[wp-trac] [WordPress Trac] #33054: Better featured image/attachment sanity checks

[WordPress Trac]

#33054: Better featured image/attachment sanity checks
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 Reporter:  ShawnLunny   |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Media        |    Version:  4.2.2
 Severity:  normal       |   Keywords:
  Focuses:               |
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 Use case:

 Add a post: If a user uploads a featured image and the file fails to write
 to disk, the post record contains the url to the image but of course the
 image is broken. The end state is one where the featured image is simply
 broken, but the post record references the image.

 Possible solutions:
 1. Do an extra sanity check after write to disk that the image was
 actually created. If there was a failure alert the user. This is probably
 the easiest.

 2. Or reverse the order of operations, making it transactional in nature.
 That is, create the image(s) first, check if successful, and then update
 the post record. If there is a failure show an alert to the page, and
 don't write the image path to the post record as the file doesn't exist.
 It is alot cleaner to not have an image than having a broken one. It is
 also better if the image was successfully written to disk but the post url
 failed to update for some reason; we can always re choose from the media
 library.

 a. Going above and beyond, the sanity check would keep track of thumbnail
 sizes to be created and make sure they all were successful. If not, don't
 update the post record and remove the thumbnail sizes that did write to
 disk. Once again treat as a transaction; all or nothing.


 Extended impact:
 Many folks use image compression plugins or tools that compress the images
 before writing to disk. Currently if those items fail usually by timeout
 you are left with a broken image and the url is in the meta.

 I propose that there be a pre-check as to the thumbnails to be created
 before the image write even occurs (add a new action hook that keeps track
 of the thumbnails we expect from add_image_size) and then check on the
 backside to make sure we have the image(s) we expect. After that all
 sanity check rules proposed above would apply.

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Ticket URL: <https://core.trac.wordpress.org/ticket/33054>
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