sbt : Is there a better way of structuring large build.sbt files - scala

Question

Problem description: large sbt file
Our current build.sbt spanns 250+ lines.
We have two problems:
readability
current approach grouping of data and comments:
// Plugins ///////////////////////////////////////////////////
enablePlugins(DockerPlugin)
// basic configuration : projects ///////////////////////////
name := """projectName"""
lazy val projectName =
(project in file(".")).....
logic reuse
We have some configuration logic we would like to share between different projects.
Question
Is there a way to include other *.sbt files?
Or do you have a suggestion how to solve this problem without resorting to write a sbt plugin?

Answer 1

Is there a way to include other *.sbt files?
Yes, you can simply put parts of your build.sbt file into other *.sbt files within your project root. SBT picks up all *.sbt files and merges them together, as there was only a single large file.

Answer 2

One thing you can do is to factor out parts of your build info into scala files in the project directory.
E.g. in our build we have a file Dependencies.scala in the project directory, which contains all dependencies of the various projects in one place:
object Dependencies {
val akka_actor = "com.typesafe.akka" %% "akka-actor" % "2.3.13"
// ...
}
This can then be imported from the build.sbt:
import Dependencies._
lazy val foo = Project(...) dependsOn (akka_actor, ...)
You can also put tasks and commands into objects in the project directory.
Update: One thing I often do when looking for inspiration about how to organize a build is to look at the build of complex, high-profile scala projects such as akka. As you can see, they have moved a lot of logic into scala files in the project directory. The build itself is defined in AkkaBuild.scala.