We need to define to which extent MariaDB 10.2 should be compatible with MySQL 5.7.
For MariaDB 10.0/10.1 the major obstacle is
MDEV-9904 (closed as "Won't fix").
For MariaDB 10.2, it is not a problem after InnoDB 5.7 has been merged; but it still can't start on MySQL 5.7 datadir due to
I expect there will be other issues, so this entry will be an umbrella bug until we are satisfied with the level of compatibility we provide.
This section will contain random features, syntax and options that I encounter during testing as not supported in 10.2, while supported in MySQL 5.7.
It is not intended to be a full list!