Using LuaLaTeX and SQLite3

It is possible to modify the package loading mechanism in Lua. In the case of LuaTeX, the kpse library is used to load modules instead of the default mechanism that uses package.path and package.cpath. So setting these variables will not have any effect. But nothing prevents us from using both methods using a Lua module, lualoader.lua. Save the snippet below as a file in the directory containing your document:

-- lualoader.lua
-- this is copied from luatexbase.loader
local make_loader = function(path, pos, loadfunc)
  local default_loader = package.searchers[pos]
  local loader = function(name)
    local file, _ = package.searchpath(name,path)
    if not file then
      local msg = "\n\t[lualoader] Search failed"
      local ret = default_loader(name)
      if type(ret) == "string" then
        return msg ..ret
      elseif type(ret) == "nil" then
        return msg
      else
        return ret
      end
    end
    local loader,err = loadfunc(file, name)
    if not loader then
      return "\n\t[lualoader] Loading error:\n\t"..err
    end
    return loader
  end
  package.searchers[pos] = loader
end

local binary_loader = function(file, name)
  local symbol = name:gsub("%.","_")
  return package.loadlib(file, "luaopen_"..symbol)
end

make_loader(package.path,2,loadfile)
make_loader(package.cpath,3, binary_loader)

We use the function make_loader to insert a function searching package.path or package.cpath at a specified index in the package.searchers table. 2 for lua files, 3 for binary modules. We also need to use different functions to load a module depending on its type. We use loadfile for Lua files and slightly more complicated function for binary modules that uses package.loadlib.

As an example, we can try loading lsqlite3 from LuaTeX:

\documentclass{article}
\directlua{
require "lualoader"
}

\usepackage{fontspec}
\usepackage[english]{babel}
\begin{document}
\directlua{%
local sqlite3 = require("lsqlite3")

local db = sqlite3.open_memory()

db:exec[[
  CREATE TABLE test (id INTEGER PRIMARY KEY, content);

  INSERT INTO test VALUES (NULL, 'Hello World');
  INSERT INTO test VALUES (NULL, 'Hello Lua');
  INSERT INTO test VALUES (NULL, 'Hello Sqlite3')
]]

for row in db:nrows("SELECT * FROM test") do
  tex.print(row.id .. " : ".. row.content )
end

}
\end{document}

which yields:

enter image description here

Edit:

As Uwe pointed out, luarocks as installed by some Linux package managers may not work correctly. I experienced this on Fedora, so I installed luarocks from source. Another solution may be to set package.path and package.cpath to the directories listed by the command 

luarocks path

On my own system, this yields:

$ luarocks path
export LUA_PATH='/home/michal/.luarocks/share/lua/5.2/?.lua;/home/michal/.luarocks/share/lua/5.2/?/init.lua;/usr/local/share/lua/5.2/?.lua;/usr/local/share/lua/5.2/?/init.lua;/usr/share/lua/5.2/?.lua;/usr/share/lua/5.2/?/init.lua;/usr/lib/lua/5.2/?.lua;/usr/lib/lua/5.2/?/init.lua;./?.lua'
export LUA_CPATH='/home/michal/.luarocks/lib/lua/5.2/?.so;/usr/local/lib/lua/5.2/?.so;/usr/lib/lua/5.2/?.so;/usr/lib/lua/5.2/loadall.so;./?.so'

So a modified preamble would be:

\directlua{    
package.cpath = '/home/michal/.luarocks/lib/lua/5.2/?.so;/usr/local/lib/lua/5.2/?.so;/usr/lib/lua/5.2/?.so;/usr/lib/lua/5.2/loadall.so;./?.so'
package.path = '/home/michal/.luarocks/share/lua/5.2/?.lua;/home/michal/.luarocks/share/lua/5.2/?/init.lua;/usr/local/share/lua/5.2/?.lua;/usr/local/share/lua/5.2/?/init.lua;/usr/share/lua/5.2/?.lua;/usr/share/lua/5.2/?/init.lua;/usr/lib/lua/5.2/?.lua;/usr/lib/lua/5.2/?/init.lua;./?.lua'
require "lualoader"
}

As of May 2017, there is a package on CTAN called luapackageloader, that allows you to modify the default package searching behavior in LuaTeX.

Once you load luapackageloader, doing a require will first try the default kpse based searcher. If the module isn’t found, it will also try to load the package from Lua’s package.path and package.cpath values.

Usage example

\documentclass{article}    
\usepackage{luacode}
\usepackage{luapackageloader}

\begin{document}

\begin{luacode*}
  package.path="/usr/local/lib/luarocks/rocks;/usr/local/lib/luarocks/rocks/lsqlite3; 
  /usr/local/lib/lua/5.1/lsqlite3.so" .. package.path

  require("lsqlite3")
\end{luacode*}

Hello Lua!

\end{document}

Additional note: you can do eval $(luarocks path) on your shell to set the package path using environment variables which the Lua interpreter will pick up automatically. That way, you do not need to fiddle with the package.path yourself.

Tags:

Luatex

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