Async filters not working since 29 Apr

Just today I updated nunjucks in one of my apps. In particular, I was using Async filters, but they have stopped working completely, failing to output anything in place.

env.addFilter('test', function(obj, callback) {
    setTimeout(function() {
        callback(null, 'FOO');
    }, 1000);
}, true);

Strangely, the following does work (but this is besides the point):

env.addFilter('test', function(obj, callback) {
    callback(null, 'FOO');
}, true);

I was able to pinpoint the issue to this commit:

https://github.com/mozilla/nunjucks/commit/9e160e8d13bda3830e5799f75ed02ccb53550fdd

Whereas the following commit is still fine:

https://github.com/mozilla/nunjucks/commit/eadeb67deaf1f805ef34f953391e52503bc09273

I noticed that there are no tests to validate async filter behavior, which probably explains why it went unnoticed for so long … @jlongster care to take a look, please? Thanks!

[ArmorDarks]

Well, tested this out. It works. You need to ensure, that you’re using async renderer:

const nunjucks = require('nunjucks')

const env = nunjucks.configure()

env.addFilter('timout', ({ message, delay }, done) => {
  setTimeout(() => {
    console.log(message)
    done(null, message)
  }, delay)
}, true)

// it should use `(error, result)` callback, otherwise it will work in sync mode
env.render('source/templates/index.nj', {}, (error, result) => {
  console.log(error)
  console.log(result)
})

[callumlocke]

Any progress on this?