Question 1

How to parse key-value pairs with scopt in Scala?

Accepted Answer

Use opt[Map[String, String]]("kwargs") in your parser definition. It accepts comma-separated pairs like --kwargs key1=val1,key2=val2 and maps them to a Scala Map in your Config case class, as shown in the functional DSL example.

Question 2

scopt vs decline: which is better for Scala CLI tools?

Accepted Answer

scopt offers richer features like commands and automatic help generation out of the box, while decline is more minimalist and purely functional. Choose scopt for complex, nested CLIs; decline for simpler, composable argument parsing without extra dependencies.

Question 3

How to hide options from help text in scopt?

Accepted Answer

Apply the hidden() method to an option definition, e.g., opt[Unit]("debug").hidden(). This keeps the option functional but excludes it from generated usage text, useful for internal flags, as demonstrated in the README.

Question 4

Can I use scopt with Scala Native for command-line tools?

Accepted Answer

Yes, scopt supports Scala Native for versions 0.4.x and 0.3.x, as indicated in the compatibility table. Add it as a dependency in your build.sbt to build native CLI applications with type-safe argument parsing.

Question 5

How to add custom validation for options in scopt?

Accepted Answer

Use the validate method on an option or checkConfig for overall validation. For example, opt[Int]("foo").validate(x => if (x > 0) success else failure("must be positive")) ensures positive values, with error messages displayed on failure.

Question 6

What's the difference between functional and object-oriented DSL in scopt?

Accepted Answer

The functional DSL uses OParser with a sequence-based declarative style, while the OO DSL extends OptionParser for an imperative approach. Functional DSL is more modern and composable; OO DSL is backward-compatible with scopt 3.x, but both handle parsing similarly.

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