Manage library and external dependency folders in your Node.JS project.

setup.js

//// setup.js -- add packages to require.paths
///
/// Manage library folders and external dependency folders in your
/// project by including setup.js in your project.  Call it from the
/// beginning of your project's entry-point to adjust require.paths.
///
/// For example, if you're making an application structured like this:
///
///     README
///     app.js  # main program
///     ext/    # third-party libraries, git submodules, etc.
///     lib/    # your code
///
/// Drop setup.js into ext and add this as the first line of app.js:
///
///     require('./ext/setup').app(__dirname);
///
/// Now anything in lib or ext is fully accessible.  If your
/// project is a library rather than an application, it might be
/// structured this way:
///
///     README
///     ext/
///     lib/mylib.js
///     lib/mylib/
///
/// Put setup.js into ext, then make this the first line of mylib.js:
///
///     require('../ext/setup').app(__dirname + '/..');
///
/// Don't forget to node-waf any C++ extensions in ext!

var fs = require('fs'),
    path = require('path');

exports.app = app;
exports.lib = lib;
exports.ext = ext;
exports.run = run;


/// --- Methods

var run = require;

// A shortcut for adding `lib' and `ext' subfolders, then running a
// main program.
function app(base, main) {
  lib(path.join(base, 'lib'));
  ext(path.join(base, 'ext'));
  return main ? run(path.join(base, main)) : exports;
}

// Local libraries
function lib(folder) {
  if (exists(folder))
    require.paths.unshift(folder);
  return exports;
}

// Third-party libraries
function ext(folder) {
  if (!exists(folder))
    return exports;

  // Some programmers refer to third-party libraries in a fully-qualified manner.
  require.paths.unshift(folder);

  fs.readdirSync(folder).forEach(function(name) {
    var base = path.join(folder, name),
        linked = false;

    // Pure-JS packages have a `lib' folder with LIBRARY.js files in it.
    // Packages with C++ bindings will have a `build/default' folder
    // with LIBRARY.node files in it after running node-waf.
    [path.join(base, '/build/default'), path.join(base, '/lib')]
      .forEach(function(folder) {
        if (exists(folder)) {
          require.paths.unshift(folder);
          linked = true;
        }
      });

    // If neither `lib' or `build' were found, fallback to linking the
    // folder itself.
    if (!linked)
      require.paths.unshift(base);
  });
  return exports;
}


/// --- Aux

function exists(filename) {
  try {
    fs.statSync(filename);
    return true;
  } catch (x) {
    return false;
  }
}