tools: Vulcanize doesn't understand ES6 class-based declarations that use `beforeRegister` to set `is`

It seems that vulcanize is currently not correctly finding out the name (the is attribute) of the Polymer elements definition written as an ES6/ES2015 Class. When multiple elements definition as classes are present we get the following error/warning printed for each additional elements:

Ignoring duplicate element definition: undefined

Below is the minimal source file to replicate the issue:

my-element.html

<html>
<head>
  <link rel="import" href="bower_components/polymer/polymer.html">
</head>
<body>
<dom-module id="my-element">
  <template>
    <div>Hello World</div>
  </template>

</dom-module>
<script>
  class MyElement {
    beforeRegister() {
      this.is = 'my-element';
    }
  }
  Polymer(MyElement);

  class MyElement2 {
    beforeRegister() {
      this.is = 'my-element-2';
    }
  }
  Polymer(MyElement2);

  class MyElement3 {
    beforeRegister() {
      this.is = 'my-element-3';
    }
  }
  Polymer(MyElement3);
</script>
</body>
</html>

Then run vulcanize my-element.html > /dev/null and you’ll get the following output on the console:

Ignoring duplicate element definition: undefined
Ignoring duplicate element definition: undefined

About this issue

Original URL
State: closed
Created 9 years ago
Comments: 19 (9 by maintainers)

Most upvoted comments

@mtsgrd Still not fixed apparently 😃 You can work around it since typically you’d need to transpile your ES6 code to ES5 with Babel.js to obtain large browser support. And ES5 code is not impacted.

nicolasgarnier on Nov 3, 2016