👀 Views: 70 💬 Answers: 1 📅 Created: 2025-07-02

scala option lazy-evaluation for-comprehension Scala

I need help solving I'm running into an scenario with lazy evaluation in a for-comprehension while trying to work with `Option` in Scala 2.13.3... My expectation was that the for-comprehension would short-circuit as soon as it encounters a `None`, but it seems to be evaluating all parts regardless. Here's a simplified version of my code: ```scala case class User(id: Int, name: String) def getUserById(id: Int): Option[User] = { if (id == 1) Some(User(1, "Alice")) else None } def getUserNameById(id: Int): Option[String] = { for { user <- getUserById(id) } yield user.name } } val userName = getUserNameById(2) println(userName) // Should output None but leads to unexpected behavior ``` In this case, I'm expecting `userName` to be `None` since `getUserById(2)` should return `None`. However, if I put additional logic inside the for-comprehension, such as printing out the user before yielding their name, it executes that code even when `getUserById` returns `None`. I've tried wrapping `getUserById` in a `if` check, but it feels like I'm circumventing the benefits of using a for-comprehension. From what I understand, the for-comprehension should handle this gracefully, and I’m wondering if there’s an scenario with how I’m structuring my code. Is there a way to ensure that evaluation short-circuits properly without losing the elegance of the for-comprehension? Any insights would be appreciated! This is my first time working with Scala 3.10. What's the best practice here? Is this even possible? I'm using Scala stable in this project. Am I missing something obvious?