Is there a recommended way to handle exceptions within an `either {}` comprehensions and map those e...

# arrow

[Michael Friend]

Is there a recommended way to handle exceptions within an either {} comprehensions and map those exceptions to a Left value? Right now i have something like this where i just catch the exception with Either.catch and map it to the right left type

suspend fun foo(): Either<String, List<Data>> = either { 
   val data = api.getData().bind()
   return@either Either.catch { doFileStuff }.mapLeft { it.message }
}

[simon.vergauwen]

Either.catch and mapLeft is the most common way of doing that and is considered idiomatic usage. In 1.1.6-alpha.28, will be released next month as 1.2.0, we've added catch as a DSL. That'll allow you to do:

either {
  val res = catch({ doFileStuff() }) { ex: Throwable ->
    raise(it.message)
    // fallback value
  }
    val res2 = catch({ doFileStuff() }) { ex: FileNotFountException ->
    raise("file-not-found")
    // fallback value
  }
}

[Michael Friend]

nice i like that DSL inside either. Thanks!