Gutenberg: prepend_to_selector() comparison

bench-prepend-to-selector.php

<?php
/**
 * Benchmark: prepend_to_selector() implementations.
 *
 * Usage: php bench-prepend-to-selector.php
 */

$data = array(
	'single class selector'                                    => array(
		'selector'   => '.inner',
		'to_prepend' => '.wrapper ',
		'expected'   => '.wrapper .inner',
	),
	'single element selector'                                  => array(
		'selector'   => 'p',
		'to_prepend' => '.wrapper ',
		'expected'   => '.wrapper p',
	),
	'single id selector'                                       => array(
		'selector'   => '#main',
		'to_prepend' => '.wrapper ',
		'expected'   => '.wrapper #main',
	),
	'two comma-separated selectors without spaces'             => array(
		'selector'   => 'h1,h2',
		'to_prepend' => '.wrapper ',
		'expected'   => '.wrapper h1,.wrapper h2',
	),
	'three comma-separated selectors without spaces'           => array(
		'selector'   => 'h1,h2,h3',
		'to_prepend' => '.some-class ',
		'expected'   => '.some-class h1,.some-class h2,.some-class h3',
	),
	'comma-separated class selectors without spaces'           => array(
		'selector'   => '.foo,.bar',
		'to_prepend' => '.prefix ',
		'expected'   => '.prefix .foo,.prefix .bar',
	),
	'prepend without trailing space'                           => array(
		'selector'   => '.child',
		'to_prepend' => '.parent',
		'expected'   => '.parent.child',
	),
	'compound selector without trailing space no comma spaces' => array(
		'selector'   => '.a,.b',
		'to_prepend' => '.parent',
		'expected'   => '.parent.a,.parent.b',
	),
	'descendant selector prepended'                            => array(
		'selector'   => '.block .inner',
		'to_prepend' => '.scope ',
		'expected'   => '.scope .block .inner',
	),
	'descendant selectors comma-separated without spaces'      => array(
		'selector'   => '.block .inner,.block .alt',
		'to_prepend' => '.scope ',
		'expected'   => '.scope .block .inner,.scope .block .alt',
	),
	'empty selector'                                           => array(
		'selector'   => '',
		'to_prepend' => '.prefix ',
		'expected'   => '.prefix ',
	),
	'empty prepend'                                            => array(
		'selector'   => '.child',
		'to_prepend' => '',
		'expected'   => '.child',
	),
	'both empty'                                               => array(
		'selector'   => '',
		'to_prepend' => '',
		'expected'   => '',
	),
	'attribute selector'                                       => array(
		'selector'   => '[data-type="example"]',
		'to_prepend' => '.scope ',
		'expected'   => '.scope [data-type="example"]',
	),
	'pseudo-class selector'                                    => array(
		'selector'   => ':where(.is-layout-flex)',
		'to_prepend' => '.editor ',
		'expected'   => '.editor :where(.is-layout-flex)',
	),
	'many comma-separated selectors without spaces'            => array(
		'selector'   => 'h1,h2,h3,h4,h5,h6',
		'to_prepend' => '.content ',
		'expected'   => '.content h1,.content h2,.content h3,.content h4,.content h5,.content h6',
	),
	'real world block element selector'                        => array(
		'selector'   => 'p',
		'to_prepend' => '.wp-block-group ',
		'expected'   => '.wp-block-group p',
	),
	'real world compound block element selectors'              => array(
		'selector'   => 'a,.wp-element-button',
		'to_prepend' => '.wp-block-group ',
		'expected'   => '.wp-block-group a,.wp-block-group .wp-element-button',
	),
	'spaces after commas are preserved'                        => array(
		'selector'   => 'h1, h2, h3',
		'to_prepend' => '.some-class ',
		'expected'   => '.some-class h1,.some-class  h2,.some-class  h3',
	),
	'spaces after commas preserved with class selectors'       => array(
		'selector'   => '.foo, .bar',
		'to_prepend' => '.prefix ',
		'expected'   => '.prefix .foo,.prefix  .bar',
	),
	'mixed whitespace around commas preserved'                 => array(
		'selector'   => '.a ,  .b , .c',
		'to_prepend' => '.pre ',
		'expected'   => '.pre .a ,.pre   .b ,.pre  .c',
	),
);

function prepend_current( string $selector, string $to_prepend ): string {
	if ( ! str_contains( $selector, ',' ) ) {
		return $to_prepend . $selector;
	}
    $new_selectors = array();
    $selectors     = explode( ',', $selector );
    foreach ( $selectors as $sel ) {
        $new_selectors[] = $to_prepend . $sel;
    }
    return implode( ',', $new_selectors );
}

function prepend_new( string $selector, string $to_prepend ): string {
	if ( ! str_contains( $selector, ',' ) ) {
		return $to_prepend . $selector;
	}
	return $to_prepend . str_replace( ',', ',' . $to_prepend, $selector );
}

$loops      = 200;
$case_count = count( $data );

// --- Correctness check ---
$mismatches = 0;
foreach ( $data as $label => $case ) {
	$current_result = prepend_current( $case['selector'], $case['to_prepend'] );
	$new_result     = prepend_new( $case['selector'], $case['to_prepend'] );

	if ( $current_result !== $case['expected'] ) {
		echo "FAIL [current] $label\n";
		echo "  expected: {$case['expected']}\n";
		echo "  got:      $current_result\n";
		++$mismatches;
	}
	if ( $new_result !== $case['expected'] ) {
		echo "FAIL [new]     $label\n";
		echo "  expected: {$case['expected']}\n";
		echo "  got:      $new_result\n";
		++$mismatches;
	}
}

if ( $mismatches > 0 ) {
	echo "\n$mismatches correctness failure(s) - aborting benchmark.\n";
	exit( 1 );
}
echo "All $case_count cases produce identical results.  Running benchmark...\n\n";

// --- Benchmark: current implementation ---
$start = hrtime( true );
for ( $i = 0; $i < $loops; $i++ ) {
	foreach ( $data as $case ) {
		prepend_current( $case['selector'], $case['to_prepend'] );
	}
}
$time_current = hrtime( true ) - $start;

// --- Benchmark: new implementation ---
$start = hrtime( true );
for ( $i = 0; $i < $loops; $i++ ) {
	foreach ( $data as $case ) {
		prepend_new( $case['selector'], $case['to_prepend'] );
	}
}
$time_new = hrtime( true ) - $start;

// --- Results ---
$total_calls = $loops * $case_count;

printf( "Total calls per implementation: %s\n", number_format( $total_calls ) );
printf( "Loops: %d x %d cases\n\n", $loops, $case_count );

$time_current_ms = $time_current / 1e6;
$time_new_ms     = $time_new / 1e6;

printf( "Current : %.4f ms\n", $time_current_ms );
printf( "New     : %.4f ms\n", $time_new_ms );

$diff_ms   = $time_current_ms - $time_new_ms;
$diff_pct  = ( $diff_ms / $time_current_ms ) * 100;
$direction = $diff_ms > 0 ? 'faster' : 'slower';

printf( "\nDifference: %.4f ms  (%.2f%% %s)\n", abs( $diff_ms ), abs( $diff_pct ), $direction );