View Transitions: Ensure animation duration defaults to 1000ms when i…

[sonali195]

Summary

In the View Transitions plugin, the plvt_inject_animation_duration() docblock explicitly states:

@param int $animation_duration Transition duration in milliseconds. Will be converted to seconds. Defaults to 1000ms if invalid.

However, the function was calculating $seconds = $animation_duration / 1000; directly without verifying whether $animation_duration <= 0. If an invalid or zero duration was passed, it would generate a 0s or negative duration rule in CSS instead of defaulting to the documented 1000ms.

This pull request:

1. Implements the fallback in plvt_inject_animation_duration() so that any duration <= 0 defaults to 1000ms.
2. Adds comprehensive PHPUnit test coverage for plvt_inject_animation_duration(), plvt_sanitize_view_transitions_theme_support(), and plvt_register_view_transition_animations().

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• Unit tests

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation: No.
• I have updated the documentation accordingly: N/A.
• I have added tests to cover my changes.
• All new and existing tests passed.

[github-actions]

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Co-authored-by: sonali195 <sonaliprajapati@git.wordpress.org>
Co-authored-by: adamsilverstein <adamsilverstein@git.wordpress.org>

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[adamsilverstein]

This is called with abs_int in https://github.com/WordPress/performance/pull/2706/changes#diff-1c421c546ad4335a5b5233d0dbb71cd84a39fb2049233e0b0e96241e0e58288aR319, but a guard may still be worthwhile in case others call the function incorrectly.

Wouldn't 0 be a valid value here?

The docblock seems inaccurate, the default is supposed to be 400 ms (settings.php:69), maybe we should fix that as well?

[sonali195]

Thanks for the great feedback! You are completely right on all points:

1. Allow 0ms as valid duration: Updated the check to strictly negative ($animation_duration < 0). A value of 0 is preserved and renders 0s, which is valid CSS for instant transitions.
2. Default to 400ms & docblock fix: Updated the docblock and fallback value to 400ms to stay consistent with settings.php and theme.php (as updated in Set default view transition duration to 400 for better alignment with browser default #2081).
3. Test coverage: Updated the unit test suite to verify that 0ms produces 0s, and negative values default to 400ms (0.4s). Also fixed the array index offset in the theme support unit test.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.54%. Comparing base (a25f804) to head (540824a).
⚠️ Report is 2 commits behind head on trunk.

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #2706      +/-   ##
==========================================
+ Coverage   70.50%   71.54%   +1.03%     
==========================================
  Files          91       91              
  Lines        7869     7871       +2     
==========================================
+ Hits         5548     5631      +83     
+ Misses       2321     2240      -81     

Flag	Coverage Δ
multisite	71.54% <100.00%> (+1.03%)	⬆️
single	35.77% <100.00%> (+0.43%)	⬆️

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[sonali195]

Thanks for the great feedback! You are completely right on all points:

1. Allow 0ms as valid duration: Updated the check to strictly negative ($animation_duration < 0). A value of 0 is preserved and renders 0s, which is valid CSS for instant transitions.
2. Default to 400ms & docblock fix: Updated the docblock and fallback value to 400ms to stay consistent with settings.php and theme.php (as updated in Set default view transition duration to 400 for better alignment with browser default #2081).
3. Test coverage: Updated the unit test suite to verify that 0ms produces 0s, and negative values default to 400ms (0.4s). Also fixed the array index offset in the theme support unit test.

(Could a maintainer also please add the [Type] Bug and no milestone labels so the PR validation checks pass? Thank you!)