Add unified scaladoc to sbt build

project/AkkaBuild.scala

@@ -10,7 +10,9 @@ object AkkaBuild extends Build {
   lazy val akka = Project(
     id = "akka",
     base = file("."),
-    settings = buildSettings,
+    settings = buildSettings ++ Unidoc.settings ++ Seq(
+      Unidoc.unidocExclude := Seq(samples.id, tutorials.id)
+    ),
     aggregate = Seq(actor, testkit, actorTests, stm, cluster, http, slf4j, mailboxes, camel, camelTyped, samples, tutorials)
   )
 

project/Unidoc.scala

@@ -0,0 +1,51 @@
+import sbt._
+import Keys._
+import Project.Initialize
+
+object Unidoc {
+  val unidocDirectory = SettingKey[File]("unidoc-directory")
+  val unidocExclude = SettingKey[Seq[String]]("unidoc-exclude")
+  val unidocAllSources = TaskKey[Seq[Seq[File]]]("unidoc-all-sources")
+  val unidocSources = TaskKey[Seq[File]]("unidoc-sources")
+  val unidocAllClasspaths = TaskKey[Seq[Classpath]]("unidoc-all-classpaths")
+  val unidocClasspath = TaskKey[Seq[File]]("unidoc-classpath")
+  val unidoc = TaskKey[File]("unidoc", "Create unified scaladoc for all aggregates")
+
+  lazy val settings = Seq(
+    unidocDirectory <<= crossTarget / "unidoc",
+    unidocExclude := Seq.empty,
+    unidocAllSources <<= (thisProjectRef, buildStructure, unidocExclude) flatMap allSources,
+    unidocSources <<= unidocAllSources map { _.flatten },
+    unidocAllClasspaths <<= (thisProjectRef, buildStructure, unidocExclude) flatMap allClasspaths,
+    unidocClasspath <<= unidocAllClasspaths map { _.flatten.map(_.data).distinct },
+    unidoc <<= unidocTask
+  )
+
+  def allSources(projectRef: ProjectRef, structure: Load.BuildStructure, exclude: Seq[String]): Task[Seq[Seq[File]]] = {
+    val projects = aggregated(projectRef, structure, exclude)
+    projects flatMap { sources in Compile in LocalProject(_) get structure.data } join
+  }
+
+  def allClasspaths(projectRef: ProjectRef, structure: Load.BuildStructure, exclude: Seq[String]): Task[Seq[Classpath]] = {
+    val projects = aggregated(projectRef, structure, exclude)
+    projects flatMap { dependencyClasspath in Compile in LocalProject(_) get structure.data } join
+  }
+
+  def aggregated(projectRef: ProjectRef, structure: Load.BuildStructure, exclude: Seq[String]): Seq[String] = {
+    val aggregate = Project.getProject(projectRef, structure).toSeq.flatMap(_.aggregate)
+    aggregate flatMap { ref =>
+      if (exclude contains ref.project) Seq.empty
+      else ref.project +: aggregated(ref, structure, exclude)
+    }
+  }
+
+  def unidocTask: Initialize[Task[File]] = {
+    (compilers, cacheDirectory, unidocSources, unidocClasspath, unidocDirectory, scaladocOptions in Compile, streams) map {
+      (compilers, cache, sources, classpath, target, options, s) => {
+        val scaladoc = new Scaladoc(100, compilers.scalac)
+        scaladoc.cached(cache / "unidoc", "main", sources, classpath, target, options, s.log)
+        target
+      }
+    }
+  }
+}