boolean handling is confusing

[balhoff]

If an option type is boolean, and a default value of true is provided, there doesn't seem to be a way to set it to false on the command line:

[info] Starting scala interpreter...
Welcome to Scala 2.13.3 (Java HotSpot(TM) 64-Bit Server VM, Java 11.0.4).
Type in expressions for evaluation. Or try :help.

scala> import caseapp._
import caseapp._

scala> case class Options(enableFoo: Boolean = false)
class Options

scala> CaseApp.parse[Options](Seq())
val res0: Either[caseapp.core.Error,(Options, Seq[String])] = Right((Options(false),List()))

scala> CaseApp.parse[Options](Seq("--enable-foo", "true"))
val res2: Either[caseapp.core.Error,(Options, Seq[String])] = Right((Options(true),List(true)))

scala> CaseApp.parse[Options](Seq("--enable-foo", "false"))
val res3: Either[caseapp.core.Error,(Options, Seq[String])] = Right((Options(true),List(false)))

scala> case class Options2(enableFoo: Boolean = true)
class Options2

scala> CaseApp.parse[Options2](Seq("--enable-foo", "false"))
val res5: Either[caseapp.core.Error,(Options2, Seq[String])] = Right((Options2(true),List(false)))

scala> CaseApp.parse[Options2](Seq())
val res6: Either[caseapp.core.Error,(Options2, Seq[String])] = Right((Options2(true),List()))

For the case of res3 above, I would expect to be able to explicitly pass false, although I can get a false value by not providing the argument at all (e.g. res0). Unexpectedly --enable-foo false sets the value to true, because "false" is treated as an extra argument.

For the case of the default true value (Options2), there doesn't seem to be any command line that can set it to false.

[balhoff]

I did want to add that I've used several Scala command line parsers, and case-app is easily my favorite—thanks!

[alexarchambault]

@balhoff It is possible to pass an explicit value to boolean options, like --enable-foo=true or --enable-foo=false.

[balhoff]

@alexarchambault thank you for pointing that out, I completely missed that it was possible to use = between options and values. Based on the examples in the readme I thought a space was required. To me it's a little confusing that this works differently between, e.g., Boolean and String values. Is it safe then to use = for all arguments?

[alexarchambault]

Yes, = can be used for all options. = is optional for options requiring a value, such as string options. For options accepting an optional value (it's only booleans IIRC), the = is mandatory if you want to pass a value.

[balhoff]

Thanks! I'll leave it up to you if you want to go ahead and close this. It would be great to add that to the docs if it isn't somewhere already.