Pass $allow_bail to fallback attempt in $wpdb->db_connect

[bobbywalters]

When a database connection can not be established and a fallback call is attempted the value of $allow_bail is not passed to the second call of db_connect. This means the fallback attempt will always bail.

This is the line of concern:
https://core.trac.wordpress.org/browser/tags/4.2.4/src/wp-includes/wp-db.php#L1468

Changing from:

if ( $attempt_fallback ) {
	$this->use_mysqli = false;
	$this->db_connect();
}

to

if ( $attempt_fallback ) {
	$this->use_mysqli = false;
	$this->db_connect( $allow_bail );
}

Will honor the $allow_bail value from the original call to be passed to the fallback attempt if it is necessary.

A test scenario is:

1. Verify the database is NOT running so all connection attempts fail.
2. A sample script PHP script that would verify the $allow_bail flag is passed along to the fallback attempt:

<?php
define('SHORTINIT', true);
define('WP_DEBUG', true); // triggers $wpdb->show_errors()
define('WP_SETUP_CONFIG', true); // prevents db_connect() call within new wpdb(...)

require 'wp-config.php';

global $wpdb;
echo "Calling wpdb->db_connect( false )...\n";
$wpdb->db_connect( false );
echo "wpdb->bail() was not called because you can see me!\n";

A work around is possible by calling

$wpdb->hide_errors();

or ensuring WP_DEBUG is not true (calling hide_errors() is safer since you can't undefine a constant) prior to

$wpdb->db_connect();

but this goes further down the error handling path than it needs to.

I can provide additional information if necessary. Thanks in advance for taking a look at this.

[chriscct7]

Introduced in 3.9 in [27935]

[chriscct7]

Your proposed fix looks good. 4.3 goes out tomorrow, but once the 4.4 branch is setup, I'll go ahead and write the patch file for this

[bobbywalters]

Replying to chriscct7:

Your proposed fix looks good. 4.3 goes out tomorrow, but once the 4.4 branch is setup, I'll go ahead and write the patch file for this

Sounds good. Thanks for the quick response.

[wonderboymusic]

move back if a patch materializes

[chriscct7]

@wonderboymusic, the patch while not in a patch file is in the description of the ticket itself. I can take care of making it into a formal patch file.

[johnbillion]

[34478]