He-Pin opened a new pull request, #2726: URL: https://github.com/apache/pekko/pull/2726
## Motivation `Source.combine` with a single source bypasses the `fanInStrategy` entirely, performing a direct `asInstanceOf` cast. This is incorrect for strategies like `MergeLatest` where the output type differs from the input type (`T => List[T]`). For example: ```scala Source.combine(Seq(Source.single(1)))(MergeLatest(_)) // Expected: emits List(1) // Actual: emits 1 (raw Int, ClassCastException at runtime) ``` ## Modification - Try `fanInStrategy(1)` first via GraphDSL, routing through the strategy even for a single source - If the strategy throws `IllegalArgumentException` (e.g., `Concat`/`Interleave` which require >1 inputs), fall back to the original direct cast behavior (safe because those strategies always have `T == U`) - Added 4 Scala tests and 1 Java test covering `MergeLatest`, `Merge`, and `Concat` with single source ## Result `Source.combine(Seq(source))(MergeLatest(_))` now correctly emits `List[T]` instead of raw `T`. Existing behavior for `Merge`, `Concat`, etc. is preserved. ## References - Fixes https://github.com/apache/pekko/issues/2723 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
