[wp-trac] [WordPress Trac] #56043: WordPress core Lazy Loading filters don't work on featured images

[WordPress Trac]

#56043: WordPress core Lazy Loading filters don't work on featured images
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 Reporter:  culturalistpress  |       Owner:  (none)
     Type:  defect (bug)      |      Status:  closed
 Priority:  normal            |   Milestone:
Component:  Media             |     Version:  6.0
 Severity:  normal            |  Resolution:  duplicate
 Keywords:                    |     Focuses:  performance
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Comment (by gilbertococchi):

 I was able to reproduce this issue on some WordPress Themes.

 My understanding is that when Themes use the_post_thumbnail method then
 the post-thumbnail-template.php class uses the
 [wp_get_attachment_image](https://github.com/WordPress/WordPress/blob/1cd42e3cbe7890a891d7a37b6a7467188b3ef59e
 /wp-includes/post-thumbnail-template.php#L202) method that is not handled
 well by the
 [wp_get_loading_attr_default](https://github.com/WordPress/WordPress/blob/b90c2adb7f65b610c84db80fa35b66cc036e1a66
 /wp-includes/media.php#L5495-L5516) method.

 I guess it may be feasible to increase the match on detecting Featured
 images by handling this case by not applying loading=lazy on the first
 iteration of the context wp_get_attachment_image.

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Ticket URL: <https://core.trac.wordpress.org/ticket/56043#comment:5>
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