amp-bind: Spurious verify warnings for [height]

[scott-rothman]

What's the issue?

Development mode throws the following error amp-bind: Default value for [height] does not match first expression result (550). This can result in unexpected behavior after the next state change. even though the default value is in fact the same as the first expression result

How do we reproduce the issue?

1. Set an amp-carousel to have a dynamic height via [height]
2. Define the height to the appropriate default value
3. Load the page in development mode and observe the console

My specific example:

<amp-carousel
   [height]="visible ? 720 : 550"
   height="550"
   width="400"
   layout="responsive"
   type="slides">
    <div class="carousel__slide">
       <p>Text content here</p>
       <button [text]="visible ? 'See Less' : 'See More'" 
           on="tap:AMP.setState({visible: !visible})">See More</button>
       <ul [class]="visible ? 'show' : 'hide'" class="hide">
          <li>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</li>
          <li>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</li>
          <li>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</li>
       </ul>
    </div>
</amp-carousel>

What browsers are affected?

Seemingly all browsers

Which AMP version is affected?

Version 1509747505247

[scott-rothman]

Addendum: I discussed this in the amphtml slack channel and was requested to file an issue

[aghassemi]

/to @choumx Issues seems to be with verifyBinding_ which other than text and class seems to assume everything else is a boolean attribute. The bug does not impact actual behaviour, just wrong logging in development mode.

[dreamofabear]

Thanks for filing this issue. This message is actually just a warning, though it has been confusing for many others too. We'll fix this and clarify the messaging.

[dreamofabear]

Fixed by #13236.