added toOption member to Flag for use in for comprehensions

[klaeufer]

Signed-off-by: Konstantin Läufer klaeufer@gmail.com

Example:

      for {
        true <- OptionT.fromOption[Try](options.createDatabase.toOption)
        () <- withDAO { dao => dao.createDatabase() }
      } yield printMessageFormat("created")

In context:

https://github.com/LoyolaChicagoCode/worddb-slick-scala/blob/main/src/main/scala/Main.scala#L62-L65

[lihaoyi]

This is kind of odd; Flag is basically a glorified Boolean. Converting it into an Option[true] seems like a pretty obscure use case that I don't think needs to be part of the library (though feel free to implement it in your own code!)

[klaeufer]

Good point: one could make a similar argument for Boolean to support toOption. The only use case I can think of is for starting a for-comprehension for Option like in my example because if it's further down in the for-comprehension, one can simply use a filter. So I agree that this would be a bit obscure but not all that uncommon when the first step of the for-comprehension is to check whether a particular flag is set.