >   searching along the modified path specification.
> 
> can't you use lua for that?

Reimplementing kpse library in Lua with analyzing texmf.cnf
files, path expansion, ls-R lookup, ...?

> > * Portability among different operating systems.
> >   (directory specificator, ..., LUA_DIRSEP isn't available, ...)
> > 
> > Ideas?
> 
> we explicitly didn't hard code these things because each user and/or 
> macro package may want to do it different (the same for suffixes of lua 
> files)

The other file types are covered: TeX files, tfm files, type 1 files, ...
Missing is a proper support for lua scripts.

A user/macro writer says for example:
  \documentclass{article}
  \usepackage{longtable}
  \usepackage[T1]{fontenc}
  \usepackage{lmodern}
But he doesn't implement a search algorithm for
finding article.cls or longtable.sty or the latin modern fonts.

Also Lua has a module system, thus a user/macro writer wants to write:
  \directlua0{
    require("foobar.hello")
    -- ...
  }
without implementing, how the module is found.

Lua provides four search strategies by default.
These can be changed and exended, see the table "package.loader"
(latest Lua docu for 5.1)

> > Something like "foobar_hello.lua" isn't the best solution:

Currently I am using
  TDS:scripts/foobar/foobar.hello.lua
This doesn't follow Lua's conventions (TDS:scripts/foobar/hello.lua).
But the search is easier:

  function kpse.module_loader(module)
    local script = module .. ".lua"
    local file = kpse.find_file(script, "texmfscripts")
    if file then
      local loader, error = loadfile(file)
      if loader then
        return loader
      end
      return "\n\tKPSE loading error:\n" .. error
    end
    return "\n\tKPSE search failed"
  end
  table.insert(package.loaders, kpse.module_loader)

and avoids at least:
> > * It doesn't scale well, e.g. it pollutes "package.loaded".

Yours sincerely
  Heiko <oberdiek at uni-freiburg.de>