Don't prepare the response body for HEAD requests

src/wp-includes/rest-api/class-wp-rest-request.php

@@ -161,6 +161,18 @@ public function get_headers() {
 		return $this->headers;
 	}
 
+	/**
+	 * Determines if the request is the given method.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $method HTTP method.
+	 * @return bool Whether the request is of the given method.
+	 */
+	public function is_method( $method ) {
+		return $this->get_method() === strtoupper( $method );
+	}
+
 	/**
 	 * Canonicalizes the header name.
 	 *

src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php

@@ -305,6 +305,10 @@ public function get_items( $request ) {
 			return $parent;
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this handler doesn't add any response headers.
+			return new WP_REST_Response();
+		}
 		$response  = array();
 		$parent_id = $parent->ID;
 		$revisions = wp_get_post_revisions( $parent_id, array( 'check_enabled' => false ) );
@@ -448,6 +452,11 @@ public function prepare_item_for_response( $item, $request ) {
 		// Restores the more descriptive, specific name for use within this method.
 		$post = $item;
 
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php */
+			return apply_filters( 'rest_prepare_autosave', new WP_REST_Response(), $post, $request );
+		}
 		$response = $this->revisions_controller->prepare_item_for_response( $post, $request );
 		$fields   = $this->get_fields_for_response( $request );
 

src/wp-includes/rest-api/endpoints/class-wp-rest-block-pattern-categories-controller.php

@@ -81,6 +81,11 @@ public function get_items_permissions_check( $request ) {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_items( $request ) {
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this handler doesn't add any response headers.
+			return new WP_REST_Response();
+		}
+
 		$response   = array();
 		$categories = WP_Block_Pattern_Categories_Registry::get_instance()->get_all_registered();
 		foreach ( $categories as $category ) {

src/wp-includes/rest-api/endpoints/class-wp-rest-block-types-controller.php

@@ -131,6 +131,11 @@ public function get_items_permissions_check( $request ) {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_items( $request ) {
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this handler doesn't add any response headers.
+			return new WP_REST_Response();
+		}
+
 		$data        = array();
 		$block_types = $this->block_registry->get_all_registered();
 
@@ -250,6 +255,12 @@ public function prepare_item_for_response( $item, $request ) {
 		// Restores the more descriptive, specific name for use within this method.
 		$block_type = $item;
 
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-block-types-controller.php */
+			return apply_filters( 'rest_prepare_block_type', new WP_REST_Response(), $block_type, $request );
+		}
+
 		$fields = $this->get_fields_for_response( $request );
 		$data   = array();
 

src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php

@@ -262,6 +262,14 @@ public function get_items( $request ) {
 			$prepared_args['offset'] = $prepared_args['number'] * ( absint( $request['page'] ) - 1 );
 		}
 
+		$is_head_request = $request->is_method( 'HEAD' );
+		if ( $is_head_request ) {
+			// Force the 'fields' argument. For HEAD requests, only post IDs are required to calculate pagination.
+			$prepared_args['fields'] = 'ids';
+			// Disable priming comment meta for HEAD requests to improve performance.
+			$prepared_args['update_comment_meta_cache'] = false;
+		}
+
 		/**
 		 * Filters WP_Comment_Query arguments when querying comments via the REST API.
 		 *
@@ -277,15 +285,17 @@ public function get_items( $request ) {
 		$query        = new WP_Comment_Query();
 		$query_result = $query->query( $prepared_args );
 
-		$comments = array();
+		if ( ! $is_head_request ) {
+			$comments = array();
 
-		foreach ( $query_result as $comment ) {
-			if ( ! $this->check_read_permission( $comment, $request ) ) {
-				continue;
-			}
+			foreach ( $query_result as $comment ) {
+				if ( ! $this->check_read_permission( $comment, $request ) ) {
+					continue;
+				}
 
-			$data       = $this->prepare_item_for_response( $comment, $request );
-			$comments[] = $this->prepare_response_for_collection( $data );
+				$data       = $this->prepare_item_for_response( $comment, $request );
+				$comments[] = $this->prepare_response_for_collection( $data );
+			}
 		}
 
 		$total_comments = (int) $query->found_comments;
@@ -303,7 +313,7 @@ public function get_items( $request ) {
 			$max_pages      = (int) ceil( $total_comments / $request['per_page'] );
 		}
 
-		$response = rest_ensure_response( $comments );
+		$response = $is_head_request ? new WP_REST_Response() : rest_ensure_response( $comments );
 		$response->header( 'X-WP-Total', $total_comments );
 		$response->header( 'X-WP-TotalPages', $max_pages );
 
