How to avoid activator executing compile task twice upon accessing Play page?

Question

I am trying to run a custom task before compilation of a Play 2.3 application. I have this in my build.sbt file:

lazy val helloTask = TaskKey[Unit]("hello", "hello")

helloTask := {
  println("hello test")
}

(compile in Compile) <<= (compile in Compile) dependsOn helloTask

When I run activator ~run and then open a page in the browser, I get the following output:

C:\Development\test>activator ~run
[info] Loading project definition from C:\Development\test\project
[info] Set current project to play (in build file:/C:/Development/test/)

--- (Running the application from SBT, auto-reloading is enabled) ---

[info] play - Listening for HTTP on /0:0:0:0:0:0:0:0:9000

(Server started, use Ctrl+D to stop and go back to the console...)

hello test
[success] Compiled in 418ms
hello test
hello test
[info] play - Application started (Dev)

It seems my custom task is running three times. Is there a way I can avoid this?

Alack

Interesting. It appears that loading a page triggers compile twice. I'd report an issue. – Pluto

BTW, use the shorter version taskKey to define a new task - lazy val hello = taskKey[Unit]("My custom hello task"). – Pluto

Eventually.... The. New release may fix this – Telespectroscope

Would this same issue cause assets tasks to be compiled twice as well? – Chronicles

Any update? We can observe the same issue (play 2.3.8, sbt 13.7, scala 2.11.5). In our case, the task gets executed over and over again. – Jobholder

I think it should be: lazy val helloTask = TaskKey[Unit]("helloTask", "hello") – Pete

Answer 1

I had the same problem and I found solution.

In Sbt you have three Scopes by configuration axis :

• Compile which defines the main build (src/main/scala).
• Test which defines how to build tests (src/test/scala).
• Runtime which defines the classpath for the run task.

You must use Runtime instead of Compile. It should looks like this:

lazy val helloTask = taskKey[Unit]("hello")

helloTask := println("hello test")

(compile in Runtime) <<= (compile in Runtime) dependsOn helloTask

Highpitched

Answer 2

This was the first result on google so I would like to post my current solution to the problem which actually works with play 2.8 and a multi project build. It is slightly modified. The proposed solution by @bartholomaios results in a compile loop for me.

lazy val helloTask = taskKey[Unit]("hello")
    
helloTask := println("hello test")

lazy val module1: Project = (project in file("modules/module1"))

# Run a task before sbt module1/run
((module1 / run) in Compile) := (((module1 / run) in Compile) dependsOn Compile / helloTask).evaluated

# Run a task before sbt module1/docker:stage
((module1 / stage) in Docker) := (((module1 / stage) in Docker) dependsOn Compile / helloTask).value

Turley