diesel

Generate DSLs in Java using an annotation processor and combine them all together.

Name

The name of the project is the literal spelling of DSL acronym.

Disclaimer

This library is still in development. Use it at you own risk.

Requirement

This library is based on Java 21.

Usage

The idea is to create DSLs for your application. You can annotate your interface with @Diesel and the annotation processor will generate the DSL with all the boilerplate code for you.

For example this interface:

import com.github.tonivade.diesel.Diesel;

@Diesel
public interface Console {
  String readLine();
  void writeLine(String line);
}

will be transformed into:

import com.github.tonivade.diesel.Program;
import com.github.tonivade.diesel.Result;
import javax.annotation.processing.Generated;

@Generated("com.github.tonivade.diesel.DieselAnnotationProcessor")
public sealed interface ConsoleDsl<T> extends Program.Dsl<Console, Void, T> {

  record ReadLine() implements ConsoleDsl<String> {
  }

  record WriteLine(String line) implements ConsoleDsl<Void> {
  }

  static <S extends Console, E> Program<S, E, String> readLine() {
    return (Program<S, E, String>) new ReadLine();
  }

  static <S extends Console, E> Program<S, E, Void> writeLine(String line) {
    return (Program<S, E, Void>) new WriteLine(line);
  }

  @Override
  default Result<Void, T> handle(Console state) {
    var result = (T) switch (this) {
      case ReadLine() -> state.readLine();
      case WriteLine(var line) ->  {
        state.writeLine(line);
        yield null;
      }
    };
    return Result.success(result);
  }
}

After that you could use the DSL inside a program:

public static void main(String... args) {

  var program = writeLine("What's your name?")
    .flatMap(_ -> readLine())
    .flatMap(name -> writeLine("Hello " + name + "!"));

  // output of the program:
  // >> What's your name?
  // << Toni
  // >> Hello Toni!
  program.eval(new Console() {
    public void writeLine(String line) {
      System.out.println(line);
    }
    public String readLine() {
      return System.console().readLine();
    }
  });
}