Script Loader: Refactor Etag generation for concatenated assets.

Move Etag HTTP header generation in `load-scripts.php` and `load-styles.php` to `WP_Dependencies`.

Introduces the method `WP_Dependencies::get_etag()` and associated unit tests.

Follow up to [57943].

Props vrajadas, martinkrcho, mukesh27.
Fixes #61485.


git-svn-id: https://develop.svn.wordpress.org/trunk@58935 602fd350-edb4-49c9-b593-d223f7449a82

Author: peterwilsoncc

src/wp-admin/load-scripts.php

@@ -52,24 +52,7 @@
 wp_default_packages_vendor( $wp_scripts );
 wp_default_packages_scripts( $wp_scripts );
 
-$etag = "WP:{$wp_version};";
-
-foreach ( $load as $handle ) {
-	if ( ! array_key_exists( $handle, $wp_scripts->registered ) ) {
-		continue;
-	}
-
-	$ver   = $wp_scripts->registered[ $handle ]->ver ? $wp_scripts->registered[ $handle ]->ver : $wp_version;
-	$etag .= "{$handle}:{$ver};";
-}
-
-/*
- * This is not intended to be cryptographically secure, just a fast way to get
- * a fixed length string based on the script versions. As this file does not
- * load the full WordPress environment, it is not possible to use the salted
- * wp_hash() function.
- */
-$etag = 'W/"' . md5( $etag ) . '"';
+$etag = $wp_scripts->get_etag( $load );
 
 if ( isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) && stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) === $etag ) {
 	header( "$protocol 304 Not Modified" );

src/wp-admin/load-styles.php

@@ -55,24 +55,7 @@
 $wp_styles = new WP_Styles();
 wp_default_styles( $wp_styles );
 
-$etag = "WP:{$wp_version};";
-
-foreach ( $load as $handle ) {
-	if ( ! array_key_exists( $handle, $wp_styles->registered ) ) {
-		continue;
-	}
-
-	$ver   = $wp_styles->registered[ $handle ]->ver ? $wp_styles->registered[ $handle ]->ver : $wp_version;
-	$etag .= "{$handle}:{$ver};";
-}
-
-/*
- * This is not intended to be cryptographically secure, just a fast way to get
- * a fixed length string based on the script versions. As this file does not
- * load the full WordPress environment, it is not possible to use the salted
- * wp_hash() function.
- */
-$etag = 'W/"' . md5( $etag ) . '"';
+$etag = $wp_styles->get_etag( $wp_version, $load );
 
 if ( isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) && stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) === $etag ) {
 	header( "$protocol 304 Not Modified" );

src/wp-includes/class-wp-dependencies.php

@@ -490,4 +490,42 @@ public function set_group( $handle, $recursion, $group ) {
 
 		return true;
 	}
+
+	/**
+	 * Get etag header for cache validation.
+	 *
+	 * @since 6.7.0
+	 *
+	 * @global string $wp_version The WordPress version string.
+	 *
+	 * @param string[] $load Array of script or style handles to load.
+	 * @return string Etag header.
+	 */
+	public function get_etag( $load ) {
+		/*
+		 * Note: wp_get_wp_version() is not used here, as this file can be included
+		 * via wp-admin/load-scripts.php or wp-admin/load-styles.php, in which case
+		 * wp-includes/functions.php is not loaded.
+		 */
+		global $wp_version;
+
+		$etag = "WP:{$wp_version};";
+
+		foreach ( $load as $handle ) {
+			if ( ! array_key_exists( $handle, $this->registered ) ) {
+				continue;
+			}
+
+			$ver   = $this->registered[ $handle ]->ver ?? $wp_version;
+			$etag .= "{$handle}:{$ver};";
+		}
+
+		/*
+		 * This is not intended to be cryptographically secure, just a fast way to get
+		 * a fixed length string based on the script versions. As this file does not
+		 * load the full WordPress environment, it is not possible to use the salted
+		 * wp_hash() function.
+		 */
+		return 'W/"' . md5( $etag ) . '"';
+	}
 }

tests/phpunit/tests/dependencies.php

@@ -148,4 +148,94 @@ public function test_enqueue_before_register() {
 
 		$this->assertContains( 'one', $dep->queue );
 	}
+
+	/**
+	 * Data provider for test_get_etag.
+	 *
+	 * @return array[]
+	 */
+	public function data_provider_get_etag() {
+		return array(
+			'should accept one dependency'              => array(
+				'load'               => array(
+					'abcd' => '1.0.2',
+				),
+				'hash_source_string' => 'WP:6.7;abcd:1.0.2;',
+				'expected'           => 'W/"8145d7e3c41d5a9cc2bccba4afa861fc"',
+			),
+			'should accept empty array of dependencies' => array(
+				'load'               => array(),
+				'hash_source_string' => 'WP:6.7;',
+				'expected'           => 'W/"7ee896c19250a3d174f11469a4ad0b1e"',
+			),
+		);
+	}
+
+	/**
+	 * Tests get_etag method for WP_Scripts.
+	 *
+	 * @ticket 58433
+	 * @ticket 61485
+	 *
+	 * @covers WP_Dependencies::get_etag
+	 *
+	 * @dataProvider data_provider_get_etag
+	 *
+	 * @param array  $load               List of scripts to load.
+	 * @param string $hash_source_string Hash source string.
+	 * @param string $expected           Expected etag.
+	 */
+	public function test_get_etag_scripts( $load, $hash_source_string, $expected ) {
+		global $wp_version;
+		// Modify global to avoid tests needing to change with each new version of WordPress.
+		$original_wp_version = $wp_version;
+		$wp_version          = '6.7';
+		$instance            = wp_scripts();
+
+		foreach ( $load as $handle => $ver ) {
+			// The src should not be empty.
+			wp_enqueue_script( $handle, 'https://example.org', array(), $ver );
+		}
+
+		$result = $instance->get_etag( array_keys( $load ) );
+
+		// Restore global prior to making assertions.
+		$wp_version = $original_wp_version;
+
+		$this->assertSame( $expected, $result, "Expected MD hash: $expected for $hash_source_string, but got: $result." );
+	}
+
+	/**
+	 * Tests get_etag method for WP_Styles.
+	 *
+	 * @ticket 58433
+	 * @ticket 61485
+	 *
+	 * @covers WP_Dependencies::get_etag
+	 *
+	 * @dataProvider data_provider_get_etag
+	 *
+	 * @param array  $load               List of styles to load.
+	 * @param string $hash_source_string Hash source string.
+	 * @param string $expected           Expected etag.
+	 */
+	public function test_get_etag_styles( $load, $hash_source_string, $expected ) {
+		global $wp_version;
+		// Modify global to avoid tests needing to change with each new version of WordPress.
+		$original_wp_version = $wp_version;
+		$wp_version          = '6.7';
+		$instance            = wp_scripts();
+
+		foreach ( $load as $handle => $ver ) {
+			// The src should not be empty.
+			wp_enqueue_style( $handle, 'https://example.cdn', array(), $ver );
+		}
+
+		$result = $instance->get_etag( array_keys( $load ) );
+
+		// Restore global prior to making assertions.
+		$wp_version = $original_wp_version;
+
+		$this->assertSame( $expected, $result, "Expected MD hash: $expected for $hash_source_string, but got: $result." );
+	}
 }