Passing Context objects through express does not work

I’ve been having an extended discussion on StackOverflow (link) with @sethkinast regarding passing Context objects through Express.

I have put together a very quick example of how to replicate this issue here: https://github.com/adamkdean/dust-test

But to save time, the script is this:

const path = require('path')
const hoffman = require('hoffman')
const express = require('express')
const request = require('request')
const duster = require('duster')
const dust = duster.dust

const app = express()
const base = dust.context({
  isBase: true,
  age: 26,
  people: [
    { name: 'exampleA' },
    { name: 'exampleB' }
  ]
})

app.set('views', path.join(__dirname, 'views'))
app.set('view engine', 'dust')
app.engine('dust', hoffman.__express())

app.get('/', function (req, res) {
  res.render('people', {})
})

app.get('/pojo', function (req, res) {
  res.render('people', {
    age: 26,
    people: [
      { name: 'exampleA' },
      { name: 'exampleB' }
    ]
  })
})

app.get('/context', function (req, res) {
  res.render('people', base.push({
    people: [
      { name: 'adam' }
    ]
  }))
})

app.listen(4000, function () {
  console.log('Visit http://localhost:4000 to see streaming!')
})

If you go to /pojo then the plain old JavaScript object renders fine (the template is {#people}<li>{name} aged {age}</li>{/people}), but if you go to /context then it doesn’t render fine at all.

I think this would probably be a better place to discuss the issue.

[sethkinast]

Here’s the issue: https://github.com/expressjs/express/blob/master/lib/application.js#L535

A new object, renderOptions, gets created. This object of course doesn’t have Context as its prototype so Dust tries to shove it into a context.

It’s very interesting that no one has ever run into this before. I would never have expected Express to mangle a context object passed to it. We can fix this by dropping the instanceof check on our end.

[sethkinast]

This is available as 2.7.4.