[wp-trac] [WordPress Trac] #53668: Generated images for one file can be overwritten by another with the same name when mapping mime types for generated images

[WordPress Trac]

#53668: Generated images for one file can be overwritten by another with the same
name when mapping mime types for generated images
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 Reporter:  ianmjones                               |       Owner:  (none)
     Type:  defect (bug)                            |      Status:  new
 Priority:  normal                                  |   Milestone:  5.8.1
Component:  Media                                   |     Version:  5.8
 Severity:  normal                                  |  Resolution:
 Keywords:  has-patch needs-testing has-unit-tests  |     Focuses:
----------------------------------------------------+---------------------

Comment (by azaozz):

 Replying to [comment:26 ianmjones]:
 > Replying to [comment:25 azaozz]:
 > > For example: existing files like img.jpg, img-1.png, img-2.webp,
 img-3.png and converting PNG and JPEG to WebP, and uploading img.jpg
 again. Then the sub-sizes of img-3.png will be overwritten if the alt name
 with .png extension is checked before the alt name with .webp (I'll try to
 make another test for this edge case).
 >
 > As mentioned in your PR, I don't think my patch has the problem you
 mention here with regards to skipped png version, recursion saves the day!
 😉️

 The logic there is that for each increase of `$number` all possible
 filenames have to be checked. Doing that with recursion means it has to
 "re-start" each time a possible name clash is detected.

 Then if the conversion settings are like:
 {{{
 Array(
     'image/png' => 'image/webp',
     'image/jpeg' => 'image/webp',
     'image/gif' => 'image/webp',
 )
 }}}

 it will have to check 4 name variations for each `$number` increase. This
 potentially can result in running `wp_unique_filename()` including the two
 filters and `scandir()` 10-15 times. It's definitely going to be quite
 slow :)

 Also firing `wp_unique_filename` filter 10-15 times mostly for filenames
 that will never be used seems like a regression. Perhaps we can pass the
 alt filenames as another argument there, or maybe only the expected
 filename after the image conversion.

 > I see your point about the code you mentioned though. If uploading a new
 series of photos (pic-1.png, pic-2.png, pic-3.png) and the second
 "pic-2.png" clashes with "pic-2.jpg", what do you do?
 >
 > a) pic-1.png, pic-2-1.png, pic-3.png
 > b) pic-1.png, pic-3.png, pic-4.png
 >
 > I take it (a) is expected?

 Yep, as `pic-2` is the original name that WP shouldn't change.

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Ticket URL: <https://core.trac.wordpress.org/ticket/53668#comment:27>
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