It is a sad state of affairs that this feels necessary, but I ask that if you support or are planning to vote for the reelection of the 45th president of the United States of America, that you not use this plugin.

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A collection of sbt plugins for formatting source files. The current version of the plugin is compatible with sbt 1.3.0 and greater. The legacy version, 0.1.6, works with sbt 1.x and sbt 0.13.x.

There are four plugins in the family:

  1. sbt-clang-format formats c family languages (c/c++/objc) using clang-format.
  2. sbt-java-format formats java source code using google java formater.
  3. sbt-scala-format formats scala source code using scalafmt.
  4. sbt-source-format aggregates the first three plugins.
  5. sbt-jvm-format aggregates (2) and (3) and provides keys for formatting all of the java and scala sources (including sbt build files).

The latest version is 0.3.1. To use the plugin, add one or more of

addSbtPlugin("com.swoval" % "sbt-clang-format" % "0.3.1")
addSbtPlugin("com.swoval" % "sbt-java-format" % "0.3.1")
addSbtPlugin("com.swoval" % "sbt-jvm-format" % "0.3.1")
addSbtPlugin("com.swoval" % "sbt-scala-format" % "0.3.1")
addSbtPlugin("com.swoval" % "sbt-source-format" % "0.3.1")

to your project/plugins.sbt file.


Each format plugin provides two tasks: one for formatting a source file and overwriting its contents if they differ and one for checking that the formatting is correct without overwriting. In the case of sbt-clang-format, the format task is clangfmt and the check task is clangfmtCheck. Similarly, the scala and java plugins provide scalafmt, scalafmtCheck, javafmt and javafmtCheck. When using sbt-jvm-format, in addition to javafmt, scalafmt, etc, there is also jvmfmt, which formats all of the java and scala sources in the project for a configuration. The jvmfmtAll task formats all of the java and scala sources in the Compile and Test tasks as well as the scala and java sources that comprise the project sbt build.

Formatting is incremental. The plugin will only attempt to format files that have not been previously formatted or verified as formatted. It also fully interoperates with the ~ command. For example, running ~javafmt, sbt will watch for all of the "*.java" files and reformat whenever any are modified.

Source files

By default the javafmt source files will be all of the files ending with *.java in the unmanagedSourceDirectories. The javafmt task is defined both in the Compile and Test configurations as well as in the project configuration. Running javafmt will format all of the java source files in the project while running Test / javafmt or Compile / javafmt will only format the sources in the respective configurations.

For clangfmt no default sources are specified. Add *.c sources with:

clangfmt / fileInputs += baseDirectory.value.toGlob / "src" / ** / "*.c"

Sources can also be added to javafmt and scalafmt using fileInputs in the appropriate configs, e.g.

Compile / scalafmt / fileInputs += baseDirectory.value.toGlob / "other" / ** / "*.scala"

Custom formatters

The plugin also provides a library for defining a custom formatter for any source file type. To create a custom formatter, add

libraryDependencies += "com.swoval" %% "sbt-source-format-lib" % "0.2.3"

to project/plugins.sbt (or build.sbt for a plugin).

A no-op javascript formatter can be added to a build.sbt file like so:

import com.swoval.format.lib.SourceFormat
import java.nio.file.Files

val jsfmt = taskKey[Unit]("Format js files.")
  (path, logger) => new String(Files.readAllBytes(path)),
  Def.setting(sourceDirectory.value.toGlob / ** / "*.js" :: Nil)


In order to use the clangfmt command, the clang-format utility must be installed. On osx, it can be installed using homebrew: brew install clang-format. On linux, it can be installed with apt: apt-get install clang-format (sudo is probably necessary on most setups).