Templates script[type=text/plain] are removed if "id" attribute is added

[grapheon]

Bug Description

If add "id" attribute to template like <script id="my-template" type="text/plain" template="amp-mustache">...</template> to refer to it, for example from <amp-list>, the plugin will completely remove this template from the resulting code.

Expected Behaviour

Provide "id" attribute support for templates like <script id="my-template" type="text/plain" template="amp-mustache">...</template>.

Steps to reproduce

1. Add code to AMP page:

<script type="text/plain" template="amp-mustache">
    <h2>Plain template</h2>
</script>
<script id="my-template" type="text/plain" template="amp-mustache">
    <h2>Referenced template</h2>
</script>

2. View the resulting source code for an AMP page.
3. Make sure the <script id="my-template" type="text/plain" template="amp-mustache">...</template> is missing.

Please also see issue #26676.

Additional context

• WordPress version: 5.3.2
• Plugin version: 1.4.2
• AMP plugin template mode: Website; Standard; Serve all templates as AMP regardless of what is being queried.
• PHP version: 7.3.11

Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[westonruter]

@spasibych Your markup seems malformed:

<script type="text/plain" template="amp-mustache">
    <h2>Plain template</h2>
</template>
<script id="my-template" type="text/plain" template="amp-mustache">
    <h2>Referenced template</h2>
</template>

Should it not rather be:

<script type="text/plain" template="amp-mustache">
    <h2>Plain template</h2>
</script>
<script id="my-template" type="text/plain" template="amp-mustache">
    <h2>Referenced template</h2>
</script>

Note </script> rather than </template> should be used.

[grapheon]

@westonruter is my mistake, i'm sorry.

Now I tried it and it works. Maybe something from "blacklisted_value_regex" got in the way earlier.