vault/ui/app/components/message-error.js

import { computed } from '@ember/object';
import Component from '@ember/component';

export default Component.extend({
  model: null,
  errors: computed(function() {
    return [];
  }),
  errorMessage: null,

  displayErrors: computed(
    'errorMessage',
    'model.{isError,adapterError.message,adapterError.errors.@each}',
    'errors',
    'errors.@each',
    function() {
      const errorMessage = this.get('errorMessage');
      const errors = this.get('errors');
      const modelIsError = this.get('model.isError');
      if (errorMessage) {
        return [errorMessage];
      }

      if (errors && errors.length > 0) {
        return errors;
      }

      if (modelIsError) {
        if (this.get('model.adapterError.errors.length') > 0) {
          return this.get('model.adapterError.errors');
        }
        return [this.get('model.adapterError.message')];
      }
    }
  ),
});