When I have a table in a database which has a json column I can't use doctrine:schema:update --force because I get this error:
Unknown database type json requested, Doctrine\DBAL\Platforms\MySQL57Platform may not support it.
Break on exception shows this happening at \Doctrine\DBAL\Platforms\AbstractPlatform\getDoctrineTypeMapping because 'json' can't be found in $this->doctrineTypeMapping. This is initialized by the abstract function initializeDoctrineTypeMappings which in this case is implemented in \Doctrine\DBAL\Platforms\MySqlPlatform. Sure enough there is no 'json' key.
It looks like the array keys are native column types, and the array values are DBAL column types.
I know that mysql has a 'json' column type, and I know that DBAL has a 'json_array' column type. Let's take a shot in the dark...