I have an error when implement AppLocalizeBehavior in LitElement

[Juan Lorenzo Llanes]

Hi everyone

I'm working whith pwa-starter-kit LitElement and AppLocalizeBehavior and I have the following error when I implement AppLocalizeBehavior in LitElement app

---package.json ---

"dependencies": {
    "@polymer/app-layout": "^3.0.0",
    "@polymer/app-localize-behavior": "^3.0.1",
    "@polymer/polymer": "^3.1.0",
    "@webcomponents/webcomponentsjs": "^2.2.4",
    "lit-element": "^2.0.0-rc.3",
    "pwa-helpers": "^0.9.0",
    "redux": "^4.0.0",
    "redux-thunk": "^2.3.0",
    "reselect": "^4.0.0"
  },
  "devDependencies": {
    "@polymer/test-fixture": "^4.0.2",
    "axe-core": "^3.0.0",
    "chai": "^4.1.2",
    "del": "^3.0.0",
    "gulp": "^4.0.0",
    "gulp-rename": "^1.3.0",
    "gulp-replace": "^1.0.0",
    "mocha": "^5.2.0",
    "pixelmatch": "^4.0.2",
    "polymer-cli": "^1.9.3",
    "polyserve": "^0.27.0",
    "prpl-server": "^1.4.0",
    "puppeteer": "^1.5.0",
    "wct-mocha": "^1.0.0"
  }

--- old my-app.js--

class MyApp extends connect(store)(LitElement) {
    ....

---AppLocalizeBehavior my-app.js ---

import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
import {AppLocalizeBehavior} from '@polymer/app-localize-behavior/app-localize-behavior.js';




class MyApp extends connect(store)(mixinBehaviors([AppLocalizeBehavior],LitElement)) {
 .....

----- ERROR--------------

 

updating-element.ts:487 Uncaught TypeError: Cannot read property 'forEach' of undefined
    at HTMLElement._saveInstanceProperties (updating-element.ts:487)
    at HTMLElement.initialize (updating-element.ts:467)
    at HTMLElement.initialize (lit-element.ts:130)
    at new UpdatingElement (updating-element.ts:230)
    at new LitElement (lit-element.ts:76)
    at new PropertiesChanged (properties-changed.js:170)
    at new PropertyAccessors (property-accessors.js:115)
    at new TemplateStamp (template-stamp.js:125)
    at new PropertyEffects (property-effects.js:1195)
    at new PropertiesMixin (properties-mixin.js:115)

Thanks in advance

[Justin Fagnani]

Polymer Behaviors are a Polymer-specific abstraction, and you can't apply them to non-Polymer elements even as a mixin because they assume certain API from the base class that LitElement doesn't provide.

I don't know much about AppLocalizeBehavior for FormatJS, but in this case I think you should be able to use FormatJS directly.

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