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Block Supports: Prevent Additional CSS duplication inside Query Loop #12117

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Block Supports: Prevent Additional CSS duplication inside Query Loop #12117

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6f5a040
Block Supports: Prevent Additional CSS duplication inside Query Loop
Anupkankale Jun 8, 2026
54dbace
Block Supports: Improve Additional CSS deduplication logic
Anupkankale Jun 8, 2026
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12 changes: 12 additions & 0 deletions src/wp-includes/block-supports/custom-css.php
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,18 @@ function wp_render_custom_css_support_styles( $parsed_block ) {
* and can override global styles.
*/
wp_register_style( 'wp-block-custom-css', false, array( 'global-styles' ) );

// Skip if already enqueued — prevents duplication inside Query Loop.
global $wp_styles;
$existing_inline_styles = $wp_styles->get_data( 'wp-block-custom-css', 'after' );
if ( is_array( $existing_inline_styles ) ) {
foreach ( $existing_inline_styles as $style ) {
if ( str_contains( $style, $selector ) ) {
return $parsed_block;
}
}
}

wp_add_inline_style( 'wp-block-custom-css', $processed_css );
}

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47 changes: 47 additions & 0 deletions tests/phpunit/tests/block-supports/wpRenderCustomCssSupportStyles.php
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Original file line number Diff line number Diff line change
Expand Up @@ -264,4 +264,51 @@ public function data_does_not_add_class_name() {
),
);
}

/**
* Tests that CSS is not duplicated when the same block renders multiple times (e.g. inside a Query Loop).
*
* @ticket 65268
*
* @covers ::wp_render_custom_css_support_styles
*/
public function test_css_not_duplicated_inside_query_loop() {
$this->test_block_name = 'test/custom-css-query-loop';
register_block_type(
$this->test_block_name,
array(
'api_version' => 3,
'attributes' => array(
'style' => array(
'type' => 'object',
),
),
'supports' => array( 'customCSS' => true ),
)
);

$parsed_block = array(
'blockName' => 'test/custom-css-query-loop',
'attrs' => array(
'style' => array(
'css' => 'color: fuchsia;',
),
),
);

// Simulate the same block rendering 3 times inside a Query Loop.
wp_render_custom_css_support_styles( $parsed_block );
wp_render_custom_css_support_styles( $parsed_block );
wp_render_custom_css_support_styles( $parsed_block );

// Get the inline styles registered for wp-block-custom-css.
global $wp_styles;
$inline_css = $wp_styles->get_data( 'wp-block-custom-css', 'after' );

// CSS should appear only once, not 3 times.
$this->assertIsArray( $inline_css, 'Inline styles should be registered.' );
$combined = implode( '', $inline_css );
$count = substr_count( $combined, 'color: fuchsia' );
$this->assertSame( 1, $count, 'CSS should only be enqueued once even when block renders multiple times.' );
}
}
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