1 files changed, 82 insertions, 0 deletions
diff --git a/src/main/scala/xyz.driver.sbt/Linting.scala b/src/main/scala/xyz.driver.sbt/Linting.scala
new file mode 100644
index 0000000..8a293b6
--- /dev/null
+++ b/src/main/scala/xyz.driver.sbt/Linting.scala
@@ -0,0 +1,82 @@
+package xyz.driver.sbt
+
+import com.lucidchart.sbt.scalafmt.ScalafmtCorePlugin.autoImport.{scalafmtConfig, _}
+import com.lucidchart.sbt.scalafmt.ScalafmtPlugin
+import org.scalastyle.sbt.ScalastylePlugin
+import org.scalastyle.sbt.ScalastylePlugin.autoImport.{scalastyle, scalastyleConfig}
+import sbt.Keys._
+import sbt._
+
+import scala.collection.JavaConverters._
+
+/** Enforces common formatting and catches compiler warnings. */
+object Linting extends AutoPlugin {
+
+  override def requires = ScalafmtPlugin && ScalastylePlugin
+  override def trigger  = allRequirements
+
+  lazy val formatSettings: Seq[Def.Setting[_]] = Seq(
+    scalafmtConfig := {
+      val packaged = getClass.getClassLoader.getResourceAsStream("scalafmt.conf")
+      val out      = file(".scalafmt.conf")
+      IO.write(out, IO.readBytes(packaged))
+      out
+    },
+    scalafmtTestOnCompile in Test := true
+  )
+
+  lazy val scalastyleSettings: Seq[Def.Setting[_]] = Seq(
+    scalastyleConfig := {
+      val stream = getClass.getClassLoader.getResourceAsStream("scalastyle-config.xml")
+      val out    = file(".scalastyle-config.xml")
+      IO.write(out, IO.readBytes(stream))
+      out
+    },
+    test in Test := (test in Test).dependsOn((scalastyle in Test).toTask("")).value
+  )
+
+  lazy val scalacSettings: Seq[Def.Setting[_]] = Seq(
+    scalacOptions in Compile ++= Seq(
+      "-language:higherKinds",
+      "-language:implicitConversions",
+      "-language:postfixOps",
+      "-language:reflectiveCalls", // TODO this should be discouraged
+      "-unchecked",
+      "-deprecation",
+      "-feature",
+      "-encoding",
+      "utf8",
+      "-Xlint:_,-unused,-missing-interpolator",
+      "-Ywarn-numeric-widen",
+      "-Ywarn-dead-code",
+      "-Ywarn-unused:_,-explicits,-implicits"
+    ),
+    // Currently, scalac does not provide a way to fine-tune the treating of
+    // warnings as errors. Either all are considered errors
+    // (with -Xfatal-warnings), or none are. This hack analyzes the compiler's
+    // output and treats all warnings as errors, except for deprecations.
+    compile in Compile := {
+      val log      = streams.value.log
+      val compiled = (compile in Compile).value
+      val problems = compiled.readSourceInfos().getAllSourceInfos.asScala.flatMap {
+        case (_, info) => info.getReportedProblems
+      }
+      var deprecationsOnly = true
+      problems.foreach { problem =>
+        if (!problem.message().contains("is deprecated")) {
+          deprecationsOnly = false
+          log.error(s"[fatal warning] ${problem.message()}")
+        }
+      }
+      if (!deprecationsOnly)
+        throw new FatalWarningsException("Fatal warnings: some warnings other than deprecations were found.")
+      compiled
+    }
+  )
+
+  lazy val lintSettings = formatSettings ++ scalastyleSettings ++ scalacSettings
+
+  override def projectSettings: Seq[Def.Setting[_]] = inConfig(Compile)(lintSettings) ++ inConfig(Test)(lintSettings)
+
+}
+case class FatalWarningsException(message: String) extends Exception(message)