Why does my sourceDirectories setting have no effect in sbt?

Question

I'm reading the SBT Getting Started guide. That page shows the sourceDirectories setting as an example. To try it myself, I put the following in my build.sbt file, for a basic "hello world" project.

sourceDirectories in Compile := Seq(file("other"))

(Appending with += or ++= doesn't work either.)

I have source files in <base-dir>/other and in <base-dir>/src/main/scala. I ran sbt and typed compile. It ignored the setting:

> compile
[info] Compiling 1 Scala source to /Learning/Scala/proj1/target/scala-2.9.2/classes...
[error] /Learning/Scala/proj1/src/main/scala/hello.scala:7: not found: value Foo
[error]     println(Foo.foo)

The Foo object is defined in foo.scala in the other source directory.

What am I missing?

Answer 1

tl;dr The answer by @schleichardt is a valid one - you need to add the following to the build.sbt file:

unmanagedSourceDirectories in Compile += file("other")

The explanation boils down to inspecting the dependencies of the compile task. Use inspect tree compile to find them out.

[proj1]> inspect tree compile
[info] compile:compile = Task[sbt.inc.Analysis]
[info]   +-compile:compile::compileInputs = Task[sbt.Compiler$Inputs]
[info]   | +-compile:scalacOptions = Task[scala.collection.Seq[java.lang.String]]
[info]   | +-compile:sources = Task[scala.collection.Seq[java.io.File]]
[info]   | +-*/*:sourcePositionMappers = Task[scala.collection.Seq[scala.Function1[xsbti.Position, scala.Option[xsbti.Position]]]]
[info]   | +-*/*:maxErrors = 100
[info]   | +-*:compilers = Task[sbt.Compiler$Compilers]
[info]   | +-compile:compile::streams = Task[sbt.std.TaskStreams[sbt.Init$ScopedKey[_ <: Any]]]
[info]   | | +-*/*:streamsManager = Task[sbt.std.Streams[sbt.Init$ScopedKey[_ <: Any]]]
[info]   | |
[info]   | +-compile:incCompileSetup = Task[sbt.Compiler$IncSetup]
[info]   | +-*/*:compileOrder = Mixed
[info]   | +-compile:dependencyClasspath = Task[scala.collection.Seq[sbt.Attributed[java.io.File]]]
[info]   | +-compile:classDirectory = target/scala-2.10/classes
[info]   | +-*/*:javacOptions = Task[scala.collection.Seq[java.lang.String]]
[info]   |
[info]   +-compile:compile::streams = Task[sbt.std.TaskStreams[sbt.Init$ScopedKey[_ <: Any]]]
[info]     +-*/*:streamsManager = Task[sbt.std.Streams[sbt.Init$ScopedKey[_ <: Any]]]
[info]

As you can see, the task depends on the compile:sources task. The task in turn depends on the compile:unmanagedSources task that uses the compile:unmanagedSourceDirectories setting.

[proj1]> inspect tree compile:sources
[info] compile:sources = Task[scala.collection.Seq[java.io.File]]
[info]   +-compile:unmanagedSources = Task[scala.collection.Seq[java.io.File]]
[info]   | +-compile:unmanagedSourceDirectories = List(/Users/jacek/sandbox/stackoverflow/proj1/src/main/scala, /Users/jacek/sandbox/stackoverflow/proj1/src/main/java, /Users/..
[info]   | | +-compile:javaSource = src/main/java
[info]   | | | +-compile:sourceDirectory = src/main
[info]   | | |   +-*:sourceDirectory = src
[info]   | | |   | +-*:baseDirectory = /Users/jacek/sandbox/stackoverflow/proj1
[info]   | | |   |   +-*:thisProject = Project(id: proj1, base: /Users/jacek/sandbox/stackoverflow/proj1, aggregate: List(), dependencies: List(), configurations: List(compile..
[info]   | | |   |
[info]   | | |   +-compile:configuration = compile
[info]   | | |
[info]   | | +-compile:scalaSource = src/main/scala
[info]   | | | +-compile:sourceDirectory = src/main
[info]   | | |   +-*:sourceDirectory = src
[info]   | | |   | +-*:baseDirectory = /Users/jacek/sandbox/stackoverflow/proj1
[info]   | | |   |   +-*:thisProject = Project(id: proj1, base: /Users/jacek/sandbox/stackoverflow/proj1, aggregate: List(), dependencies: List(), configurations: List(compile..
[info]   | | |   |
[info]   | | |   +-compile:configuration = compile
[info]   | | |
[info]   | | +-*:baseDirectory = /Users/jacek/sandbox/stackoverflow/proj1
[info]   | |   +-*:thisProject = Project(id: proj1, base: /Users/jacek/sandbox/stackoverflow/proj1, aggregate: List(), dependencies: List(), configurations: List(compile, runt..
[info]   | |
[info]   | +-*/*:excludeFilter = sbt.SimpleFileFilter@7ced8ea7
[info]   | +-*:baseDirectory = /Users/jacek/sandbox/stackoverflow/proj1
[info]   | +-*/*:unmanagedSources::includeFilter = sbt.SimpleFilter@1beb6bba
[info]   | +-*/*:sourcesInBase = true
[info]   |
[info]   +-compile:managedSources = Task[scala.collection.Seq[java.io.File]]
[info]     +-compile:sourceGenerators = List()
[info]

The compile:unmanagedSourceDirectories setting references "Unmanaged source directories, which contain manually created sources."

[proj1]> inspect compile:unmanagedSourceDirectories
[info] Setting: scala.collection.Seq[java.io.File] = List(/Users/jacek/sandbox/stackoverflow/proj1/src/main/scala, /Users/jacek/sandbox/stackoverflow/proj1/src/main/java, /Users/jacek/sandbox/stackoverflow/proj1/other)
[info] Description:
[info]  Unmanaged source directories, which contain manually created sources.
[info] Provided by:
[info]  {file:/Users/jacek/sandbox/stackoverflow/proj1/}proj1/compile:unmanagedSourceDirectories
[info] Defined at:
[info]  (sbt.Defaults) Defaults.scala:161
[info]  /Users/jacek/sandbox/stackoverflow/proj1/build.sbt:1
[info] Dependencies:
[info]  compile:javaSource
[info]  compile:scalaSource
[info]  *:baseDirectory
[info] Reverse dependencies:
[info]  compile:unmanagedSources
[info]  compile:sourceDirectories
[info] Delegates:
[info]  compile:unmanagedSourceDirectories
[info]  *:unmanagedSourceDirectories
[info]  {.}/compile:unmanagedSourceDirectories
[info]  {.}/*:unmanagedSourceDirectories
[info]  */compile:unmanagedSourceDirectories
[info]  */*:unmanagedSourceDirectories
[info] Related:
[info]  test:unmanagedSourceDirectories

The setting is of the scala.collection.Seq[java.io.File] type and to append an element to the seq, you can use += method.

Having said that, the build.sbt file should be as follows:

unmanagedSourceDirectories in Compile += (baseDirectory / "other").value

You don't have to use the baseDirectory setting, but it makes the base directory explicit.

Answer 2

You can try this:

unmanagedSourceDirectories in Compile += file("other")