@@ -1041,6 +1051,12 @@ public function prepare_item_for_response( $item, $request ) {
 		// Restores the more descriptive, specific name for use within this method.
 		$comment = $item;
 
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php */
+			return apply_filters( 'rest_prepare_comment', new WP_REST_Response(), $comment, $request );
+		}
+
 		$fields = $this->get_fields_for_response( $request );
 		$data   = array();
 

src/wp-includes/rest-api/endpoints/class-wp-rest-font-collections-controller.php

@@ -89,6 +89,8 @@ public function get_items( $request ) {
 
 		$collections_page = array_slice( $collections_all, ( $page - 1 ) * $per_page, $per_page );
 
+		$is_head_request = $request->is_method( 'HEAD' );
+
 		$items = array();
 		foreach ( $collections_page as $collection ) {
 			$item = $this->prepare_item_for_response( $collection, $request );
@@ -97,11 +99,21 @@ public function get_items( $request ) {
 			if ( is_wp_error( $item ) ) {
 				continue;
 			}
+
+			/*
+			 * Skip preparing the response body for HEAD requests.
+			 * Cannot exit earlier due to backward compatibility reasons,
+			 * as validation occurs in the prepare_item_for_response method.
+			 */
+			if ( $is_head_request ) {
+				continue;
+			}
+
 			$item    = $this->prepare_response_for_collection( $item );
 			$items[] = $item;
 		}
 
-		$response = rest_ensure_response( $items );
+		$response = $is_head_request ? new WP_REST_Response() : rest_ensure_response( $items );
 
 		$response->header( 'X-WP-Total', (int) $total_items );
 		$response->header( 'X-WP-TotalPages', $max_pages );
@@ -175,13 +187,31 @@ public function prepare_item_for_response( $item, $request ) {
 				return $collection_data;
 			}
 
+			/**
+			 * Don't prepare the response body for HEAD requests.
+			 * Can't exit at the beginning of the method due to the potential need to return a WP_Error object.
+			 */
+			if ( $request->is_method( 'HEAD' ) ) {
+				/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-font-collections-controller.php */
+				return apply_filters( 'rest_prepare_font_collection', new WP_REST_Response(), $item, $request );
+			}
+
 			foreach ( $data_fields as $field ) {
 				if ( rest_is_field_included( $field, $fields ) ) {
 					$data[ $field ] = $collection_data[ $field ];
 				}
 			}
 		}
 
+		/**
+		 * Don't prepare the response body for HEAD requests.
+		 * Can't exit at the beginning of the method due to the potential need to return a WP_Error object.
+		 */
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-font-collections-controller.php */
+			return apply_filters( 'rest_prepare_font_collection', new WP_REST_Response(), $item, $request );
+		}
+
 		$response = rest_ensure_response( $data );
 
 		if ( rest_is_field_included( '_links', $fields ) ) {

src/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php

@@ -163,6 +163,8 @@ public function get_items( $request ) {
 			return $global_styles_config;
 		}
 
+		$is_head_request = $request->is_method( 'HEAD' );
+
 		if ( wp_revisions_enabled( $parent ) ) {
 			$registered = $this->get_collection_params();
 			$query_args = array(
@@ -186,6 +188,14 @@ public function get_items( $request ) {
 				}
 			}
 
+			if ( $is_head_request ) {
+				// Force the 'fields' argument. For HEAD requests, only post IDs are required to calculate pagination.
+				$query_args['fields'] = 'ids';
+				// Disable priming post meta for HEAD requests to improve performance.
+				$query_args['update_post_term_cache'] = false;
+				$query_args['update_post_meta_cache'] = false;
+			}
+
 			$revisions_query = new WP_Query();
 			$revisions       = $revisions_query->query( $query_args );
 			$offset          = isset( $query_args['offset'] ) ? (int) $query_args['offset'] : 0;
@@ -228,14 +238,18 @@ public function get_items( $request ) {
 			$page            = (int) $request['page'];
 		}
 
-		$response = array();
+		if ( ! $is_head_request ) {
+			$response = array();
 
-		foreach ( $revisions as $revision ) {
-			$data       = $this->prepare_item_for_response( $revision, $request );
-			$response[] = $this->prepare_response_for_collection( $data );
-		}
+			foreach ( $revisions as $revision ) {
+				$data       = $this->prepare_item_for_response( $revision, $request );
+				$response[] = $this->prepare_response_for_collection( $data );
+			}
 
-		$response = rest_ensure_response( $response );
+			$response = rest_ensure_response( $response );
+		} else {
+			$response = new WP_REST_Response();
+		}
 
