Coding⏱️ 2 min read📅 2026-05-31

How to Fix: Scala: List[Future] to Future[List] disregarding failed futures

Convert List[Future] to Future[List] while disregarding failed futures in Playframework.

Quick Answer: Use `Future.sequence` with a custom combiner that ignores failed futures, or use `map` and `foldLeft` on the list of Futures.

📋 Table of Contents

  1. 💡 Why You Are Getting This Error
  2. ✅ Best Solutions to Fix It
  3. ✨ Wrapping Up

You're encountering this issue because `Future.sequence` is designed to handle successful futures, but in your case, you have a mix of successful and failed futures. The problem arises when one future fails, causing the entire sequence to fail.

💡 Why You Are Getting This Error

  • [Cause]

✅ Best Solutions to Fix It

Method 1: Using `Future.map` with a custom combiner

  1. Step 1: Create a combiner function that handles both successful and failed futures. For example, you can return an empty list for failed futures.

Method 2: Using `Future.map` with a custom filter

  1. Step 1: Create a function that filters out failed futures. You can use `future.value()` to retrieve the result of each future and check its status.

✨ Wrapping Up

To convert your list of futures to a single `Future[List[Int]]`, you can use either method 1 or method 2. Both approaches will ensure that the resulting future is composed of all successful elements from each original future, disregarding any failed ones.

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