Functions: Memoize wp_normalize_path().

`wp_normalize_path()` is called thousands of times on a given request. This patch adds memoization via a function-local static variable. This reduces the call count to the underlying `wp_is_stream()` function, and measured in testing around a 66% cache hit rate.

In testing, for a site making 4000 calls to `wp_normalize_path()`, this patch led to a reduction in runtime from 1.4 ms to 0.4 ms on the test computer. While small, this time occurs early in the hotpath of the loading WordPress.

Developed in: WordPress#10770
Discussed in: https://core.trac.wordpress.org/ticket/64538

Props dmsnell, josephscott, mreishus, westonruter.
Fixes #64538.


git-svn-id: https://develop.svn.wordpress.org/trunk@61857 602fd350-edb4-49c9-b593-d223f7449a82

Author: dmsnell

src/wp-includes/functions.php

@@ -2179,12 +2179,21 @@ function path_join( $base, $path ) {
  * @since 4.4.0 Ensures upper-case drive letters on Windows systems.
  * @since 4.5.0 Allows for Windows network shares.
  * @since 4.9.7 Allows for PHP file wrappers.
+ * @since 7.0.0 Uses a static cache to store normalized paths.
  *
  * @param string $path Path to normalize.
  * @return string Normalized path.
  */
-function wp_normalize_path( $path ) {
-	$wrapper = '';
+function wp_normalize_path( $path ): string {
+	$path = (string) $path;
+
+	static $cache = array();
+	if ( isset( $cache[ $path ] ) ) {
+		return $cache[ $path ];
+	}
+
+	$original_path = $path;
+	$wrapper       = '';
 
 	if ( wp_is_stream( $path ) ) {
 		list( $wrapper, $path ) = explode( '://', $path, 2 );
@@ -2196,14 +2205,15 @@ function wp_normalize_path( $path ) {
 	$path = str_replace( '\\', '/', $path );
 
 	// Replace multiple slashes down to a singular, allowing for network shares having two slashes.
-	$path = preg_replace( '|(?<=.)/+|', '/', $path );
+	$path = (string) preg_replace( '|(?<=.)/+|', '/', $path );
 
 	// Windows paths should uppercase the drive letter.
 	if ( ':' === substr( $path, 1, 1 ) ) {
 		$path = ucfirst( $path );
 	}
 
-	return $wrapper . $path;
+	$cache[ $original_path ] = $wrapper . $path;
+	return $cache[ $original_path ];
 }
 
 /**

tests/phpunit/tests/functions.php

@@ -222,9 +222,66 @@ public function data_wp_normalize_path() {
 			array( 'php://input', 'php://input' ),
 			array( 'http://example.com//path.ext', 'http://example.com/path.ext' ),
 			array( 'file://c:\\www\\path\\', 'file://C:/www/path/' ),
+
+			// Edge cases.
+			array( '', '' ), // Empty string should return empty string.
+			array( 123, '123' ), // Integer should be cast to string.
 		);
 	}
 
+	/**
+	 * Tests that wp_normalize_path() works with objects that have __toString().
+	 *
+	 * This is important because the function uses a static cache, and the input
+	 * must be cast to string before being used as an array key.
+	 *
+	 * @ticket 64538
+	 */
+	public function test_wp_normalize_path_with_stringable_object() {
+		$file_info = new SplFileInfo( '/var/www/html\\test' );
+
+		$this->assertSame( '/var/www/html/test', wp_normalize_path( $file_info ) );
+	}
+
+	/**
+	 * Tests that wp_normalize_path() returns consistent results on repeated calls.
+	 *
+	 * The function uses a static cache, so this verifies cache behavior.
+	 *
+	 * @ticket 64538
+	 */
+	public function test_wp_normalize_path_returns_consistent_results() {
+		$path = 'C:\\www\\path\\';
+
+		$first_call  = wp_normalize_path( $path );
+		$second_call = wp_normalize_path( $path );
+		$third_call  = wp_normalize_path( $path );
+
+		$this->assertSame( $first_call, $second_call, 'Second call should return same result as first.' );
+		$this->assertSame( $second_call, $third_call, 'Third call should return same result as second.' );
+		$this->assertSame( 'C:/www/path/', $first_call, 'Normalized path should match expected value.' );
+	}
+
+	/**
+	 * Tests that wp_normalize_path() static cache stores results.
+	 *
+	 * @ticket 64538
+	 */
+	public function test_wp_normalize_path_static_cache() {
+		$path     = '/var/www/cache-test\\subdir\\';
+		$expected = '/var/www/cache-test/subdir/';
+
+		$result = wp_normalize_path( $path );
+		$this->assertSame( $expected, $result );
+
+		$reflection  = new ReflectionFunction( 'wp_normalize_path' );
+		$static_vars = $reflection->getStaticVariables();
+
+		$this->assertArrayHasKey( 'cache', $static_vars, 'Static cache array should exist.' );
+		$this->assertArrayHasKey( $path, $static_vars['cache'], 'Cache should contain the normalized path.' );
+		$this->assertSame( $expected, $static_vars['cache'][ $path ], 'Cached value should match the expected normalized path.' );
+	}
+
 	public function test_wp_unique_filename() {
 
 		$testdir = DIR_TESTDATA . '/images/';