Script Loader: Load the modules to the footer in classic themes

Incremental import maps fail if the import map is printed after the module scripts.
This means, we should always render import maps first. This means that for classic themes, we need to move the import map and modules to the footer because we can't know before that which modules are needed.

Props luisherranz, cbravobernal.
Fixes #60240.
Built from https://develop.svn.wordpress.org/trunk@57345


git-svn-id: https://core.svn.wordpress.org/trunk@56851 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: youknowriad

wp-includes/class-wp-script-modules.php

@@ -89,15 +89,12 @@ public function register( string $id, string $src, array $deps = array(), $versi
 				'version'      => $version,
 				'enqueue'      => isset( $this->enqueued_before_registered[ $id ] ),
 				'dependencies' => $dependencies,
-				'enqueued'     => false,
-				'preloaded'    => false,
 			);
 		}
 	}
 
 	/**
-	 * Marks the script module to be enqueued in the page the next time
-	 * `print_enqueued_script_modules` is called.
+	 * Marks the script module to be enqueued in the page.
 	 *
 	 * If a src is provided and the script module has not been registered yet, it
 	 * will be registered.
@@ -158,74 +155,49 @@ public function dequeue( string $id ) {
 	 * Adds the hooks to print the import map, enqueued script modules and script
 	 * module preloads.
 	 *
-	 * It adds the actions to print the enqueued script modules and script module
-	 * preloads to both `wp_head` and `wp_footer` because in classic themes, the
-	 * script modules used by the theme and plugins will likely be able to be
-	 * printed in the `head`, but the ones used by the blocks will need to be
-	 * enqueued in the `footer`.
-	 *
-	 * As all script modules are deferred and dependencies are handled by the
-	 * browser, the order of the script modules is not important, but it's still
-	 * better to print the ones that are available when the `wp_head` is rendered,
-	 * so the browser starts downloading those as soon as possible.
-	 *
-	 * The import map is also printed in the footer to be able to include the
-	 * dependencies of all the script modules, including the ones printed in the
+	 * In classic themes, the script modules used by the blocks are not yet known
+	 * when the `wp_head` actions is fired, so it needs to print everything in the
 	 * footer.
 	 *
 	 * @since 6.5.0
 	 */
 	public function add_hooks() {
-		add_action( 'wp_head', array( $this, 'print_enqueued_script_modules' ) );
-		add_action( 'wp_head', array( $this, 'print_script_module_preloads' ) );
-		add_action( 'wp_footer', array( $this, 'print_enqueued_script_modules' ) );
-		add_action( 'wp_footer', array( $this, 'print_script_module_preloads' ) );
-		add_action( 'wp_footer', array( $this, 'print_import_map' ) );
+		$position = wp_is_block_theme() ? 'wp_head' : 'wp_footer';
+		add_action( $position, array( $this, 'print_import_map' ) );
+		add_action( $position, array( $this, 'print_enqueued_script_modules' ) );
+		add_action( $position, array( $this, 'print_script_module_preloads' ) );
 	}
 
 	/**
 	 * Prints the enqueued script modules using script tags with type="module"
 	 * attributes.
 	 *
-	 * If a enqueued script module has already been printed, it will not be
-	 * printed again on subsequent calls to this function.
-	 *
 	 * @since 6.5.0
 	 */
 	public function print_enqueued_script_modules() {
 		foreach ( $this->get_marked_for_enqueue() as $id => $script_module ) {
-			if ( false === $script_module['enqueued'] ) {
-				// Mark it as enqueued so it doesn't get enqueued again.
-				$this->registered[ $id ]['enqueued'] = true;
-
-				wp_print_script_tag(
-					array(
-						'type' => 'module',
-						'src'  => $this->get_versioned_src( $script_module ),
-						'id'   => $id . '-js-module',
-					)
-				);
-			}
+			wp_print_script_tag(
+				array(
+					'type' => 'module',
+					'src'  => $this->get_versioned_src( $script_module ),
+					'id'   => $id . '-js-module',
+				)
+			);
 		}
 	}
 
 	/**
 	 * Prints the the static dependencies of the enqueued script modules using
 	 * link tags with rel="modulepreload" attributes.
 	 *
-	 * If a script module is marked for enqueue, it will not be preloaded. If a
-	 * preloaded script module has already been printed, it will not be printed
-	 * again on subsequent calls to this function.
+	 * If a script module is marked for enqueue, it will not be preloaded.
 	 *
 	 * @since 6.5.0
 	 */
 	public function print_script_module_preloads() {
 		foreach ( $this->get_dependencies( array_keys( $this->get_marked_for_enqueue() ), array( 'static' ) ) as $id => $script_module ) {
-			// Don't preload if it's marked for enqueue or has already been preloaded.
-			if ( true !== $script_module['enqueue'] && false === $script_module['preloaded'] ) {
-				// Mark it as preloaded so it doesn't get preloaded again.
-				$this->registered[ $id ]['preloaded'] = true;
-
+			// Don't preload if it's marked for enqueue.
+			if ( true !== $script_module['enqueue'] ) {
 				echo sprintf(
 					'<link rel="modulepreload" href="%s" id="%s">',
 					esc_url( $this->get_versioned_src( $script_module ) ),

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-alpha-57344';
+$wp_version = '6.5-alpha-57345';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.