dyno / scala-cosmos

An example Scala 3 web application

Scala Cosmos

An example project to show multiple Scala 3 (Dotty) features in a simple web application.

This project was created to try Scala 3 in a working program, find possible use cases and meet problems that may appear while creating a "real" web application.

If you have any comments or ideas related to the project please add them to GitHub Discussions of the project - Dotty is a new thing so every input can help in learning it.

Structure

The program is a simple web application that allows the user to obtain information about celestial bodies. It is simplified not to hide Scala 3 features in a bloated code structure. Only GET HTTP method is used, the responses are encoded into JSON.

Scala 3 features

The project uses the following Scala 3 features:

1. Givens in multiple cases.
2. New enums, parametrized and not, also used to define ADT.
3. Extension methods.
4. Opaque type aliases to keep domain values.
5. Automatic type class derivation for response JSON encoding.
6. Implicit conversions in a new Scala 3 way.
7. AkkaHttp as a Scala 2 integration example.
8. Scala 3 test framework usage with givens profits.
9. The new way to define program entry point with @main annotation.
10. Union and intersection types.

Usage

This is a normal sbt project, you can compile code with sbt compile and run it with sbt "run <port number>". The unit tests are executed with sbt test.

The program accepts one argument - the port to listen. On start example requests are displayed.

For more information on the Dotty and features used in the project, please visit: dotty-reference.