Loading routes do not work in FastBoot

I get the following error in my app:

There was an error running your app in fastboot. More info about the error: 
 Error: a glimmer transaction was begun, but one already exists. You may have a nested transaction
    at debugAssert (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/@glimmer/util.js:62:1)
    at Environment.begin (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/@glimmer/runtime.js:6378:1)
    at Environment.begin (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/ember-glimmer/environment.js:273:1)
    at InertRenderer._renderRoots (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/ember-glimmer/renderer.js:311:1)
    at InertRenderer._renderRootsTransaction (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/ember-glimmer/renderer.js:379:1)
    at InertRenderer._revalidate (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/ember-glimmer/renderer.js:418:1)
    at invokeWithOnError (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/backburner.js:281:1)
    at Queue.flush (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/backburner.js:152:1)
    at DeferredActionQueues.flush (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/backburner.js:343:1)
    at Backburner.end (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/backburner.js:451:1)
    at Timeout.Backburner._boundAutorunEnd [as _onTimeout] (.../tmp/broccoli_merge_trees-output_path-Y53V5i2J.tmp/assets/backburner.js:413:1)
    at ontimeout (timers.js:469:11)
    at tryOnTimeout (timers.js:304:5)
    at Timer.listOnTimeout (timers.js:264:5)

At first I thought liquid-fire (#530) was causing this. But after removing liquid-fire I got the error above.

[topaxi]

I could reproduce the error mentioned in the liquid-fire issue #530.

git clone https://github.com/topaxi/fastboot-loading-states
cd fastboot-loading-states
ember s

FastBoot console output upon visit:

There was an error running your app in fastboot. More info about the error: 
 TypeError: Cannot read property 'createComment' of undefined
    at ListBlockOpcode.evaluate (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/@glimmer/runtime.js:6759:1)
    at UpdatingVM.execute (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/@glimmer/runtime.js:6495:1)
    at RenderResult.rerender (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/@glimmer/runtime.js:6853:1)
    at RootState._this.render (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/ember-glimmer/renderer.js:69:1)
    at exports.runInTransaction (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/ember-metal.js:674:1)
    at InertRenderer._renderRoots (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/ember-glimmer/renderer.js:341:1)
    at InertRenderer._renderRootsTransaction (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/ember-glimmer/renderer.js:379:1)
    at InertRenderer._revalidate (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/ember-glimmer/renderer.js:418:1)
    at invokeWithOnError (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/backburner.js:281:1)
    at Queue.flush (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/backburner.js:152:1)
    at DeferredActionQueues.flush (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/backburner.js:343:1)
    at Backburner.end (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/backburner.js:451:1)
    at Timeout.Backburner._boundAutorunEnd [as _onTimeout] (/home/dsenn/gitty/github/fastboot-loading-states/tmp/broccoli_merge_trees-output_path-wTqgLUnw.tmp/assets/backburner.js:413:1)
    at ontimeout (timers.js:469:11)
    at tryOnTimeout (timers.js:304:5)
    at Timer.listOnTimeout (timers.js:264:5)

I’m not sure how closely related this is to my specific case though as I’ve been unable to reproduce the crash I got once I remove liquid-fire from my actual app.

[CvX]

Here’s a minimal bug repro. Took a couple of days, I’ve been taking away parts of a production app until only this was left:

// routes/application.js
import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';
import { next } from '@ember/runloop';
import RSVP from 'rsvp';

export default Route.extend({
  fastboot: service(),

  model() {
    let deferred = RSVP.defer();
    if (this.get('fastboot.isFastBoot')) {
      this.get('fastboot').deferRendering(deferred.promise);
    }

    let controller = this.controllerFor(this.routeName);
    controller.set('data', [1]);

    next(() => {
      controller.set('data', [2]);
      deferred.resolve();
    });
  }
});

// controllers/application.js
import Controller from '@ember/controller';

export default Controller.extend({
});

{{!-- templates/application.js --}}
{{#each data}}
{{/each}}

• ember-cli-fastboot in devDependencies