Trait MainAnnotation.MainAnnotation

trait MainAnnotation[Parser[_], Result] extends StaticAnnotation

MainAnnotation provides the functionality for a compiler-generated main class. It links a compiler-generated main method (call it compiler-main) to a user written main method (user-main). The protocol of calls from compiler-main is as follows:

• create a command with the command line arguments,
• for each parameter of user-main, a call to command.argGetter, or command.varargGetter if is a final varargs parameter,
• a call to command.run with the closure of user-main applied to all arguments.

Example:

/** Sum all the numbers
 *
 *  @param first Fist number to sum
 *  @param rest The rest of the numbers to sum
 */
@myMain def sum(first: Int, second: Int = 0, rest: Int*): Int = first + second + rest.sum

generates

object foo {
  def main(args: Array[String]): Unit = {
    val mainAnnot = new myMain()
    val info = new Info(
      name = "foo.main",
      documentation = "Sum all the numbers",
      parameters = Seq(
        new Parameter("first", "scala.Int", hasDefault=false, isVarargs=false, "Fist number to sum"),
        new Parameter("rest", "scala.Int" , hasDefault=false, isVarargs=true, "The rest of the numbers to sum")
      )
    )
    val mainArgsOpt = mainAnnot.command(info, args)
    if mainArgsOpt.isDefined then
      val mainArgs = mainArgsOpt.get
      val args0 = mainAnnot.argGetter[Int](info.parameters(0), mainArgs(0), None) // using parser Int
      val args1 = mainAnnot.argGetter[Int](info.parameters(1), mainArgs(1), Some(() => sum$default$1())) // using parser Int
      val args2 = mainAnnot.varargGetter[Int](info.parameters(2), mainArgs.drop(2)) // using parser Int
      mainAnnot.run(() => sum(args0(), args1(), args2()*))
  }
}

Abstract methods

Source

def argGetter[T](param: Parameter, arg: String, defaultArgument: Option[() => T])(using Parser[T]): () => T

The getter for the idxth argument of type T

Source

def command(info: Info, args: Seq[String]): Option[Seq[String]]

Process the command arguments before parsing them.

Return Some of the sequence of arguments that will be parsed to be passed to the main method. This sequence needs to have the same length as the number of parameters of the main method (i.e. info.parameters.size). If there is a varags parameter, then the sequence must be at least of length info.parameters.size - 1.

Returns None if the arguments are invalid and parsing and run should be stopped.

Source

def run(program: () => Result): Unit

Run program if all arguments are valid if all arguments are valid

Source

def varargGetter[T](param: Parameter, args: Seq[String])(using Parser[T]): () => Seq[T]

The getter for a final varargs argument of type T*