You attempted to access the __DESCRIPTOR__ property (of <frontend@service:prototypes::ember581>)

[sly7-7]

Related to #16148

I have a service, injected in a route (extending the AuthenticatedRouteMixin). When I do this.get('prototypes'),so, in my use case I don't know if the error is coming from:

• The route accessing a service
• The route itself
• The service itself

Let me now if you need more information.
For now, I will try to revert 2.18 (ember 3.0.X seems to have problems with ie 11)

There is more information at https://github.com/emberjs/ember.js/issues/16148, and
you can help us improve this error message by telling us more about what happened in
this situation.
    at new EmberError (error.js:40)
    at assert (index.js:139)
    at Object.get (core_object.js:57)
    at isDescriptorTrap (ember-metal.js:3258)
    at get (ember-metal.js:3430)
    at Class.get (observable.js:38)
    at route.js:62

cc/ @wycats
Maybe this is an issue in ember-simple-auth, so kindly cc/ to @marcoow

[btecu]

Do you have any unknownProperty or setUnknownProperty?

[sly7-7]

In my service, yes, I have an unknownProperty function. Actually I had merely copy-paste the code from https://github.com/kategengler/ember-feature-flags/blob/master/addon/services/features.js which also have an unknowProperty function

[wycats]

@sly7-7 can you paste the whole error message, including the details about which properties are involved?

[sly7-7]

ember-console.js:29 Error while processing route: widget-group.index Assertion Failed: You attempted to access the `__DESCRIPTOR__` property (of <frontend@service:prototypes::ember579>).
Since Ember 3.1, this is usually fine as you no longer need to use `.get()`
to access computed properties. However, in this case, the object in question
is a special kind of Ember object (a proxy). Therefore, it is still necessary
to use `.get('__DESCRIPTOR__')` in this case.

If you encountered this error because of third-party code that you don't control,
there is more information at https://github.com/emberjs/ember.js/issues/16148, and
you can help us improve this error message by telling us more about what happened in
this situation. Error: Assertion Failed: You attempted to access the `__DESCRIPTOR__` property (of <frontend@service:prototypes::ember579>).
Since Ember 3.1, this is usually fine as you no longer need to use `.get()`
to access computed properties. However, in this case, the object in question
is a special kind of Ember object (a proxy). Therefore, it is still necessary
to use `.get('__DESCRIPTOR__')` in this case.

If you encountered this error because of third-party code that you don't control,
there is more information at https://github.com/emberjs/ember.js/issues/16148, and
you can help us improve this error message by telling us more about what happened in
this situation.
    at new EmberError (http://localhost:4200/assets/vendor.js:25254:25)
    at assert (http://localhost:4200/assets/vendor.js:25497:15)
    at Object.get (http://localhost:4200/assets/vendor.js:50711:73)
    at isDescriptorTrap (http://localhost:4200/assets/vendor.js:37443:87)
    at get (http://localhost:4200/assets/vendor.js:37615:41)
    at Class.get (http://localhost:4200/assets/vendor.js:49512:34)
    at http://localhost:4200/assets/frontend.js:10830:18
    at tryCatcher (http://localhost:4200/assets/vendor.js:62499:21)
    at invokeCallback (http://localhost:4200/assets/vendor.js:62671:33)
    at publish (http://localhost:4200/assets/vendor.js:62657:9)

Concerning the involved properties It's hard to say. The error is thrown when I access the prototypes service from the afterModel hook of a route. Just this.get('prototypes') make the app crash.
Here is the code of the service if it helps (BTW Thanks to @kategengler for her addon).

import { camelize } from '@ember/string';
import { keys } from '@ember/polyfills';
import EmberObject from '@ember/object';
import Service from '@ember/service';

export default Service.extend({
  flags: EmberObject.create(),

  setup(flags) {
    var normalizedFlags = {};
    for (var flag in flags) {
      if (flags.hasOwnProperty(flag)) {
        normalizedFlags[this._normalizeFlag(flag)] = flags[flag];
      }
    }
    this.set('flags', EmberObject.create(normalizedFlags));
  },

  showAll() {
    return this.get('flags').getProperties(keys(this.get('flags')));
  },

  enable(flag) {
    var normalizedFlag = this._normalizeFlag(flag);
    this.get('flags').set(normalizedFlag, true);
    this.notifyPropertyChange(normalizedFlag);
  },

  enableAll() {
    keys(this.get('flags')).forEach(function(flag) {
      this.enable(flag);
    }, this);
  },

  disable(flag) {
    var normalizedFlag = this._normalizeFlag(flag);
    this.get('flags').set(normalizedFlag, false);
    this.notifyPropertyChange(normalizedFlag);
  },

  disableAll() {
    keys(this.get('flags')).forEach(function(flag) {
      this.disable(flag);
    }, this);
  },

  unknownProperty(key) {
    return this.enabled(key);
  },

  enabled(flag) {
    var normalizedFlag = this._normalizeFlag(flag);
    return !!this.get('flags').get(normalizedFlag);
  },

  _normalizeFlag(flag) {
    return camelize(flag);
  }
});

[rwjblue]

In this case, the proxy's unknownProperty always returns a value (either true or false AFAICT). This will always trigger the proxy assertion when accessing properties that are not properties of the proxy itself.

[rwjblue]

Submitted a fix in #16274

[sly7-7]

Thanks a lot @rwjblue ❤️