My impression is that PureScript aims to not be configurable. For example, the compiler does not allow you to disable warnings. Other tools, like `psa`, can do that, but the base language is always the same.

Specifically related to language extensions, there is this wiki page: https://github.com/purescript/purescript/wiki/Differences-fr...

> The PureScript compiler does not support GHC-like language extensions.