access to other args in validation functions

[zero-sum]

Is there a way to allow validation functions access to other arguments?

For instance, if there is an arg specifying an "output file" I could evaluate it more accurately during validation if I was aware that option "--overwriteExisting" were also set.

[eed3si9n]

How would it look like?

arg[File]("<file>...") unbounded() optional() action { (x, c) =>
    c.copy(files = c.files :+ x) } text("optional unbounded args") validateWithConfig { (x, c) =>
      if (c.overwriteExisting) failure("The file doesn't exist")
      else success
    }

Something like the above?

[zero-sum]

Perfect!

Only one question -- could precedence (e.g. the arg depends on the opt already having been parsed) be handled simply by the order in which they are defined in the parser declaration? Or would some sort of internal DAG need to be used.

[eed3si9n]

The way it works now is that they are processed in the order it was passed, so you'd need to use Option[T] or something to track options and validate them when all are filled in.

[zero-sum]

Not exactly sure how this would work. Maybe I am misunderstanding something?

".. -overwriteExisting <file> .."
-overwriteExisting will be set to either None or Some[Boolean], enabling validation of <file>
".. <file> -overwriteExisting .." // preferred usage
-overwriteExisting will not be set at the time of file validation. <file> could be validated during -overwriteExisting validation, but only if -overwriteExisting (which is optional) is used

I can think of a couple solutions:

• Provide the ability for a final validation pass after all args have been parsed
• Define -overwriteExisting as a child of <file>, and then enforce processing of of children before processing of parent. e.g.

arg[File]("<output path>")
  .text("The output location")
  .children(
    opt[Unit]("overwrite") 
    abbr("o")   
    action { (_, c) => c.copy(overwriteOutputPath = false) } 
    text("overwrite output path")
  )
  .action { (x, c) => c.copy(outputPath = x) }
  .validateWithConfig{ (x,c) => // perform file validation using c.overwriteExisting }

[eed3si9n]

Added a standalone checkConfig construct. This can also be nested within children.

val parser = new scopt.OptionParser[Config]("scopt") {
  head("scopt", "3.x")
  opt[Unit]('k', "keepalive") action { (x, c) =>
    c.copy(keepalive= true) }
  opt[Boolean]("xyz") action { (x, c) =>
    c.copy(xyz = x) } text("xyz is a boolean property"),
  checkConfig { c =>
    if (c.keepalive && c.xyz) failure("xyz cannot keep alive") else success }
}

It's available as 3.2.0-SNAPSHOT if you wanna give it a shot.

[eed3si9n]

3.2.0 is out.

[zero-sum]

Thanks, works great.