Monkey-patch node require to support a "packages" key in package.json

patch-node-require.js

// monkey patch for and adaption of node module loader code

// joiner from node/lib/modules.js
var joiner = process.platform === 'win32' ? '\\' : '/';

// allow package default to be overridden
exports.defaultPackageDir = 'node_modules';

exports.patch = function() {

  var fs = require('fs');
  var path = require('path');
  var Module = require('module');
  var packageCache = {};

  function readPackage(requestPath) {
    if (packageCache.hasOwnProperty(requestPath)) {
      return packageCache[requestPath];
    }

    try {
      var jsonPath = path.resolve(requestPath, 'package.json');
      var json = fs.readFileSync(jsonPath, 'utf8');
      // TODO copy partial object to only cache relevant bits
      var pkg = packageCache[requestPath] = JSON.parse(json);
      return pkg;
    } catch (e) {}

    return false;
  }

  // 'from' is the __dirname of the module.
  Module._nodeModulePaths = function(from) {
    // guarantee that 'from' is absolute.
    from = path.resolve(from);

    // note: this approach *only* works when the path is guaranteed
    // to be absolute.  Doing a fully-edge-case-correct path.split
    // that works on both Windows and Posix is non-trivial.
    var splitRe = process.platform === 'win32' ? /[\/\\]/ : /\//;
    var paths = [];
    var parts = from.split(splitRe);
    var packageDir = exports.defaultPackageDir;

    for (var tip = parts.length - 1; tip >= 0; tip--) {
      var dir = parts.slice(0, tip + 1);
      if (tip > 0) {
        var packageMeta = readPackage(dir.join(joiner));
        var packages = packageMeta && packageMeta.packages;
        // packages key can be an array
        if (packages && packages.length) {
          if (typeof packages === 'string') packages = [packages];
          var i = packages.length;
          // loop backward for better paths specifity
          while (i--) {
            var name = normalizeDir(packages[i]);
            paths.push(dir.concat(name).join(joiner));
          }
          // stop now that we've found the package root
          break;
        }
      }

      // don't search in, e.g. node_modules/node_modules
      if (parts[tip] === exports.defaultPackageDir) continue;
      paths.push(dir.concat(exports.defaultPackageDir).join(joiner));
    }

    return paths;
  };
};

function normalizeDir(name) {
  name = name || '';
  var parts = name.split(joiner);
  if (parts.length < 2) return parts[0];
  // allow './' just to be friendly, but throw on everything else
  if (parts.length === 2 && parts[0] === '.') return parts[1];
  throw new Error('Invalid directories key in package.json: ' + name);
}