> Scala is a language I find interesting. Between Spark, Akka, and all of the FP, it seems like it has most of the boxes I’d want. I have read mixed things about the language though, specifically with respect to its future viability and development. Is Scala worth learning in 2020?

Scala has always attracted an outsized amount of hate and FUD. That said, Scala 3 has taken a long time to arrive, costing the language a lot of momentum, and makes some fairly radical changes.

I'm a huge fan of Scala and I really want it to succeed. Haskell's laziness is a dealbreaker IMO (it makes it impossible to reason about performance), and no other language offers the combination of:

1. A type system powerful enough to replace all your uses of reflection/AOP/metaclassing/etc.. No more magic frameworks to learn; write real-world business applications using nothing but plain old functions and values that follow the normal rules of the language (e.g. your web routes can be literally a function from request to response; they don't look quite as nice as a dedicated routing config file would, but they're normal code that automated refactoring etc. will work normally on). Concretely, what makes this possible is the combination of higher-kinded types (letting you represent any custom effect, e.g. a database transaction, as an F[_] type, and then use the language's for/yield syntax to compose those effects in a way that makes them visible but not overly verbose/intrusive), and records (letting you "walk the object graph" in a type-safe way). Scala can do all this without having to resort to general-purpose macros (there is one macro in shapeless that the whole rest of the ecosystem just reuses), so you can be confident that your IDE/debuggers/etc. will all understand your code.

2. A proper first-class IDE, and a good declarative build tool integrated fully with that IDE (maven - for some reason the Scala community pushes the incomprehensible SBT, but ignore that).

3. Completely seamless compile-to-javascript experience. You write normal code, push the button, and there it is running in your browser. When you want to use a library you import typescript type definitions with https://scalablytyped.org/ and it all just works. Combined with the previous point that means Scala is actually the best language to use for frontend development right now. Unfortunately the set of people who know about Scala and the set of people who do frontend development don't really overlap.

I'm not wedded to Scala for the sake of Scala. But no other language comes close.

All that said, it definitely feels like the next year or two could be a turning point (in either direction) for the popularity of the language. Scala 3 may revitalise scala or destroy it. So it's undeniably a risk. But I'd say that even if the language becomes less popular, learning it will make you a better programmer and give you an appreciation for what's possible.