Ask HN: How to keep Scala codebase idiomatic?

Clever people often get seduced by the expressive power of the language and start writing Haskell in Scala.

Well said in Effective Scala [1]: "Above all, program in Scala. You are not writing Java, nor Haskell, nor Python; a Scala program is unlike one written in any of these. In order to use the language effectively, you must phrase your problems in its terms. There’s no use coercing a Java program into Scala, for it will be inferior in most ways to its original."

While pure FP code can be a good fit for some projects, it makes hiring much harder. IMO, it is never going to be key component of project's success, but can be a significant contributor to its failure.

Good examples of what I consider idiomatic Scala are projects from Odersky, Haoyi and Twitter.

Most of closed-source projects I've seen are either Java or Haskell projects in disguise.

What is you experience with Scala projects in this regard? Did you choose idiomatic mix of FP and OOP or some other approach?

[1] https://twitter.github.io/effectivescala/