Shapeless VS Chimney

Scala 2-only: * Shapeless (there is Shapeless for Scala 3 but less often needed as basic things are in Scala 3)

This is the FromMap typeclass in Shapeless. Note that there’s a companion syntax package for it providing .toRecord for any Map and an appropriately-structured Record (and a Record is the LabelledGeneric representation of a case class).

If that's what you want, you can use Shapeless' records and HList. You can probably replicate this in plain Scala 3 with tuples and literal types as you said. It won't play nice with your others libs though but maybe there are integrations.

See the Shapeless Sized example.

Shapeless has Sized: https://github.com/milessabin/shapeless/blob/v2.3.9/core/src/main/scala/shapeless/sized.scala

I know that libraries like Scodec and shapeless were rewritten practically from scratch for Scala 3, taking advantage of the next syntax and internals, as well as protoquill - a Scala 3 implementation of Quill.

please show me something like this: https://akka.io/ or this: https://zio.dev/ or this: https://github.com/milessabin/shapeless

That largely depends on the type system. Languages like Haskell and Scala which have much more powerful type systems than C/Java/Go/etc absolutely do allow you to do those sorts of things. It is a bit harder to wrap your head around to be sure and there are some rough edges, but once you get the hang of it you can get the benefits of static typing with the flexibility of dynamic typing. See https://github.com/milessabin/shapeless or a project that I've been working on a lot lately https://github.com/zio/zio-schema.

Just use cats and use the apply syntax .mapN for this. Seriously. There isn't a way to do it without generating source code that I can see in the api. Scala 3's HList Tuples aren't like Shapeless 2's HLists and I can't figure out a way in the api to reduce the tuple members down from (A, B, C, D) into an E, generically, yet with Scala 3 poly functions, unlike what you could do in Shapeless 2 with HList

Scala has sparked a huge ecosystem of very high quality libraries (Cats, Scalaz, shapeless, to name but a few). I think a major reason for this is that Scala attracts developers who value the advantages of the JVM, but are fed up with the limitations of the Java programming language and understand the benefits of an expressive type system and functional programming.

But yeah, I wonder if using a tool for case classes conversion like https://github.com/scalalandio/chimney would help in managing those ADT hierarchies for DB/business logic/web layer/etc.

Hello, if you have some nice examples could you please check if it's something that would fit any of issues planned for 0.7.1 or create a new one?

Perhaps, https://github.com/scalalandio/chimney would leverage it.

Thankfully, there are some solutions that can help reduce the boilerplate of these manual conversions. For instance, chimney : https://scalalandio.github.io/chimney/

I want to upgrade one project to Scala 3.1, but I'm using the macro heavy chimney (https://github.com/scalalandio/chimney) to reduce the boilerplate, which is not available for Scala 3 yet. My idea was to copy and paste the code that chimney generates on 2.13, and after that uncomment the uses of chimney for now.

In my $dayjob we originally used Scala, but I pushed for a couple of new services to be written in TypeScript/Node as it was really hard to hire Scala developers. I'd say it worked well, we even took a somewhat functional approach to building things. We tried fp-ts but that was a bit hardcore (when you are trying to hire TypeScript developers who don't know functional programming), so just built Either and Option types which provided 99% of what we needed.

There are still a few things I miss though:

* Pattern matching and exhaustive checking. Using a switch statement it is possible to define a function that can emulate the compile-time exhaustive checking, but it's still rather weak compared to what you can do in Scala.

* Implicits. Being able to define something that can convert say a UUID to a String or vice versa automatically just feels like magic, especially when dealing with data from third party systems.

* Compiler macros and metaprogramming. It enables tools like Chimney (https://scalalandio.github.io/chimney/) to be built, which I don't think are possible with TypeScript right now.

Converting between these classes can add some boilerplate, but luckily there are libraries like https://github.com/scalalandio/chimney that make it much easier.