Avoid SBT macro recompilation issue

server/src/main/scala/controllers/Application.scala

@@ -1,21 +1,15 @@
 package controllers
 
-import java.nio.ByteBuffer
-
-import boopickle.Default._
 import play.api.mvc._
-import services.ApiService
+import services.ApiServer
+import services.ApiServer._
 import spatutorial.shared.Api
 
 import scala.concurrent.ExecutionContext.Implicits.global
 
-object Router extends autowire.Server[ByteBuffer, Pickler, Pickler] {
-  override def read[R: Pickler](p: ByteBuffer) = Unpickle[R].fromBytes(p)
-  override def write[R: Pickler](r: R) = Pickle.intoBytes(r)
-}
 
 object Application extends Controller {
-  val apiService = new ApiService()
+
 
   def index = Action {
     Ok(views.html.index("SPA tutorial"))
@@ -29,13 +23,8 @@ object Application extends Controller {
       val b = request.body.asBytes(parse.UNLIMITED).get
 
       // call Autowire route
-      Router.route[Api](apiService)(
-        autowire.Core.Request(path.split("/"), Unpickle[Map[String, ByteBuffer]].fromBytes(ByteBuffer.wrap(b)))
-      ).map(buffer => {
-        val data = Array.ofDim[Byte](buffer.remaining())
-        buffer.get(data)
-        Ok(data)
-      })
+      ApiServer.route(path, b).map(Ok(_))
+
   }
 
   def logging = Action(parse.anyContent) {

server/src/main/scala/services/ApiServer.scala

@@ -0,0 +1,85 @@
+package services
+
+import java.util.{UUID, Date}
+
+import scala.concurrent.Future
+import scala.concurrent.ExecutionContext.Implicits.global
+
+import spatutorial.shared._
+import java.nio.ByteBuffer
+
+import boopickle.Default._
+
+object ApiServer {
+
+  val apiService = new ApiService()
+
+  object Router extends autowire.Server[ByteBuffer, Pickler, Pickler] {
+    override def read[R: Pickler](p: ByteBuffer) = Unpickle[R].fromBytes(p)
+    override def write[R: Pickler](r: R) = Pickle.intoBytes(r)
+  }
+
+  /*
+   * NOTE:
+   *
+   * SBT appears to have an issue in not incrementally compiling macros when its
+   * dependents changes. So in this case, the Router is dependent on Api trait,
+   * and if that trait changes, all invocation to the Router needs to be recompiled.
+   * The original Router invocation was in Application, but Application will probably
+   * not change when you change the Api service. As a work-around, move it here because
+   * if you change the Api trait, you will need to change the ApiService implementation,
+   * so this entire file (including the router invocation) would have to be recompiled.
+   */
+  def route(path: String, b: Array[Byte]): Future[Array[Byte]] = {
+    Router.route[Api](apiService)(
+      autowire.Core.Request(path.split("/"), Unpickle[Map[String, ByteBuffer]].fromBytes(ByteBuffer.wrap(b)))
+    ).map(buffer => {
+      val data = Array.ofDim[Byte](buffer.remaining())
+      buffer.get(data)
+      data
+    })
+  }
+
+  class ApiService extends Api {
+    var todos = Seq(
+      TodoItem("41424344-4546-4748-494a-4b4c4d4e4f50", 0x61626364, "Wear shirt that says “Life”. Hand out lemons on street corner.", TodoLow, false),
+      TodoItem("2", 0x61626364, "Make vanilla pudding. Put in mayo jar. Eat in public.", TodoNormal, false),
+      TodoItem("3", 0x61626364, "Walk away slowly from an explosion without looking back.", TodoHigh, false),
+      TodoItem("4", 0x61626364, "Sneeze in front of the pope. Get blessed.", TodoNormal, true)
+    )
+
+    override def motd(name: String): String = s"Welcome to SPA, $name! Time is now ${new Date}"
+
+    override def getTodos(): Seq[TodoItem] = {
+      // provide some fake Todos
+      println(s"Sending ${todos.size} Todo items")
+      todos
+    }
+
+    // update a Todo
+    override def updateTodo(item: TodoItem): Seq[TodoItem] = {
+      // TODO, update database etc :)
+      if (todos.exists(_.id == item.id)) {
+        todos = todos.collect {
+          case i if i.id == item.id => item
+          case i => i
+        }
+        println(s"Todo item was updated: $item")
+      } else {
+        // add a new item
+        val newItem = item.copy(id = UUID.randomUUID().toString)
+        todos :+= newItem
+        println(s"Todo item was added: $newItem")
+      }
+      todos
+    }
+
+    // delete a Todo
+    override def deleteTodo(itemId: String): Seq[TodoItem] = {
+      println(s"Deleting item with id = $itemId")
+      todos = todos.filterNot(_.id == itemId)
+      todos
+    }
+  }
+
+}