Bug: TypeError when setting on property as interpolated string

[mlamowski]

Description

Attempting to set the property on using an interpolated string value (e.g. from a function like when()) results in a TypeError regarding addEventListener.

Steps to Reproduce

1. The component has a string property named on:

properties() {
        return {
            on: '', // '' || 'default'
        };
    }

2. Failing Syntax:
<button on="${when(condition, 'default', '')}">...</button>

3. Error Logged:
Uncaught (in promise) TypeError: Failed to execute 'addEventListener' on 'EventTarget': parameter 2 is not of type 'Object'.

4. Working Syntax:
<button on="default">...</button>
<button .on="${when(condition, 'default', '')}">...</button>

[eddyloewen]

I would bet this line

element-js/src/dom-parts/AttributePart.js

Line 86 in c921a2d

if (name.startsWith('@') || name.startsWith('on')) {

has something to do with it.