Allow multiple views roots in Express.js

enableMultipleViewRoots.js

// Usage:
// var express = require('express')
// require('enableMultipleViewRoots')(express)

module.exports = function(express) {
  var old = express.view.lookup;

  function lookup(view, options) {
    // If root is an array of paths, let's try each path until we find the view
    if (options.root instanceof Array) {
      var opts = {}
      for (var key in options) opts[key] = options[key]
      var root = opts.root, foundView = null
      for (var i=0; i<root.length; i++) {
        opts.root = root[i]
        foundView = lookup.call(this, view, opts)
        if (foundView.exists) break
      }
      return foundView
    }

    // Fallback to standard behavior, when root is a single directory
    return old.call(express.view, view, options)
  }

  express.view.lookup = lookup;
}