scopt-auto

Scopt-auto is an attempt to automatically create a scopt parser for a case class representing the target configuration.

The main ideas are:

Parameters in the case class with default values becomes optional command line options. Parameters without default values become mandatory command line options.
Nested case classes should be supported. This way these nested case classes can represent frequently re-used configurations without copy/paste.

The practical reality is:

A camelCase parameter in a case class becomes a --snake-case argument.
A parameter in a nested case class is represented by the dot notation (.) in the parser option. So for example config.nestedConfig.nestedSetting (config here is a value of our configuration case class) becomes the command line option --nested-config.nested-setting.
Only one level of case class nesting is supported, simply because i couldn't find out how to do a second level using shapeless.
To create a command line option that is optional without a default value use a case class parameter of type Option[T] with default value None.
No Scala 3 support, we aren't using it yet...

A simple example:

scala> :paste
// Entering paste mode (ctrl-D to finish)

import com.tresata.scopt.auto.Options

case class Cpu(mhz: Int, cores: Int = 4)
case class Drive(size: Int, opal: Boolean = false)
case class Laptop(serial: Option[String] = None, cpu: Cpu, drive: Drive)

// Exiting paste mode, now interpreting.

import com.tresata.scopt.auto.Options
class Cpu
class Drive
class Laptop

scala> Options[Laptop].parse("--cpu.mhz 3000 --drive.size 2000")
val res0: Laptop = Laptop(None,Cpu(3000,4),Drive(2000,false))

scala> Options[Laptop].parse("--serial 123456 --cpu.mhz 2000 --cpu.cores 2 --drive.size 1000 --drive.opal true")
val res1: Laptop = Laptop(Some(123456),Cpu(2000,2),Drive(1000,true))

scala> Options[Laptop].parser
val res2: scopt.OParser[_, Laptop] = scopt.OParser@54812c74

scala> Options[Laptop].parse("--serial 123456 --cpu.mhz 2000 --drive.opal true")
Error: Missing option --drive.size
Try --help for more information.
java.lang.IllegalArgumentException: invalid arguments
  at com.tresata.scopt.auto.Options$$anon$1.parse(Options.scala:40)
  ...

scala> Options[Laptop].parse("--help")
Usage:  [options]

  --serial <value>      optional String
  --cpu.mhz <value>     required Int
  --cpu.cores <value>   optional Int (default 4)
  --drive.size <value>  required Int
  --drive.opal <value>  optional Boolean (default false)
  --help

Have fun! Team @ Tresata

tresata / scopt-auto

scopt-auto

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