If the pgstac_settings default-filter-lang is set to cql-json, I don't believe it can be overridden as intended by this line:

In the case where the default is set to "cql-json" and the client sends a filter-lang property of "cql2-json", I read the logic of that lines as (false or true) and it then attempts and fails to parse the cql2 as cql (which is the behavior I'm seeing). Instead, I think the default just need to be checked is the search didn't provide a filter-lang property.

If the default is set to cql2-json, the search-supplied and override behavior seems correct.