[core, 4-RC.1] TypeError: A.observe is not a function

[peterpeterparker]

Bug Report

Ionic version:
[x] 4.x - CORE

Current behavior:
When I upgrade my project where I use Ionic Core and the Ionicons from v4-RC.0 to v4-RC.1 I face the following error at runtime:

ionicons.core.js:8 Uncaught TypeError: A.observe is not a function
    at ionicons.core.js:8
    at applyPolyfills (ionicons.core.js:8)
    at r (ionicons.core.js:5)
    at defineCustomElements (ionicons.define.js:8)
    at Module../src/index.js (index.js:24)
    at __webpack_require__ (bootstrap:63)
    at bootstrap:195
    at bootstrap:195

Expected behavior:
No error ;)

Steps to reproduce:

1. npm init deckdeckgo
2. cd yourproject
3. npm install @ionic/core --save
4. npm run start
5. open http://localhost:3000

Ionic info:

Ionic:

ionic (Ionic CLI) : 4.8.0

System:

NodeJS : v11.5.0
npm : 6.5.0
OS : macOS Mojave

Screenshot

Notes

• I tried the dev version, same error
• Is it maybe more a Stencil issue maybe related to defineCustomElements?

[peterpeterparker]

Yep looks like it's a Stencil issue (stenciljs/core#1308), therefore I close this one

[ionitron-bot]

Thanks for the issue! This issue is being locked to prevent comments that are not relevant to the original issue. If this is still an issue with the latest version of Ionic, please create a new issue and ensure the template is fully filled out.