Firing value-changed should not cause repeated value change on element itself

[nazar-pc]

Description

I've created small behavior for myself to simplify data binding to type-extension element input[is=cs-input-text] like following:

Polymer.cs.behaviors.value = {
  listeners: {
    change: '_changed',
    input: '_changed'
  },
  _changed: function(){
    this.fire('value-changed');
  }
};

The idea is that:

<!-- Now I'm able to write following -->
<input is="cs-input-text" value="{{value}}">
<!-- instead of -->
<input is="cs-input-text" value="{{value::input}}">

However, Polymer overrides input.value with the same value when data-binding goes downwards and causes cursor to move from its current position to the end of the text.

Live Demo

https://jsbin.com/juvimisefu/1/edit?html,output

Steps to Reproduce (on Demo)

1. Put cursor inside of ><
2. Type single character

Expected Results

Cursor remains right after typed character

Actual Results

Cursor moved to the end of the text

Browsers Affected

• Chrome
• Firefox
• Edge
• Safari 9
• Safari 8
• IE 11

Versions

• Polymer: v1.4.0
• webcomponents: v0.7.22

[nazar-pc]

Fix is provided in PR #3678