sbt/notes/2.0.0/missing-file-error.md

Clearer error when a referenced file does not exist

If a file added to a task's inputs/outputs (e.g. Compile / resources += file("nope.txt")) does not exist, tasks such as package previously failed while hashing the task's cache key with an opaque sjsonnew.SerializationException that dumped the entire input list, with the real cause (NoSuchFileException) buried several Caused by: levels down. This was routinely mistaken for a corrupt cache.

sbt now reports the missing file directly:

[error] file referenced by the build does not exist: nope.txt

This addresses #9217.