[wp-trac] [WordPress Trac] #64677: Client-Side Media: Move `image_editor_output_format` filtering to the upload response

[WordPress Trac]

#64677: Client-Side Media: Move `image_editor_output_format` filtering to the
upload response
-----------------------------+-------------------------
 Reporter:  adamsilverstein  |      Owner:  (none)
     Type:  defect (bug)     |     Status:  new
 Priority:  normal           |  Milestone:  7.0
Component:  Media            |    Version:  trunk
 Severity:  normal           |   Keywords:  needs-patch
  Focuses:                   |
-----------------------------+-------------------------
 In [https://github.com/WordPress/wordpress-develop/pull/10868 #10868]
 (Editor: PHP backports for Client Side Media), the
 `image_editor_output_format` filter is currently applied in the REST API
 index (`get_index`) by iterating over a list of possible input MIME types
 with an empty `$output_formats` array and no `$filename` parameter. As
 noted in [https://github.com/WordPress/wordpress-
 develop/pull/10868#discussion_r2831587138 this review comment], this
 doesn't match how `wp_get_image_editor_output_format()` normally applies
 the filter — it passes the actual filename and a pre-populated default
 mapping.

 == Problem ==

 The current approach:
 * Passes an empty array as the default value instead of the normal default
 mapping
 * Does not supply a `$filename` parameter to the filter
 * Re-filters the same `$output_formats` variable across iterations,
 accumulating results in a way that doesn't match the server-side behavior
 * Is applied generically rather than per-upload, so plugins can't make
 decisions based on the actual input file

 == Proposed Solution ==

 Move the `image_editor_output_format` logic from the REST API index
 response into the '''initial image upload response'''. This is already the
 pattern used for EXIF rotation data in client-side media processing.

 Benefits:
 * The actual input filename and MIME type will be available, so the filter
 operates just like it does on the server side
 * Plugins that hook into `image_editor_output_format` will receive
 meaningful parameters
 * Keeps per-file processing logic in the upload response where it belongs

 == References ==

 * PR: [https://github.com/WordPress/wordpress-develop/pull/10868 #10868]
 * Review: [https://github.com/WordPress/wordpress-
 develop/pull/10868#discussion_r2831587138 @westonruter's comment]
 * Response: [https://github.com/WordPress/wordpress-
 develop/pull/10868#discussion_r2832131664 @adamsilverstein's response]

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Ticket URL: <https://core.trac.wordpress.org/ticket/64677>
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