Amphtml: AMP Validator considers a reference to template script[type=text/plain] an error

[spasibych]

What's the issue?

When referenced from <amp-list ... template="my-template"></amp-list> to <script id="my-template" type="text/plain" template="amp-mustache"> ... </template> AMP Validator showing error "Attribute 'template' in tag 'amp-list' contains a value that does not match any other tags on the page".

However, everything will work, but the page will be deleted from Google AMP Cache due to this error.

How do we reproduce the issue?

1. Add code to AMP page:

<amp-state id="items"><script type="application/json">[]</script></amp-state>
<button on="tap:AMP.setState({ items: items.splice(items.length, 0, items.length) })">Add item</button>
<template id="items-template" type="amp-mustache"><code>{{#.}}, {{/.}}{{.}}</code></template>
<script id="items-scripted" type="text/plain" template="amp-mustache"><code>{{#.}}, {{/.}}{{.}}</code></script>
<amp-list [src]="items" items="." layout="fixed-height" height="32" template="items-template"></amp-list>
<amp-list [src]="items" items="." layout="fixed-height" height="32" template="items-scripted"></amp-list>

1. View the AMP page.
2. See AMP Validator errors.

AMP Validator will point to a line with amp-list referring to the template script[type=text/plain] by id items-scripted. However, everything will work.

Source and Screenshots

Source test script: amp-mustache.html.zip

[banaag]

cc @ampproject/wg-caching

[twifkak]

Sorry for the delay. Here's a minimal test case.

This requirement was added in #24267 (from http://cl/264646527); it seems it was too strict.

The solution is to add attrs { name: "id" add_value_to_set: TEMPLATE_IDS } inside the script tagspec at https://github.com/ampproject/amphtml/blob/26295bc28d43750dc7fb1550c2b1841426a7ac2b/extensions/amp-mustache/validator-amp-mustache.protoascii#L66

But first we need to make sure that all the dependents know how to find templates in script elements.

[twifkak]

Yes all of amp-date-display 0.1, amp-date-display 0.2, amp-list 0.1, and amp-date-countdown 0.1 seem to support script element templates.

[twifkak]

OK, fix is in master. It may take ~1 week to propagate.

[spasibych]

@twifkak thank you very much!