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-comments-controller.php

@@ -262,6 +262,12 @@ 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';
+		}
+
 		/**
 		 * Filters WP_Comment_Query arguments when querying comments via the REST API.
 		 *
@@ -277,15 +283,17 @@ 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 +311,7 @@ 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 );
 
@@ -427,6 +435,11 @@ public function get_item( $request ) {
 			return $comment;
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Don't prepare response body for HEAD requests.
+			return new WP_REST_Response();
+		}
+
 		$data     = $this->prepare_item_for_response( $comment, $request );
 		$response = rest_ensure_response( $data );
 

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

@@ -402,6 +402,12 @@ 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';
+		}
+
 		/**
 		 * Filters WP_Query arguments when querying posts via the REST API.
 		 *
@@ -434,22 +440,24 @@ static function ( $format ) {
 			add_filter( 'post_password_required', array( $this, 'check_password_required' ), 10, 2 );
 		}
 
-		$posts = array();
+		if ( ! $is_head_request ) {
+			$posts = array();
 
-		update_post_author_caches( $query_result );
-		update_post_parent_caches( $query_result );
-
-		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 +487,7 @@ 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 );
@@ -632,8 +640,12 @@ public function get_item( $request ) {
 			return $post;
 		}
 
-		$data     = $this->prepare_item_for_response( $post, $request );
-		$response = rest_ensure_response( $data );
+		if ( $request->is_method( 'HEAD' ) ) {
+			$response = new WP_REST_Response();
+		} else {
+			$data     = $this->prepare_item_for_response( $post, $request );
+			$response = rest_ensure_response( $data );
+		}
 
 		if ( is_post_type_viewable( get_post_type_object( $post->post_type ) ) ) {
 			$response->link_header( 'alternate', get_permalink( $post->ID ), array( 'type' => 'text/html' ) );

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

@@ -114,6 +114,11 @@ public function get_items_permissions_check( $request ) {
 	 */
 	public function get_items( $request ) {
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			// Return early as this method doesn't add any headers.
+			return new WP_REST_Response();
+		}
+
 		// Retrieve the list of registered collection query parameters.
 		$registered = $this->get_collection_params();
 
@@ -191,6 +196,10 @@ public function get_item( $request ) {
 			);
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			return new WP_REST_Response();
+		}
+
 		$data = $this->prepare_item_for_response( $tax_obj, $request );
 
 		return rest_ensure_response( $data );

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

@@ -312,6 +312,12 @@ public function get_items( $request ) {
 			$prepared_args = array_merge( $prepared_args, $taxonomy_obj->args );
 		}
 
+		$is_head_request = $request->is_method( 'HEAD' );
+		if ( $is_head_request ) {
+			// Force the 'fields' argument. For HEAD requests, only term IDs are required.
+			$prepared_args['fields'] = 'ids';
+		}
+
 		/**
 		 * Filters get_terms() arguments when querying terms via the REST API.
 		 *
@@ -354,14 +360,15 @@ public function get_items( $request ) {
 			$total_terms = 0;
 		}
 
-		$response = array();
-
-		foreach ( $query_result as $term ) {
-			$data       = $this->prepare_item_for_response( $term, $request );
-			$response[] = $this->prepare_response_for_collection( $data );
+		if ( ! $is_head_request ) {
+			$response = array();
+			foreach ( $query_result as $term ) {
+				$data       = $this->prepare_item_for_response( $term, $request );
+				$response[] = $this->prepare_response_for_collection( $data );
+			}
 		}
 
-		$response = rest_ensure_response( $response );
+		$response = $is_head_request ? new WP_REST_Response() : rest_ensure_response( $response );
 
 		// Store pagination values for headers.
 		$per_page = (int) $prepared_args['number'];
@@ -468,6 +475,10 @@ public function get_item( $request ) {
 			return $term;
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			return new WP_REST_Response();
+		}
+
 		$response = $this->prepare_item_for_response( $term, $request );
 
 		return rest_ensure_response( $response );

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

@@ -333,6 +333,12 @@ public function get_items( $request ) {
 			}
 			$prepared_args['search'] = '*' . $prepared_args['search'] . '*';
 		}
+
+		$is_head_request = $request->is_method( 'HEAD' );
+		if ( $is_head_request ) {
+			// Force the 'fields' argument. For HEAD requests, only user IDs are required.
+			$prepared_args['fields'] = 'id';
+		}
 		/**
 		 * Filters WP_User_Query arguments when querying users via the REST API.
 		 *
@@ -347,14 +353,16 @@ public function get_items( $request ) {
 
 		$query = new WP_User_Query( $prepared_args );
 
-		$users = array();
+		if ( ! $is_head_request ) {
+			$users = array();
 
-		foreach ( $query->get_results() as $user ) {
-			$data    = $this->prepare_item_for_response( $user, $request );
-			$users[] = $this->prepare_response_for_collection( $data );
+			foreach ( $query->get_results() as $user ) {
+				$data    = $this->prepare_item_for_response( $user, $request );
+				$users[] = $this->prepare_response_for_collection( $data );
+			}
 		}
 
-		$response = rest_ensure_response( $users );
+		$response = $is_head_request ? new WP_REST_Response() : rest_ensure_response( $users );
 
 		// Store pagination values for headers then unset for count query.
 		$per_page = (int) $prepared_args['number'];
@@ -480,6 +488,10 @@ public function get_item( $request ) {
 			return $user;
 		}
 
+		if ( $request->is_method( 'HEAD' ) ) {
+			return new WP_REST_Response();
+		}
+
 		$user     = $this->prepare_item_for_response( $user, $request );
 		$response = rest_ensure_response( $user );