The usage message for the innodb_compression_algorithm system variable is currently wrong.
The current usage message does not list snappy, which was added as an optional compression algorithm in MariaDB 10.1.3.
The current message looks like this:
The usage message is defined here:
You can see that the list in the usage message is hard-coded, but it is missing snappy.
Perhaps the list could instead be built dynamically from the values in the page_compression_algorithms array:
Non-supported compression algorithms are also compiled in as available options. Instead, support for the algorithm is checked at run-time in the innodb_compression_algorithm_validate() function: