Akka HTTP with Scala.js

This is a Giter8 template showing how you can integrate an Akka HTTP project with a Scala.js project.

Run the application

$ sbt new vmunier/akka-http-scalajs.g8
$ cd akka-http-scalajs
$ sbt
sbt:root> project server
sbt:server> ~reStart
$ open http://localhost:8080

The application contains three directories:

• server Akka HTTP application (server side)
• client Scala.js application (client side)
• shared Scala code that you want to share between the server and the client

Features

The application uses the sbt-web-scalajs sbt plugin.

• compile, run, reStart trigger the Scala.js fastLinkJS task
• ~compile, ~run, ~reStart continuous compilation is also available
• Set scalaJSStage to FullOptStage when packaging your application for fullLinkJS to be executed instead of fastLinkJS:

  sbt 'set Global / scalaJSStage := FullOptStage' Universal/packageBin
  

• Source maps
  • Open your browser dev tool to set breakpoints or to see the guilty line of code when an exception is thrown.
  • Source Maps are enabled in both fastLinkJS and fullLinkJS by default. If you wish to disable Source Maps in fullLinkJS, then add Compile / fullLinkJS / scalaJSLinkerConfig ~= (_.withSourceMap(false)) in the Scala.js projects.

Cleaning

The root project aggregates all the other projects. Use this root project to clean all the projects at once.

$ sbt
sbt:root> clean

Load the server project at sbt startup

Add the following line to build.sbt if you wish to load the server project at sbt startup:

Global / onLoad := (Global / onLoad).value.andThen(state => "project server" :: state)

clean will only delete the server's generated files (in the server/target directory). Call root/clean to delete the generated files for all the projects.

IDE integration

IntelliJ

In IntelliJ, open Project wizard, select Import Project, choose the root folder and click OK. Select Import project from external model option, choose SBT project and click Next. Select additional import options and click Finish. Make sure you use the IntelliJ Scala Plugin v2017.2.7 or higher. There are known issues with prior versions of the plugin.

Eclipse

1. Add addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "5.2.4") to project/plugins.sbt
2. Add the following lines to the server's settings in build.sbt:

// Compile the project before generating Eclipse files, so that generated .scala or .class files for Twirl templates are present
EclipseKeys.preTasks := Seq(Compile / compile)

3. Run $ sbt "eclipse with-source=true"
4. Inside Eclipse, File/Import/General/Existing project..., choose the root folder. Uncheck the third checkbox to only import client, server and shared/.jvm, click Finish.

Classpath during development

The assets (js files, sourcemaps, etc.) are added to the classpath during development thanks to the following lines:

Assets / WebKeys.packagePrefix := "public/",
Runtime / managedClasspath += (Assets / packageBin).value

Note that Assets / packageBin also executes any tasks appended to pipelineStages, e.g. gzip. You may want to avoid executing tasks under pipelineStages during development, because it could take long to execute.

In that case, in order to still have access to the assets under Assets / WebKeys.packagePrefix during development, you can use the following code instead:

lazy val server = project.settings(
...
Assets / WebKeys.packagePrefix := "public/",
Assets / WebKeys.exportedMappings ++= (for ((file, path) <- (Assets / mappings).value)
  yield file -> ((Assets / WebKeys.packagePrefix).value + path)),
...
)