Error: can't find 'dust' module when rendering dust templates on node.js

I'm starting with the boilerplate code express generates for me. I'm requiring dustjs-linkedin and compiling some simple templates in app.js like so:

var dust = require('dustjs-linkedin');...

app.set('view engine', 'dust');...

var compiled = dust.compile("Hello {name}!","intro");
// add into dust.cache manually
dust.loadSource(compiled);
console.log(dust.cache);

dust.render("intro", {name: "Fred"}, function(err, out) {
  if(err){console.log(err)}
  console.log(out);
});

This is all works well and I see the HTML outputted in my terminal. Its only when I try and do the same thing from within a route when I start getting this error:

GET / 500 11.607 ms - 904 Error: Cannot find module 'dust'

app.get('/', function(req, res){
  var compiled = dust.compile("Hello {name}!", "intro");
  dust.loadSource(compiled)
  dust.render("intro", {name: "Fred"}, function(err, out) {
    console.log(out);
    res.send(out);
    res.close();
  });
});

This is all within app.js, only it works outside of a route, but not when I move it into a route callback. Does anyone know why it can't find 'dust'? I've required it and it should be visible from within the callback right?

Thanks for any help!

Edit 1 As per the comment below, 'dust' is getting required somewhere. I'm not doing it in my code; my guess is that Express is doing it behind the scenes because my templates have '.dust' file ending. I just tried deleting all my templates (wasn't using them anyways) and now I just get this error:

Error: Failed to lookup view "error" in views directory

All I want is to see the output: "Hello Fred"

Edit 2: I think I found what was wrong

Everything Interrobang posted is correct. The problem, I think, was this middleware block that was generated for me by express-generator:

app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

So for every request, this middleware would fire and throw an error. I'm not 100% sure what its doing but if I comment it out, everything works. My secondary question now, if I may have one, is what exactly is going on and why is it set for all requests?

Solution

You're setting the view engine to dust, but you haven't registered an engine with Express to tell it how to render Dust-- and Express can't do it by default.

Consider using consolidate, hoffman, or adaro (among others) as your Dust rendering engine for Express.

Here's a complete example using consolidate. I have tested and this works on my machine.

var express = require('express'),
    cons = require('consolidate'),
    app = express();

// assign the dust engine to .dust files 
app.engine('dust', cons.dust);

// set .dust as the default extension 
app.set('view engine', 'dust');
app.set('views', __dirname + '/views');

app.get('/', function(req, res) {
    res.render('index', { name: 'Interrobang' });
});

app.listen(3000, function () {
  console.log('Visit http://localhost:3000 woo!');
});

Alternatively, simply remove the view engine line from your code. You're not using Express to do the rendering, so Express doesn't even need to know.

Here's a very simple example without any view engine that I've tested to work. Your Dust templates go in a folder called views.

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

    dust = require('dustjs-helpers');

dust.config.whitespace = true;

dust.onLoad = function(tmpl, cb) {
  fs.readFile(path.join('./views', path.resolve('/', tmpl + '.dust')),
              { encoding: 'utf8' }, cb);
};

var app = express();
app.get('/', function (req, res) {
  dust.stream("hello", { "world": "World!" }).pipe(res);
});

app.listen(3000, function () {
  console.log('Visit http://localhost:3000 woo!');
});