REST API: Exempt animated GIF video companions from sideload dimension validation

[adamsilverstein]

Trac ticket: https://core.trac.wordpress.org/ticket/65549

What

Fixes the PHPUnit failure on trunk introduced by the combination of [62619] and [62623]:

1) WP_Test_REST_Attachments_Controller::test_sideload_animated_video_companions_write_metadata
Sideloading animated_video should succeed.
Failed asserting that 400 is identical to 200.

Failing run: https://github.com/WordPress/wordpress-develop/actions/runs/28562019769/attempts/2

Why the failure only appeared on trunk

This is a semantic conflict between two individually green commits:

• [62619] (#64798) added dimension validation to the sideload endpoint: every scalar image_size other than _source_original is now checked against wp_get_registered_image_subsizes() and rejected with rest_upload_unknown_size (400) when not registered.
• [62623] (#65549, PR Media: Add animated GIF to video sideload sizes and companion-file cleanup (backport GB #78410) #12005) added the animated_video / animated_video_poster companion sizes. The PR branch last merged trunk at 19:11 UTC on July 1, before [62619] landed at 21:32 UTC, so its CI ran against a trunk without dimension validation and passed.

Once both were on trunk, sideloading a companion hit the new validation: animated_video is not a registered sub-size, so the request returns 400.

Beyond the test, the real feature flow was broken too: the actual companion is an MP4/WebM video, and wp_getimagesize() cannot read it, which would fail with rest_upload_invalid_image even before the unknown-size check.

Fix

In sideload_item(), skip the wp_getimagesize() read and all dimension checks for the animated_video companion (like the existing _source_original exemption), since a video is not image-readable. The animated_video_poster companion is a real image, so it keeps the readability and positive-dimension checks; validate_image_dimensions() skips only the registered-size constraint for it.

Testing

• tests/phpunit/tests/rest-api/rest-attachments-controller.php --filter test_sideload_animated_video_companions_write_metadata passes.
• The full restattachments group passes locally.

Parity with Gutenberg

The exemption semantics match the Gutenberg polyfill in GB PR #79603 (Gutenberg_REST_Attachments_Controller):

• animated_video (MP4/WebM) and _source_original: skip the wp_getimagesize() read and all dimension checks - the file may not be image-readable at all.
• animated_video_poster: still read via wp_getimagesize() and rejected if unreadable (it is a real image); only the registered-size constraint is skipped.

Commit message

Media: Fix sideload validation for animated GIF video companions.

Update the dimension validation introduced in [62619] so sideloading the `animated_video` and `animated_video_poster` companion sizes added in [62623] work as expected.  

Follow-up to [62619], [62623].

Props mukesh27.
See #65549, #64798.

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Props adamsilverstein.

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Pull request overview

This pull request updates the REST API media sideload flow to accommodate animated GIF “video companion” uploads by exempting the animated_video companion (MP4/WebM) from image-dimension reading/validation, while still allowing the animated_video_poster companion (a real image) to be dimension-read and checked for positive dimensions but not constrained to a registered sub-size.

Changes:

• Skip wp_getimagesize() and all dimension validation for image_size=animated_video in sideload_item().
• Exempt animated_video_poster from the “must be a registered image sub-size” constraint in validate_image_dimensions().

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[mukeshpanchal27]

Committed at https://core.trac.wordpress.org/changeset/62628