Skip stylesheets with empty href attributes in Site Health audit

[theaminuli]

What:

Skip stylesheet link elements that have empty href attributes during the Enqueued Assets Health Check audit.

Why:

Some themes and plugins (like Mesmerize Companion) intentionally use empty href attributes with data-href attributes as a performance optimization technique to defer CSS loading. These stylesheets are non-render-blocking by design, but were being incorrectly flagged as errors ("A valid URL was not provided") in the Site Health Status, negatively impacting site scores.

How:

Added a check for empty string href values on line 121 in perflab_aea_audit_blocking_assets(). The condition now reads:

if ( ! is_string( $href ) || '' === $href ) {
    continue;
}

This skips stylesheets with href="" from being audited, similar to how async CSS with non-standard media attributes is already excluded.

Files changed:

helper.php

Fixes #2278

[github-actions]

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Co-authored-by: theaminuli <theaminuldev@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.86%. Comparing base (f7846e4) to head (756a8aa).
⚠️ Report is 2 commits behind head on trunk.

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk    #2281   +/-   ##
=======================================
  Coverage   68.86%   68.86%           
=======================================
  Files          90       90           
  Lines        7610     7610           
=======================================
  Hits         5241     5241           
  Misses       2369     2369           

Flag	Coverage Δ
multisite	68.86% <100.00%> (ø)
single	35.47% <0.00%> (ø)

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[westonruter]

Thank you for the PR. Let's also update the unit test to add an assertion for this change.

[theaminuli]

Test Added

I've added test coverage for the empty href attribute fix in the test_perflab_aea_audit_enqueued_styles() test method.

What the test does:

• Enqueues a stylesheet with style-empty-href handle
• Verifies that this stylesheet is properly skipped from the audit and doesn't appear in the results

Test assertion:

$empty_href_style = array_filter(
	$assets['styles'],
	static function ( $item ) {
		return 'https://empty-href-style.com' === $item['src'];
	}
);
$this->assertEmpty( $empty_href_style );

This ensures that themes/plugins using performance optimization techniques with href="" won't trigger false positives in Site Health checks.

Thanks to @westonruter for the valuable feedback on implementing this test case!

Files changed:

test-audit-enqueued-assets.php