tapir VS Ammonite-Ops

You're not confined to the usual suggestions below (play, http4s). There's a ton of options. (I wrote test cases using a bunch of different frameworks a few years ago at https://github.com/hohonuuli/msdemos). Having written services using a variety of frameworks in production, I would strongly suggest using one that auto-generates API docs (openapi, swagger) for you. That will save you a huge amount of time later on. For heavier services, like the one at https://fathomnet.org/, I tend to the Java side (Quarkus is my current top choice, but Micronaut and Helidon are both great). For everything else I use Scala. My go-to right now is tapir using a vertx backend. See https://tapir.softwaremill.com/

Tapir is a Scala framework. (which runs on the JDK) Since the recent release of version 1.0, it's become my go to for many projects. It doens't provide much in the way of integrations with 3rd party frameworks, but I actually prefer that. It does autogenerate great swagger docs though.

I do wonder where the recommendation to use http4s for beginners came from. http4s is a very capable library (and if you care much about composition it is excellent), but I wouldn't describe the documentation as beginner friendly.

A slightly better starting point for scala 3 + type-safe server building is tapir e.g. https://github.com/softwaremill/tapir/blob/master/examples3/... . With that, you get a declarative definition of your endpoints (+ error types, auth, etc.) that you can use for both servers and clients, which comes very handy when writing integration tests of course.

> absolutely ridiculous the fetishization of extremely complex FP and type-level hacking that goes on in the ecosystem

An alternative way to look at it is that there is a lot of essential domain complexity that gets encoded via the type system to let the compiler do the hard work. That "extremely complex FP" does not arrive out of nowhere - I really recommend at least skimming through the slides from rossabaker, the http4s designer, that motivate where the core type signature comes from https://rossabaker.github.io/boston-http4s/#2

I suppose one of the "features" that I like about the (typelevel) community is that the approach of "worse is better" is not taken, and a lot of effort is expended to make things correct, modular and orthogonal. This has the drawback of increased upfront complexity, that anecdotally pays off the moment your compiler does not error and the program runs as intended.

Did you try tapir? There is a module for deploying aws lambda with Scala js. Not sure whether it is compatible with Scala 3, I am sticking with Scala 2 until Scala 3 gets more mature.

I'm aware, but it's a design decision that was made on purpose, and which I find in practice not a big problem at all.

Backend is source of truth for types on frontend (backend generated OpenAPI definition with tapir, frontend takes it with orval)

In all cases I would strongly suggest to have a look at Tapir, regardless of the server implementation that you pick.

Check the infographic below, to see this tool history, functionalities and more. Make sure, to take tAPIr for a spin here and share your feedback with us in the comment section!

Tapir is awesome, and you can pick the server backend according to your preferred ecosystem (for instance http4s + doobie, Zio + Quill, Akka + Slick, ...)

Finally I would strongly recommend having a look at Tapir. Even if you don't need to share endpoints or generate OpenAPI documentation, it provides a really neat abstraction on top of http4s.

The indent based syntax is only available in Scala 3, you have to download a matching ammonite version from https://github.com/com-lihaoyi/Ammonite/releases

That's funny, because this is what I really like about Scala; how quick and easy it is to get a project started.

> sbt new scala/scala3.g8

will just create an empty project. If you don't even want to bother with a project, use use scala-cli or ammonite (http://ammonite.io/) to just start banging out code.

Even the upgrading of a project from Scala2 to Scala3 is a breeze, thanks to very good backwards compatibility of new library releases.

Ammonite is a very good REPL for Scala. You can invoke it with amm and type expressions into it, or load a Scala “script file” whose name ends with .sc into it, or many other things. It’s documented at https://ammonite.io. 2. sbt is the dominant build tool for Scala projects. As others have commented, when you open a folder in Visual Studio Code and try to make Metals “aware of it,” it expects to find a “Scala project” in the folder. A “Scala project” isn’t just Scala source code. See https://www.scala-sbt.org for details. 3. Also be aware that Metals supports worksheets, so you can easily experiment with code in your project interactively, too.

Scripting API is quite limited, so the third option. - reuse the ammonite scripts https://github.com/com-lihaoyi/Ammonite or look how this is implemented (using internal compiler API),

Your exposure to Functional Programming with Haskell and Clojure suggest you will certainly pick up Scala quickly. With ZIO and cats, you can write robust software quickly. Consider the excellent Coursera Scala course. Get "the Red Book" https://www.manning.com/books/functional-programming-in-scala, and most important, play. Experiment to see how things work. Get https://ammonite.io/

Here's an example of a smaller project that added telemetry without suffering a fork:

https://github.com/com-lihaoyi/Ammonite/issues/607

Or ammonite - I've ran Gatling performance test from a simple script based on this gist it fetches all the dependencies, compiles and runs the test, producing nice html report..

Scala with the Typelevel ecosystem. Stay on the jVM, but have a much more pleasant and robust experience, including a great REPL.