Update spec to include fetchpriority support

[westonruter]

Feature Description

• Update spec once fetchpriority support has landed: AMP Validator: Allow attribute 'fetchpriority' for link tag amphtml#38715 This is done with Update amphtml spec to 2309011827000 #7615.
• Remove obsolete Bento support as noted in Correctly handle siblings_disallowed from spec #7597 (comment)
• Make sure that the image sanitizer passes through fetchpriority.
• Update amp-toolbox-php to dev-master util changes tested and full 11.3 release is made.

Acceptance Criteria

No response

Implementation Brief

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QA Testing Instructions

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Demo

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Changelog Entry

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[westonruter]

• Update spec once fetchpriority support has landed: AMP Validator: Allow attribute 'fetchpriority' for link tag amphtml#38715

This has landed in ampproject/amphtml@49ee0db as part of https://github.com/ampproject/amphtml/releases/tag/2309011827000

[thelovekesh]

Thanks, for the update @westonruter, I will start working on it.

[westonruter]

Looks like the spec update is live, but note it is only for img and not amp-img:

img	amp-img

This makes sense because amp-img is lazy-loaded by the runtime, so it doesn't make sense for the attribute to be on it. The attribute also works for SSR'ed img, which is just what we need:

Lastly, it also works in the noscript > img fallback.

So what we need to do is this:

1. If fetchpriority=high is on an img and the image sanitizer is configured to convert to amp-img, we'll need to remove this attribute from the amp-img since it isn't allowed there. But we will need to remember it was there originally. This could be done with a new data attribute, or we could automatically add the data-hero attribute which the AMP Optimizer uses as a signal to SSR. Another option is the data-hero-candidate which the AMP plugin uses as a hint for what could be a hero.
2. Retain fetchpriority=high on the noscript > img fallback.
3. Update AMP Toolbox to also always SSR any amp-img that originally had a fetchpriority=high on the img. This would be to update the OptimizeHeroImages transformer so that findHeroImages always returns an amp-img which had fetchpriority=high. Notice also how AMP Optimizer will preserve the loading attribute from the amp-img > noscript > img callback.

[westonruter]

I can see that the first todo item is completed with the spec update in #7615, but it's not yet merged.

[westonruter]

Workaround plugin code to suppress the error:

add_filter(
	'amp_validation_error_sanitized',
	static function ( $sanitized, $error ) {
		if (
			'DISALLOWED_ATTR' === $error['code'] &&
			'fetchpriority' === $error['node_name']
		) {
			$sanitized = true;
		}
		return $sanitized;
	},
	10,
	2
);

[westonruter]

@thelovekesh Just added this todo:

Update amp-toolbox-php to dev-master util changes tested and full 11.3 release is made.

This can be done as part of the PR that makes sure that fetchpriority is preserved on the img when converted to amp-img (or when native img is enabled). Actually I expect it is already passed through, so there may not be any changes other than adding some AMP_Img_Sanitizer tests to verify that the expected behavior is happening.

[thelovekesh]

Yes, only one change is required in AMP_Img_Sanitizer to prevent adding fetchpriority attribute to the amp-img.

[pavanpatil1]

QA Passed ✅

The FetchPriority attribute is visible within the image and remains present when the native HTML image tag is enabled.

Task 1:

The fetchpriority is added inside the image tag -

https://github.com/ampproject/amp-wp/blob/66b86680f6f1db819be2a0b37f5d5dee64cac201/includes/sanitizers/class-amp-allowed-tags-generated.php#L11623C10-L11623C10

Task 2:

Cross-checked it and it is working fine. It is not supported now.

Details

Task 3:

With the native HTML image tag enabled:

Details

With the amp-img tag:

Details

Task 4:

The amp-toolbox-php is updated to dev-mode:

https://github.com/ampproject/amp-wp/blob/66b86680f6f1db819be2a0b37f5d5dee64cac201/composer.json#L17C4-L17C42