- references
- goals of this workshop
- introduction into command line applications using scopt
- workshop
- implement command to print random number that can be long or int and positive or negative
- example:
random --positive
- example:
- run using
docker run- example
docker run scala-zio2-scopt-workshop sum -c1 2 -c2 3 - remember to first
docker:publishLocal
- example
- implement command to print random number that can be long or int and positive or negative
- command line options parsing library
- functional DSL
- scaffold
import scopt.OParser val builder = OParser.builder[Config] val parser1 = { import builder._ OParser.sequence( programName("scopt"), head("scopt", "4.x"), // command or options, // validations ) } - option
- flag
opt[Unit]("verbose") .action((_, c) => c.copy(verbose = true)) .text("verbose is a flag") - typed option
opt[Int]("foo") .abbr("f") .action((x, c) => c.copy(foo = x)) .text("foo is an integer property"), - preconfigured
help("help") // prints usage text version("version") // prints header text note("...") // add given string to the usage text- by default, when the --help or --version are invoked, they call sys.exit(0) after printing the help or version information
- arguments
- similar to options, but accepts values without
--or- - example: "sum 2 3"
- prefer options
- example
cmd("sum") .action((_, _) => Command.Sum(0, 0)) .text("sum(a, b) = a + b") .children( arg[Int]("constituent1") .abbr("c1") .action((value, command) => command.asInstanceOf[Sum].copy(component1 = value)) .text("constituent1 is an Int property"), arg[Int]("constituent2") .abbr("c2") .action((value, command) => command.asInstanceOf[Sum].copy(component2 = value)) .text("constituent2 is an Int property"), )
- similar to options, but accepts values without
- validation
opt[Int]('f', "foo") .action( (x, c) => c.copy(intValue = x) ) .validate( x => if (x > 0) success else failure("Option --foo must be >0") ) .validate( x => failure("Just because") )
- flag
- command
- used to express git branch kind of argument (name means something)
- example
cmd("update") .action((_, c) => c.copy(mode = "update")) .text("update is a command.") .children( // options )
- validation
checkConfig( c => if (c.keepalive && c.xyz) failure("xyz cannot keep alive") else success) )
- scaffold
- parsing
- basic
uses as a default
OParser.parse(parser1, args, Config()) match { case Some(config) => // do something case _ => // arguments are bad, error message will have been displayed }abstract class DefaultOEffectSetup extends OEffectSetup { override def displayToOut(msg: String): Unit = { Console.out.println(msg) } override def displayToErr(msg: String): Unit = { Console.err.println(msg) } override def reportError(msg: String): Unit = { displayToErr("Error: " + msg) } override def reportWarning(msg: String): Unit = { displayToErr("Warning: " + msg) } override def terminate(exitState: Either[String, Unit]): Unit = exitState match { case Left(_) => platform.exit(1) case Right(_) => platform.exit(0) } } - advanced
- by default, scopt emits output when needed to stderr and stdout
- if your application requires parsing arguments while not producing output directly, you may wish to intercept the side effects
- example
OParser.runParser(parser1, args, Config()) match { case (result, effects) => OParser.runEffects(effects, new DefaultOEffectSetup { // override methods here }) result match { Some(config) => // do something case _ => // arguments are bad, error message will have been displayed } }
- basic
- custom types
- example
object WeekDays extends Enumeration { type WeekDays = Value val Mon, Tue, Wed, Thur, Fri, Sat, Sun = Value } implicit val weekDaysRead: scopt.Read[WeekDays.Value] = scopt.Read.reads(WeekDays withName _) - refined types
implicit val nonZeroRead: scopt.Read[NonZeroInt] = scopt.Read.intRead.map(unsafeParseInt) private def unsafeParseInt(i: Int): NonZeroInt = refineV[NonZero](i) .fold(_ => throw new IllegalArgumentException("'" + i + "' cannot be zero."), identity)
- example