wp-block-post-featured-image missing the lazy attribute

[Mte90]

Description

Since WP 5.5 the lazy attribute to img tags is added automatically.

Well this block doesn't have that value...

gutenberg/packages/block-library/src/post-featured-image/edit.js

Line 152 in ba9b739

image = (

Step-by-step reproduction instructions

1. Add that block and see the html generated

Screenshots, screen recording, code snippet

No response

Environment info

• WP 6.0

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[aristath]

I remember seeing a discussion somewhere that featured-images should not get the lazy attribute, because usually they are above the fold, and lazy-loading them is bad for performance and the user-experience... 🤔
I can see a post on make that says the 1st image won't be lazy-loaded, could that be what's happening here? https://make.wordpress.org/core/2021/12/29/enhanced-lazy-loading-performance-in-5-9/

[Mte90]

I remember that discussion but when in a page there is more then one?

[aristath]

but when in a page there is more then one?

An example would be an archive of posts, where each post has its featured image inside the query loop 😉

[ockham]

Potentially related Trac ticket: https://core.trac.wordpress.org/ticket/56930.

[spacedmonkey]

Related: #45224

[felixarntz]

@Mte90 @aristath @ockham @spacedmonkey https://core.trac.wordpress.org/ticket/56930 is primarily caused by https://core.trac.wordpress.org/ticket/55996, which is also covered in #45224 and now has a working (core) PR in WordPress/wordpress-develop#3549.

The problem here is a different one though: I'm unsure whether the original issue description is accurate - the loading="lazy" attribute is expected to not be present if the featured image appears on top of the page (specifically, the very first image that is either a featured image or part of any post content blob), while it is expected to be present on the featured image otherwise. I just tested this with the WordPress/wordpress-develop#3549 PR branch, that fixes the root problem around lazy-loading attriibutes being incorrectly applied in block themes, and with Twenty Twenty-Two: In a post where I have the featured image as the first image on the page, it still receives the loading="lazy" attribute - so that is incorrect, but it's still the opposite of what the issue description here says the problem would be.

I believe there is something we need to tweak in the core/post-featured-image block PHP implementation so that the core heuristics for whether the attribute should be added applies correctly. Will look into it.

[felixarntz]

I found the problem here and addressed it as part of WordPress/wordpress-develop#3560: Basically, the issue with the core/post-featured-image block here is the lack of https://github.com/WordPress/wordpress-develop/pull/3560/files#diff-a9372558b4bbc50ffb4ff3b685da5c4e1ed1e2d58cf97e47c0abbfd7c58681c9R24 in that block rendering function. This is currently breaking backward compatibility (and this core feature!); the fix here is exactly the same that has already been added to the core/post-content block for the same reason.

[felixarntz]

Fixed via #45534.

To follow the wider-reaching WP core fix, please follow along https://core.trac.wordpress.org/ticket/56930.