sbt-web-scalajs

sbt-web-scalajs is a SBT plugin which allows you to use Scala.js along with any sbt-web server. It uses the sbt-web and scala-js plugins.

Setup

Specify the sbt version in project/build.properties, which needs to be 0.13.16 or higher (or sbt 1.x):

sbt.version=1.1.6

If you want to use Scala.js 1.x, add the following plugins to project/plugins.sbt:

addSbtPlugin("com.vmunier" % "sbt-web-scalajs" % "1.0.9")
addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.0.0-M7")

Otherwise, if you prefer using Scala.js 0.6.x, add the following plugins to project/plugins.sbt:

addSbtPlugin("com.vmunier" % "sbt-web-scalajs" % "1.0.9-0.6")
addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.27")

Lastly, put the following configuration in build.sbt:

lazy val server = project.settings(
  scalaJSProjects := Seq(client),
  pipelineStages in Assets := Seq(scalaJSPipeline)
).enablePlugins(SbtWeb)

lazy val client = project.enablePlugins(ScalaJSPlugin, ScalaJSWeb)

Note: make sure you use the Assets scope.

Examples

To see the plugin in action, you can run sbt new with one of these Giter8 templates:

Play with Scala.js: sbt new vmunier/play-scalajs.g8
Akka HTTP with Scala.js: sbt new vmunier/akka-http-scalajs.g8

Selecting fastOptJS or fullOptJS

sbt-web-scalajs maintains a list of dev commands, which includes run, compile and re-start (show scalaJSPipeline::devCommands to see the full list). When one of the dev commands is executed in SBT, e.g. sbt run, sbt-web-scalajs considers to be in development mode and will call Scala.js fastOptJS. For all other commands, which are not listed in the devCommands setting, e.g. sbt universal:packageBin, sbt-web-scalajs considers to be in production mode and will call Scala.js fullOptJS.

It is possible to control when fastOptJS or fullOptJS is selected, either by extending the devCommands setting or by overriding the isDevMode task.

Extending `devCommands`

You may want to instruct sbt-web-scalajs to execute fastOptJS when the tests are run, in which case you can add devCommands in scalaJSPipeline ++= Seq("test", "testOnly") to your server's build settings.

Overriding `isDevMode`

You can also explicitly control when fastOptJS or fullOptJS is executed. For example, you may want sbt-web-scalajs to always execute fastOptJS, except when a SCALAJS_PROD environment variable is defined, in which case add isDevMode in scalaJSPipeline := !sys.env.get("SCALAJS_PROD").isDefined to your server's build settings. Simply start SBT with sbt and fastOptJS will be executed for any command; similarly start SBT with SCALAJS_PROD=true sbt and fullOptJS will be executed for any command.

How it works

There are two plugins: WebScalaJS and ScalaJSWeb.

WebScalaJS is automatically added to your SbtWeb project.
ScalaJSWeb should be manually added to the Scala.js projects that you want to connect the source mapping to your SbtWeb project.
Scala.js projects are collected in the scalaJSProjects setting key of the SbtWeb project. The plugin does nothing if scalaJSProjects is not specified or is empty.
When compilation or testing takes place, then the WebScalaJS plugin runs all required tasks on scalaJSProjects projects, copies the output to SbtWeb assets and takes care about source maps.

Settings and Tasks

scalaJSProjects setting lists the Scala.js projects whose output is used by the server.
scalaJSDev task runs all tasks for development, including Scala.js fastOptJS task and source maps.
scalaJSProd task runs all tasks for production, including Scala.js fullOptJS task and source maps.
scalaJSPipeline task runs scalaJSDev when isDevMode is true, runs scalaJSProd otherwise.
isDevMode task returns true if the sbt command run by the user exists in the devCommands setting. Some users may want to override isDevMode to read the dev/prod mode from a configuration file or from an environment variable.
devCommands setting contains the name of the commands used during development, which includes run, compile and re-start. It can be extended/overridden to contain different dev commands. For example, adding devCommands in scalaJSPipeline ++= Seq("test", "testOnly") to your build would make scalaJSPipeline trigger scalaJSDev instead of scalaJSProd when running tests.

Source Maps

The plugin copies the Scala files to the SbtWeb assets, so that they can be served to the browser and used for Source Maps.

Source Map and Scala files do not exist in production by default to prevent your users from seeing the source files. But it can easily be enabled in production too by setting scalaJSLinkerConfig in fullOptJS ~= (_.withSourceMap(true)) in the Scala.js projects.

Scala.js continuous compilation

The plugin also watches files from the Scala.js projects. Redefine compile to trigger scalaJSPipeline when using compile, ~compile, ~run:

compile in Compile := ((compile in Compile) dependsOn scalaJSPipeline.map(f => f(Seq.empty))).value

As we only care about triggering scalaJSPipeline dependencies here, the line can be shortened to:

compile in Compile := ((compile in Compile) dependsOn scalaJSPipeline).value

Publish a new version of the plugin

For Scala.js 0.6.x:

$ sbt ^publish

For Scala.js 1.x:

$ SCALAJS_VERSION=1.0.0-RC1 sbt ^publish

FabioPinheiro/sbt-web-scalajs