Configure scalafmt and disable scalariform

.scalafmt.conf

@@ -0,0 +1,18 @@
+maxColumn = 100
+project.git = true
+project.excludeFilters = [ /sbt-test/, /input_sources/, /contraband-scala/ ]
+
+# http://docs.scala-lang.org/style/scaladoc.html recommends the JavaDoc style.
+# scala/scala is written that way too https://github.com/scala/scala/blob/v2.12.2/src/library/scala/Predef.scala
+docstrings = JavaDoc
+
+# This also seems more idiomatic to include whitespace in import x.{ yyy }
+spaces.inImportCurlyBraces = true
+
+# This works around sequence wildcard (`_*`) turning into `_ *`
+spaces.beforeSeqWildcard = true
+
+# Vertical alignment only => for pattern matching
+align.tokens.add = [
+  { code = "=>",  owner = "Case"  }
+]

.travis.yml

@@ -5,7 +5,7 @@ scala:
   - 2.12.1
 
 script:
-  - sbt -Dfile.encoding=UTF8 -J-XX:ReservedCodeCacheSize=256M "++$TRAVIS_SCALA_VERSION test"
+  - sbt -Dfile.encoding=UTF8 -J-XX:ReservedCodeCacheSize=256M ";++$TRAVIS_SCALA_VERSION test;scalafmtCheck"
 
 jdk:
   - oraclejdk8

build.sbt

@@ -18,11 +18,19 @@ def commonSettings: Seq[Setting[_]] = Seq(
   scalacOptions += "-Ywarn-unused",
   mimaPreviousArtifacts := Set(), // Some(organization.value %% moduleName.value % "1.0.0"),
   publishArtifact in Compile := true,
-  publishArtifact in Test := false
+  publishArtifact in Test := false,
+  commands += Command.command("scalafmtCheck") { state =>
+    sys.process.Process("git diff --name-only --exit-code").! match {
+      case 0 => // ok
+      case x => sys.error("git diff detected! Did you compile before committing?")
+    }
+    state
+  }
 )
 
 lazy val lmRoot = (project in file(".")).
   aggregate(lm).
+  disablePlugins(com.typesafe.sbt.SbtScalariform).
   settings(
     inThisBuild(Seq(
       homepage := Some(url("https://github.com/sbt/librarymanagement")),
@@ -41,6 +49,7 @@ lazy val lmRoot = (project in file(".")).
   )
 
 lazy val lm = (project in file("librarymanagement")).
+  disablePlugins(com.typesafe.sbt.SbtScalariform).
   settings(
     commonSettings,
     name := "librarymanagement",

project/AutomateScalafmtPlugin.scala

@@ -0,0 +1,66 @@
+import org.scalafmt.bootstrap.ScalafmtBootstrap
+import org.scalafmt.sbt.ScalafmtPlugin
+import sbt._
+import sbt.Keys._
+import sbt.inc.Analysis
+
+// Taken from https://github.com/akka/alpakka/blob/master/project/AutomateScalafmtPlugin.scala
+object AutomateScalafmtPlugin extends AutoPlugin {
+  object autoImport {
+    def automateScalafmtFor(configurations: Configuration*): Seq[Setting[_]] =
+      configurations.flatMap { c =>
+        inConfig(c)(
+          Seq(
+           compileInputs.in(compile) := {
+              scalafmtInc.value
+              compileInputs.in(compile).value
+            },
+            sourceDirectories.in(scalafmtInc) := Seq(scalaSource.value),
+            scalafmtInc := {
+              val cache   = streams.value.cacheDirectory / "scalafmt"
+              val include = includeFilter.in(scalafmtInc).value
+              val exclude = excludeFilter.in(scalafmtInc).value
+              val sources =
+                sourceDirectories
+                  .in(scalafmtInc)
+                  .value
+                  .descendantsExcept(include, exclude)
+                  .get
+                  .toSet
+              def format(handler: Set[File] => Unit, msg: String) = {
+                def update(handler: Set[File] => Unit, msg: String)(in: ChangeReport[File],
+                                                                    out: ChangeReport[File]) = {
+                  val label = Reference.display(thisProjectRef.value)
+                  val files = in.modified -- in.removed
+                  Analysis
+                    .counted("Scala source", "", "s", files.size)
+                    .foreach(count => streams.value.log.info(s"$msg $count in $label ..."))
+                  handler(files)
+                  files
+                }
+                FileFunction.cached(cache)(FilesInfo.hash, FilesInfo.exists)(update(handler, msg))(
+                  sources
+                )
+              }
+              def formattingHandler(files: Set[File]) =
+                if (files.nonEmpty) {
+                  val filesArg = files.map(_.getAbsolutePath).mkString(",")
+                  ScalafmtBootstrap.main(List("--quiet", "-i", "-f", filesArg))
+                }
+              format(formattingHandler, "Formatting")
+              format(_ => (), "Reformatted") // Recalculate the cache
+            }
+          )
+        )
+      }
+  }
+
+  private val scalafmtInc = taskKey[Unit]("Incrementally format modified sources")
+
+  override def requires = ScalafmtPlugin
+
+  override def trigger = allRequirements
+
+  override def projectSettings =
+    (includeFilter.in(scalafmtInc) := "*.scala") +: autoImport.automateScalafmtFor(Compile, Test)
+}

project/plugins.sbt

@@ -2,5 +2,6 @@ addSbtPlugin("org.scala-sbt" % "sbt-houserules" % "0.3.2")
 addSbtPlugin("com.eed3si9n"  % "sbt-doge"       % "0.1.3")
 addSbtPlugin("org.scala-sbt" % "sbt-contraband" % "0.3.0-M4")
 addSbtPlugin("me.lessis"     % "bintray-sbt"    % "0.3.0")
+addSbtPlugin("com.geirsson"  % "sbt-scalafmt"   % "0.6.8")
 
 scalacOptions += "-language:postfixOps"