From e50b9c943fddf781f980bba78d1ce927a5dc11b4 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Thu, 15 Feb 2018 14:29:30 +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.
Built from https://develop.svn.wordpress.org/trunk@42716


git-svn-id: http://core.svn.wordpress.org/trunk@42544 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/version.php |  2 +-
 wp-includes/wp-db.php   | 26 ++++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/wp-includes/version.php b/wp-includes/version.php
index b9362fb329..b4f17c1a41 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42715';
+$wp_version = '5.0-alpha-42716';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-includes/wp-db.php b/wp-includes/wp-db.php
index 1e5fda6743..901cf10bac 100644
--- a/wp-includes/wp-db.php
+++ b/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 );
 	}