Tools: linter warns on item property of vaadin-grid templates

[bennypowers]

<vaadin-grid> uses the keyword item to represent iterated data points in it's grid templates, like so

  <vaadin-grid aria-label="Two-way Binding Example" items="[[users.result]]">

    <vaadin-grid-column>
      <template class="header">First Name</template>
      <template>
        <input value="{{item.firstName::input}}" readonly$="[[!editing]]">
      </template>
    </vaadin-grid-column>

    <vaadin-grid-column>
      <template class="header">Last Name</template>
      <template>
        <input value="{{item.lastName::input}}" readonly$="[[!editing]]">
      </template>
    </vaadin-grid-column>

    <vaadin-grid-column width="200px">
      <template class="header">Email</template>
      <template>
        <div>[[item.firstName]].[[item.lastName]]@example.com</div>
      </template>
    </vaadin-grid-column>

  </vaadin-grid>

The above example does not trigger linting errors, however, if [[item.prop]] is bound in a child template, polymer linter warns.

<vaadin-grid id="grid" name="grid" items="[[videos]]">

<vaadin-grid-column flex-grow="2">
  <template class="header">Title</template>
  <template>
    <span class="title">[[item.videoData.title]]</span>
    <template is="dom-if" if="[[!same(item.videoData.title, item.videoData.filename)]]" restamp="true">
      <span class="filename">[[item.videoData.filename]]</span>
    </template>
  </template>
</vaadin-grid-column>

in which case, the binding expression [[item.videoData.filename]] triggers a warning. item is not declared or used more than once.`

[stramel]

I'm also getting

      aria-label="[[gridDescription]]"
      ~~~~~~~~~~

mtz-group-list.html(33,6) warning [set-unknown-attribute] - vaadin-grid elements do not have a property named ariaLabel. Consider instead:  aria-label$

[web-padawan]

Please see #67

[stramel]

Hmmm #67 looks similar to the items issue however ariaLabel piece seems unrelated?

[web-padawan]

aria-label is not a property and therefore you should use attribute binfing there

[stramel]

You're right, maybe a better error message would be more useful.

[bennypowers]

I have the same error with this syntax:

<template is="dom-repeat" items="[[array]]" as="clipset" index-as="index">
  <paper-listbox name$="[[_getClipsetName(index, clipsets)]]" selected="{{clipIndex}}">
    <template is="dom-repeat" items="[[clipset]]" as="clip" index-as="makesError">
      <paper-item id="[[clip.id]]" on-tap="_handleTap">
        <span class="index">[[makesError]]</span>

[bennypowers]

For anyone arriving from Google, welcome 👋

In the meantime, I've disabled these warnings in CI by defining my lint script in my PSK app's package.json as such:

"lint": {
  "rules": ["polymer-2-hybrid"],
  "ignoreWarnings": ["databind-with-unknown-property"]
},

[jarrodek]

I'm not sure if this is the same issue but I'm having similar error message when using template inside another template.
Iron list uses <template> to generate list item and inside this template I am using item property that is used inside another template:

<iron-list>
  <template>
    <div>
      <span>[[item.property]] - this works here fine</span>
      <template is="dom-if" if="[[item.property]]">
         <span>[[item.property]] - this works here too but linter shows error</span>
      </template>
    </div>
  </template>
<iron-list>

[stale[bot]]

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