Add type checking for expected elapsed time in saved queries

Author: westonruter

plugins/performance-lab/includes/server-timing/defaults.php

@@ -25,7 +25,9 @@
  * @since 1.8.0
  */
 function perflab_register_default_server_timing_before_template_metrics(): void {
-	$calculate_before_template_metrics = static function (): void {
+	$current_function = __FUNCTION__;
+
+	$calculate_before_template_metrics = static function () use ( $current_function ): void {
 		// WordPress execution prior to serving the template.
 		perflab_server_timing_register_metric(
 			'before-template',
@@ -44,17 +46,41 @@ function perflab_register_default_server_timing_before_template_metrics(): void
 			perflab_server_timing_register_metric(
 				'before-template-db-queries',
 				array(
-					'measure_callback' => static function ( $metric ): void {
+					'measure_callback' => static function ( $metric ) use ( $current_function ): void {
 						// This should never happen, but some odd database implementations may be doing it wrong.
 						if ( ! isset( $GLOBALS['wpdb']->queries ) || ! is_array( $GLOBALS['wpdb']->queries ) ) {
 							return;
 						}
 
+						/**
+						 * Query times.
+						 *
+						 * @var float[] $query_times
+						 */
+						$query_times = array();
+						foreach ( $GLOBALS['wpdb']->queries as $query ) {
+							if ( ! is_array( $query ) || ! isset( $query[1] ) || ! is_float( $query[1] ) ) {
+								wp_trigger_error(
+									$current_function,
+									esc_html(
+										sprintf(
+											/* translators: 1: before-template-db-queries, 2: $wpdb->queries */
+											__( 'Unable to compute server timing for "%1$s" because a saved query in %2$s lacks the elapsed time as the second array value.', 'performance-lab' ),
+											'before-template-db-queries',
+											'$wpdb->queries'
+										)
+									)
+								);
+								return;
+							}
+							$query_times[] = $query[1];
+						}
+
 						// Store this value in a global to later subtract it from total query time after template.
 						$GLOBALS['perflab_query_time_before_template'] = array_reduce(
-							$GLOBALS['wpdb']->queries,
-							static function ( $acc, $query ) {
-								return $acc + $query[1];
+							$query_times,
+							static function ( float $acc, float $query_time ): float {
+								return $acc + $query_time;
 							},
 							0.0
 						);