An sbt plugin to format your Scala sources with Scalariform
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An sbt plugin to format your Scala source files with Scalariform.

How to use

Declaring the plugin

This is done in project/plugins/Plugins.scala:

import sbt._

class Plugins(info: ProjectInfo) extends PluginDefinition(info) {
  val formatter = "com.github.olim7t" % "sbt-scalariform" % "1.0.3"

Configuring a simple project

Mix the ScalariformPlugin trait into your project definition and customize the formatting options if necessary:

import sbt._
import com.github.olim7t.sbtscalariform._

class MySbtProject(info: ProjectInfo) extends DefaultProject(info) with ScalariformPlugin {
  // See ScalariformOptions.scala and the Scalariform documentation for the list of options.
  // NB: InPlace is assumed unless Test is specified
  override def scalariformOptions = Seq(VerboseScalariform)

This will by default format all your main and test sources before each compilation.

Disabling automatic formatting

  override def formatBeforeCompiling = false

The formatting actions still exist, but are not run automatically. You need to run format-sources or test-format-sources manually from the sbt prompt.

Disabling formatting

You can override formatSourcesAction or testFormatSourcesAction to completely remove the corresponding action. A typical scenario is when you keep automatic mode, but don't want to format the test sources:

  override def testFormatSourcesAction = task { None }

Using specific options for test sources

  override def scalariformTestOptions = Seq(PreserveSpaceBeforeArguments(true))

Specifying the sources' encoding

The default is UTF-8.

  override def scalaSourcesEncoding = "ISO-8859-1"

Controlling failure behavior

By default, a Scalariform failure does not abort the whole build: the error is logged, the files that couldn't be formatted are left as-is, and the build proceeds to compilation. There are two reasons for this:

  • in the event of a Scalariform bug, valid Scala code should not be prevented from compiling;
  • if the error is a genuine Scala error, the Scala compiler currently provides better error messages.

To override this behavior:

  // Abort the build if Scalariform fails:
  override def failOnFormattingError = true

Configuring a multi-module project

Declare the plugin for the parent project. Mix the trait into the definitions of the sub-modules that you want to format; you can create an intermediary trait to factor the formatting options. Scalariform itself uses this setup: see here.


From sbt, reload your project definition by running reload (or just launch sbt if you were not already in interactive mode). This will also download and compile the plugin.

Your project now has two new actions: format-sources and test-format-sources, which get run automatically before compile and test-compile respectively.

How it works

For each type of sources (main, test), the plugin uses a timestamp file in the target directory to detect which files have changed, and therefore need to be reformatted.

The plugin forks a new VM to invoke Scalariform; this is required, since sbt project definitions are compiled against Scala 2.7.7, while Scalariform uses 2.8.0. The list of files to format is passed through a temporary file (fed to Scalariform's -l option).

Building from source

If you want to try the latest features, or just hack on the plugin, here is the procedure to build it locally:

git clone git://
cd sbt-scalariform
# From the sbt prompt:
# ... downloads Scalariform ...

If you repeatedly deploy and test the same version of the plugin, remember to run ;clean-plugins ;reload in the target project(s).