 		$response->header( 'X-WP-Total', (int) $total_revisions );
 		$response->header( 'X-WP-TotalPages', (int) $max_pages );
@@ -275,6 +289,11 @@ public function get_items( $request ) {
 	 * @return WP_REST_Response|WP_Error Response object.
 	 */
 	public function prepare_item_for_response( $post, $request ) {
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			return new WP_REST_Response();
+		}
+
 		$parent               = $this->get_parent( $request['parent'] );
 		$global_styles_config = $this->get_decoded_global_styles_json( $post->post_content );
 

src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php

@@ -161,6 +161,11 @@ public function get_items( $request ) {
 			return $raw_patterns;
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this handler doesn't add any response headers.
+			return new WP_REST_Response();
+		}
+
 		$response = array();
 
 		if ( $raw_patterns ) {

src/wp-includes/rest-api/endpoints/class-wp-rest-post-types-controller.php

@@ -109,6 +109,11 @@ public function get_items_permissions_check( $request ) {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_items( $request ) {
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this handler doesn't add any response headers.
+			return new WP_REST_Response();
+		}
+
 		$data  = array();
 		$types = get_post_types( array( 'show_in_rest' => true ), 'objects' );
 
@@ -178,6 +183,12 @@ public function prepare_item_for_response( $item, $request ) {
 		// Restores the more descriptive, specific name for use within this method.
 		$post_type = $item;
 
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-post-types-controller.php */
+			return apply_filters( 'rest_prepare_post_type', new WP_REST_Response(), $post_type, $request );
+		}
+
 		$taxonomies = wp_list_filter( get_object_taxonomies( $post_type->name, 'objects' ), array( 'show_in_rest' => true ) );
 		$taxonomies = wp_list_pluck( $taxonomies, 'name' );
 		$base       = ! empty( $post_type->rest_base ) ? $post_type->rest_base : $post_type->name;

src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -402,6 +402,15 @@ static function ( $format ) {
 		// Force the post_type argument, since it's not a user input variable.
 		$args['post_type'] = $this->post_type;
 
+		$is_head_request = $request->is_method( 'HEAD' );
+		if ( $is_head_request ) {
+			// Force the 'fields' argument. For HEAD requests, only post IDs are required to calculate pagination.
+			$args['fields'] = 'ids';
+			// Disable priming post meta for HEAD requests to improve performance.
+			$args['update_post_term_cache'] = false;
+			$args['update_post_meta_cache'] = false;
+		}
+
 		/**
 		 * Filters WP_Query arguments when querying posts via the REST API.
 		 *
@@ -434,22 +443,24 @@ static function ( $format ) {
 			add_filter( 'post_password_required', array( $this, 'check_password_required' ), 10, 2 );
 		}
 
-		$posts = array();
-
-		update_post_author_caches( $query_result );
-		update_post_parent_caches( $query_result );
+		if ( ! $is_head_request ) {
+			$posts = array();
 
-		if ( post_type_supports( $this->post_type, 'thumbnail' ) ) {
-			update_post_thumbnail_cache( $posts_query );
-		}
+			update_post_author_caches( $query_result );
+			update_post_parent_caches( $query_result );
 
-		foreach ( $query_result as $post ) {
-			if ( ! $this->check_read_permission( $post ) ) {
-				continue;
+			if ( post_type_supports( $this->post_type, 'thumbnail' ) ) {
+				update_post_thumbnail_cache( $posts_query );
 			}
 
-			$data    = $this->prepare_item_for_response( $post, $request );
-			$posts[] = $this->prepare_response_for_collection( $data );
+			foreach ( $query_result as $post ) {
+				if ( ! $this->check_read_permission( $post ) ) {
+					continue;
+				}
+
+				$data    = $this->prepare_item_for_response( $post, $request );
+				$posts[] = $this->prepare_response_for_collection( $data );
+			}
 		}
 
 		// Reset filter.
@@ -479,7 +490,7 @@ static function ( $format ) {
 			);
 		}
 
-		$response = rest_ensure_response( $posts );
+		$response = $is_head_request ? new WP_REST_Response() : rest_ensure_response( $posts );
 
 		$response->header( 'X-WP-Total', (int) $total_posts );
 		$response->header( 'X-WP-TotalPages', (int) $max_pages );
@@ -1824,6 +1835,12 @@ public function prepare_item_for_response( $item, $request ) {
 
 		setup_postdata( $post );
 
+		// Don't prepare the response body for HEAD requests.
+		if ( $request->is_method( 'HEAD' ) ) {
+			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php */
+			return apply_filters( "rest_prepare_{$this->post_type}", new WP_REST_Response(), $post, $request );
+		}
+
 		$fields = $this->get_fields_for_response( $request );
 
 		// Base fields for every post.