MYSQL_PWD env var and --mysql-password conflict - edge case with empty password

[georgi-iovchev]

The issues is that in case of using empty password (e.g. --mysql-password="") the password is being overridden by the environment variable MYSQL_PWD

How to repeat problem:

mysql#
drop database if exists sbtest; create database sbtest;
drop user if exists sbtest@localhost;
create user sbtest@localhost IDENTIFIED BY '';
grant all on sbtest.* to sbtest@localhost;

bash# 
export MYSQL_PWD="123" ; sysbench /usr/share/sysbench/oltp_read_write.lua prepare \
  --mysql-host=localhost --mysql-socket=/srv/lab/run/mysqld_lab.sock --mysql-user=sbtest \
  --mysql-password=""

sysbench 1.0.20 (using bundled LuaJIT 2.1.0-beta2)

FATAL: unable to connect to MySQL server on socket '/srv/lab/run/mysqld_lab.sock', aborting...
FATAL: error 1045: Access denied for user 'sbtest'@'localhost' (using password: YES)
FATAL: `sysbench.cmdline.call_command' function failed: /usr/share/sysbench/oltp_common.lua:83: connection creation failed

If the --mysql-password='nonempty' then it is honored properly. Example:

mysql#
drop database if exists sbtest; create database sbtest;
drop user if exists sbtest@localhost;
create user sbtest@localhost IDENTIFIED BY 'something';
grant all on sbtest.* to sbtest@localhost;

bash# 
export MYSQL_PWD="123" ; sysbench /usr/share/sysbench/oltp_read_write.lua prepare \
  --mysql-host=localhost --mysql-socket=/srv/lab/run/mysqld_lab.sock --mysql-user=sbtest \
  --mysql-password="something"

sysbench 1.0.20 (using bundled LuaJIT 2.1.0-beta2)

Creating table 'sbtest1'...
Inserting 10000 records into 'sbtest1'
Creating a secondary index on 'sbtest1'...