New Twiddle

controllers.application\.js

import Controller from '@ember/controller';
import {action} from '@ember/object';
import {tracked} from '@glimmer/tracking';

export default class ApplicationController extends Controller {
  @tracked items;
  
  @action 
  updateItems(event) {
    let count = event.target.value;
    
    let items = [];
    for (let i = 1, i <= count; i++) {
      items.push(i);
    }
    
    this.items = items;
  }
}

helpers.load-data\.js

import { helper } from '@ember/component/helper';

export default helper(function loadData([data]) {
  return new Promise((resolve) => {
  	setTimeout(() => resolve(data), 1000);
  });
});

helpers.resolve-promise\.js

import Helper from '@ember/component/helper';
import { inject as service } from '@ember/service';

export default class KpiTypeDescription extends Helper {
  _promise;

  compute([promise]) {
    if(promise === this._promise) {
      return this._value;
    }
    
    this._promise = promise;
    this._value = undefined;
    
    promise.then((value) => {
      this._value = value;
      this.recompute();
    });
  }
}

templates.application\.hbs

<input type="number" {{on "input" this.updateItems}}>

<ItemList @items={{this.items}} />

templates.components.item-list\.hbs

{{#let (load-data @items) as |promise|}}
  {{#let (resolve-promise promise) as |data|}}
    Data: {{data}}
  {{/let}}
{{/let}}

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}