Is there an idiomatic Haskell?

The question of “best practices” is something that comes up very often, and I am afraid this isn’t really a thing in Haskell at this time.

For example, every codebase I’ve touched has had a different logging solution. Some people like to use mtl, but others prefer the use of transformers directly. There are many powerful database libraries available.

There are things that come up more often than others – for example, I’ve never seen command-line parsers other than optparse-applicative, although other seemingly high-quality alternatives exist. Likewise, amazonka is the fully-featured AWS client.

It’s a bit of a rambling answer to tell you that there is no such thing as a single vision of idiomatic Haskell, as far as I know. This can be both terrifying and freeing! Go ahead and do what feels right. One of the main benefits of Haskell is that it’ll be easy to refactor if you change your mind.