SBT Cookbook

Hook actions around play run

You can apply actions around the play run command by extending PlayRunHook. This trait define the following methods:

• beforeStarted(): Unit
• afterStarted(addr: InetSocketAddress): Unit
• afterStopped(): Unit

beforeStarted method is called before the play application is started, but after all “before run” tasks have been completed.

afterStarted method is called after the play application has been started.

afterStopped method is called after the play process has been stopped.

Note: The following example illustrate how you can start and stop a command with play run hook. In the near future sbt-web will provide a better way to integrate Grunt with an SBT build.

Now let’s say you want to build a Web application with grunt before the application is started. First, you need to create a Scala object in the project/ directory to extend PlayRunHook. Let’s name it Grunt.scala:

import play.PlayRunHook
import sbt._

object Grunt {
  def apply(base: File): PlayRunHook = {

    object GruntProcess extends PlayRunHook {

      override def beforeStarted(): Unit = {
        Process("grunt dist", base).run
      }
    }

    GruntProcess
  }
}

Then in the build.sbt file you need to register this hook:

import Grunt._
import play.PlayImport.PlayKeys.playRunHooks

playRunHooks <+= baseDirectory.map(base => Grunt(base))

This will execute the grunt dist command in baseDirectory before the application is started.

Now we want to execute grunt watch command to observe changes and rebuild the Web application when that happen:

import play.PlayRunHook
import sbt._

import java.net.InetSocketAddress

object Grunt {
  def apply(base: File): PlayRunHook = {

    object GruntProcess extends PlayRunHook {

      var process: Option[Process] = None

      override def beforeStarted(): Unit = {
        Process("grunt dist", base).run
      }

      override def afterStarted(addr: InetSocketAddress): Unit = {
        process = Some(Process("grunt watch", base).run)
      }

      override def afterStopped(): Unit = {
        process.map(p => p.destroy())
        process = None
      }
    }

    GruntProcess
  }
}

Once the application has been started we execute grunt watch and when the application has been stopped we destroy the grunt process. There’s nothing to change in build.sbt

Add compiler options

For example, you may want to add the feature flag to have details on feature warnings:

[info] Compiling 1 Scala source to ~/target/scala-2.10/classes...
[warn] there were 1 feature warnings; re-run with -feature for details

Simply add -feature to the scalacOptions attribute:

scalacOptions += "-feature"

Add additional asset directory

For example you can add the pictures folder to be included as an additional asset directory:

unmanagedResourceDirectories in Assets <+= baseDirectory { _ / "pictures" }

This will allow you to use routes.Assets.at with this folder.

Disable documentation

To speed up compilation you can disable documentation generation:

sources in (Compile, doc) := Seq.empty

publishArtifact in (Compile, packageDoc) := false

The first line will disable documentation generation and the second one will avoid to publish the documentation artifact.

Configure ivy logging level

By default ivyLoggingLevel is set on UpdateLogging.DownloadOnly. You can change this value with:

• UpdateLogging.Quiet only displays errors
• UpdateLogging.FULL logs the most

For example if you want to only display errors:

ivyLoggingLevel := UpdateLogging.Quiet

Fork and parallel execution in test

By default parallel execution is disabled and fork is enabled. You can change this behavior by setting parallelExecution in Test and/or fork in Test:

parallelExecution in Test := true

fork in Test := false