Clojure Is Simple (2017)

What I did with my first clojure web app is simply leave (main) at the end of the file. This would cause an error telling me that a port is unavailable.

But still Clojure is a lot of fun and that's something you want to look for in a language.

I find this comment puzzling, since uberjars are the normal deployment model of Clojure apps and they work well.

Are you referring to a situation where you are developing macros and end up doing something at compile time that should happen at runtime? Or maybe a situation where you put your application logic in statements outside function definitions, possibly copied from a REPL session?

That's false, building an uberjar has nothing to do wit that. If you're packaging an application typically your -main needs to be AOT compiled, that's why you put :gen-class in your ns declaration. That namespace will get AOT compiled. This still doesn't pose any issues since you shouldn't be doing such side effects in the toplevel. So

    (alter-config-file!)

is bad because that code will run during compilation, but in

    (defn -main [& args]
      (alter-config-file!)
      (app!))

it will run only after calling -main.