From 7948dbf0c11182a86e690ffeea7df7230129fd15 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Thu, 15 Feb 2018 14:28:13 +0000
Subject: [PATCH] Database: If both `WP_DEBUG` and `WP_DEBUG_DISPLAY` are true,
 display a more specific error message in `wpdb::bail()`.

Props sivel, Mte90, SergeyBiryukov.
Fixes #13657.

git-svn-id: https://develop.svn.wordpress.org/trunk@42716 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/wp-db.php | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index 1e5fda6743..901cf10bac 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -3316,15 +3316,37 @@ class wpdb {
 	 * @return false|void
 	 */
 	public function bail( $message, $error_code = '500' ) {
-		if ( ! $this->show_errors ) {
+		if ( $this->show_errors ) {
+			$error = '';
+
+			if ( $this->use_mysqli ) {
+				if ( $this->dbh instanceof mysqli ) {
+					$error = mysqli_error( $this->dbh );
+				} elseif ( mysqli_connect_errno() ) {
+					$error = mysqli_connect_error();
+				}
+			} else {
+				if ( is_resource( $this->dbh ) ) {
+					$error = mysql_error( $this->dbh );
+				} else {
+					$error = mysql_error();
+				}
+			}
+
+			if ( $error ) {
+				$message = '<p><code>' . $error . "</code></p>\n" . $message;
+			}
+
+			wp_die( $message );
+		} else {
 			if ( class_exists( 'WP_Error', false ) ) {
 				$this->error = new WP_Error( $error_code, $message );
 			} else {
 				$this->error = $message;
 			}
+
 			return false;
 		}
-		wp_die( $message );
 	}