Generate native-image binaries with sbt

This plugin makes it easy to generate native-image binaries with sbt. Key features:

• automatic GraalVM native-image installation powered by Coursier, no need to start sbt with a custom $JAVA_HOME or spin up Docker. See One-click install for Scala for more details.
• automatic support for Scala 2.12.12+ and 2.13.3+, no need to deal with issues like scala/bug#11634.
• get a notification when the binary is ready to use.
• works on macOS, Windows and Linux.
• works with Java 8 and Java 11.

Overview:

• Getting started
• Configuration
• Generate native-image from GitHub Actions
• Comparison with sbt-native-packager

Getting started

First, add the sbt plugin to your build in project/plugins.sbt.

// project/plugins.sbt
addSbtPlugin("org.scalameta" % "sbt-native-image" % "0.2.1")

Next, enable the plugin to your native-image application in build.sbt and configure the main class.

  // build.sbt
  lazy val myNativeImageProject = project
+   .enablePlugins(NativeImagePlugin)
    .settings(
      // ...
+     Compile / mainClass := Some("com.my.MainClass")
    )

Finally, run the nativeImage task to generate the binary.

$ sbt
> myNativeImageProject/nativeImage
...
[info] Native image ready!
[info] /path/to/your/binary

Optionally, use nativeImageRun to execute the generated binary and manually test that it works as expected.

> myNativeImageProject/nativeImageRun argument1 argument 2
# output from your native-image binary

Configuration

sbt-native-image provides several settings, tasks and input tasks to customize native-image generation and to automate your native-image workflows.

• nativeImage: generate a native image
• nativeImageOptions: customize native image generation
• nativeImageRun: execute the generated native image
• nativeImageCopy: generate a native image and copy the binary
• nativeImageVersion: the GraalVM version to use for native-image
• nativeImageJvm: the GraalVM JVM version to use for native-image
• nativeImageCommand: the command to launch native-image
• nativeImageReady: callback hook when native-image is ready
• nativeImageCoursier: the path to a coursier binary
• nativeImageOutput: the path to the generated native-image binary

nativeImage

Type: TaskKey[File]

Description: runs native-image and returns the resulting binary file.

Example usage: sbt myProject/nativeImage

nativeImageOptions

Type: TaskKey[Seq[String]]

Description: custom native-image linking options. See native-image --help for available options. Empty by default.

Example usage: nativeImageOptions ++= List("--initialize-at-build-time")

nativeImageRun

Type: InputKey[File]

Description: executes the native-image binary with given arguments. This task can only be used after nativeImage has completed.

Example usage:

• sbt myProject/nativeImage 'myProject/nativeImageRun hello'
• Error: sbt clean myProject/nativeImageRun. Crashes because native-image does not exist.

nativeImageCopy

Type: InputKey[File]

Description: identical to nativeImage except the resulting binary is additionally copied to the provided file. This task is helpful when configuring CI to generate the binary in a specific place.

Example usage:

• sbt 'myProject/nativeImageCopy mybinary-x86_64-apple-darwin'.
• sbt 'myProject/nativeImageCopy mybinary-x86_64-pc-linux'.

nativeImageVersion

Type: SettingKey[String]

Description: the GraalVM version to use.

Default: 20.1.0

Example usage: nativeImageVersion := "19.3.3"

nativeImageJvm

Type: SettingKey[String]

Description: the GraalVM JVM version to use.

Default: "graalvm-java11". Must be one of: "graalvm-java11", "graalvm" (Java 8).

Example usage: nativeImageJvm := "graalvm"

nativeImageCommand

Type: TaskKey[Seq[String]]

Description: the base command that is used to launch native-image.

Default: automatically installs GraalVM native-image via Coursier. Customize this setting if you prefer to manually install native-image.

Example usage: nativeImageCommand := List("/path/to/native-image")

nativeImageReady

Type: SettingKey[() => Unit]

Description: a side-effecting callback that is called the native image is ready.

Default: alerts the message "Native image ready!" via the say command-line tool on macOS. Does nothing by default on Linux and Windows.

nativeImageCoursier

Type: TaskKey[File]

Description: the path to a coursier binary.

Default: copies a slim bootstrap binary from sbt-native-image resources. This setting is ignored if you customize nativeImageCommand to use something else than Coursier.

nativeImageOutput

Type: SettingKey[File]

Description: the path to the native-image binary that is generated.

Default: target/native-image/NAME where NAME is the name of the sbt project. for available options.

Example usage: nativeImageOutput := file("target") / "my-binary"

Generate native-image from GitHub Actions

The easiest way to distribute native-image binaries for Linux and macOS is to build the binaries in CI with GitHub Actions.

1. Copy the native.yml file from this repo into the .github/workflows/ directory in your project.

   mkdir -p .github/workflows && \
     curl -L https://raw.githubusercontent.com/scalameta/sbt-native-image/master/.github/workflows/native.yml > .github/workflows/native.yml
   

2. Edit the file to replace "example" with the name of your binary.

3. Commit your changes.

4. Push your commit to GitHub and see the binary get uploaded as an artifact to the CI job.

5. Create a GitHub release and see the binary get uploaded as assets to the release page.

Comparison with sbt-native-packager

The sbt-native-packager plugin provides similar support to generate native-image binaries. Check out their documentation at https://sbt-native-packager.readthedocs.io/en/stable/formats/graalvm-native-image.html

The key differences between sbt-native-packager and sbt-native-image are:

• sbt-native-image automatically installs GraalVM native-image by default. You don't need to configure a docker image or manually install a correct GraalVM JDK before starting sbt.
• sbt-native-image automatically works out-of-the-box with Scala 2.12.12+ and 2.13.3+. You don't need custom settings to work around issues like like scala/bug#11634.
• sbt-native-image displays live progress output from the native-image while it's generating the binary. For some reason, sbt-native-packager only displays output from native-image after the process completes (see issue #1345).
• sbt-native-packager has Docker support, which is helpful if you need more fine-grained control over the linking environment. There are no plans to add Docker support in sbt-native-image.