add option to use other renderer easily

src/main/scala/sbtbuildinfo/BuildInfo.scala

@@ -103,7 +103,7 @@ object BuildInfo {
 
     def makeFile(file: File): File = {
       val values = results(keys, options, proj, state)
-      val lines = renderer.header ++ renderer.renderKeys(values) ++ renderer.footer
+      val lines = renderer.renderKeys(values)
       IO.writeLines(file, lines, IO.utf8)
       file
     }

src/main/scala/sbtbuildinfo/BuildInfoKeys.scala

@@ -6,6 +6,7 @@ import Keys._
 trait BuildInfoKeys {
   lazy val buildInfo            = taskKey[Seq[File]]("The task that generates the build info.")
   lazy val buildInfoRenderer    = settingKey[BuildInfoRenderer]("The renderer to use to generate the build info.")
+  lazy val buildInfoRenderFactory = settingKey[BuildInfoRenderer.Factory]("The renderFactory to used to build the renderer.")
   lazy val buildInfoObject      = settingKey[String]("The name for the generated object.")
   lazy val buildInfoPackage     = settingKey[String]("The name for the generated package.")
   lazy val buildInfoUsePackageAsPath = settingKey[Boolean]("If true, the generated object is placed in the folder of the package instead of \"sbt-buildinfo\".")

src/main/scala/sbtbuildinfo/BuildInfoPlugin.scala

@@ -74,7 +74,7 @@ object BuildInfoPlugin extends sbt.AutoPlugin {
     resourceGenerators ++= {
       if(buildInfoRenderer.value.isResource) Seq(buildInfo.taskValue) else Nil
     },
-    buildInfoRenderer := ScalaClassRenderer(
+    buildInfoRenderer := buildInfoRenderFactory.value.apply(
       buildInfoOptions.value,
       buildInfoPackage.value,
       buildInfoObject.value)
@@ -87,6 +87,7 @@ object BuildInfoPlugin extends sbt.AutoPlugin {
     buildInfoUsePackageAsPath := false,
     buildInfoKeys    := Seq(name, version, scalaVersion, sbtVersion),
     buildInfoBuildNumber := buildNumberTask(baseDirectory.value, 1),
-    buildInfoOptions := Seq()
+    buildInfoOptions := Seq(),
+    buildInfoRenderFactory := ScalaCaseObjectRenderer.apply
   )
 }

src/main/scala/sbtbuildinfo/BuildInfoRenderer.scala

@@ -1,12 +1,14 @@
 package sbtbuildinfo
 
+object BuildInfoRenderer {
+  type Factory = (Seq[BuildInfoOption], String, String) => BuildInfoRenderer
+}
+
 trait BuildInfoRenderer {
 
   def fileType: BuildInfoType
   def extension: String
-  def header: Seq[String]
   def renderKeys(infoKeysNameAndValues: Seq[BuildInfoResult]): Seq[String]
-  def footer: Seq[String]
 
   def isSource = fileType == BuildInfoType.Source
   def isResource = fileType == BuildInfoType.Resource

src/main/scala/sbtbuildinfo/ScalaCaseClassRenderer.scala

@@ -0,0 +1,72 @@
+package sbtbuildinfo
+
+case class ScalaCaseClassRenderer(options: Seq[BuildInfoOption], pkg: String, obj: String) extends ScalaRenderer {
+  override def fileType = BuildInfoType.Source
+  override def extension = "scala"
+
+  val traitNames = options.collect{case BuildInfoOption.Traits(ts @ _*) => ts}.flatten
+  val objTraits = if (traitNames.isEmpty) "" else " extends " ++ traitNames.mkString(" with ")
+
+  // It is safe to add `import scala.Predef` even though we need to keep `-Ywarn-unused-import` in mind
+  // because we always generate code that has a reference to `String`. If the "base" generated code were to be
+  // changed and no longer contain a reference to `String`, we would need to remove `import scala.Predef` and
+  // fully qualify every reference. Note it is NOT safe to use `import scala._` because of the possibility of
+  // the project using `-Ywarn-unused-import` because we do not always generated references that are part of
+  // `scala` such as `scala.Option`.
+  def header = List(
+    s"package $pkg",
+    "",
+    "import scala.Predef._",
+    "",
+    s"/** This file was generated by sbt-buildinfo. */"
+  )
+
+  override def renderKeys(buildInfoResults: Seq[BuildInfoResult]) =
+    header ++
+    caseClassDefinitionBegin ++
+      buildInfoResults.flatMap(caseClassParameter).mkString(",\n").split("\n") ++
+      caseClassDefinitionEnd ++
+      toMapMethod(buildInfoResults) ++
+      caseClassEnd ++
+      List("") ++
+      caseObjectLine(buildInfoResults)
+
+  private def caseClassDefinitionBegin = List(
+    s"case class $obj$objTraits("
+  )
+
+  private def caseClassParameter(r: BuildInfoResult): Seq[String] = {
+    val typeDecl = getType(r.typeExpr) getOrElse "Any"
+
+    List(
+      s"  ${r.identifier}: $typeDecl"
+    )
+  }
+
+  private def toMapMethod(results: Seq[BuildInfoResult]) =
+    if (options.contains(BuildInfoOption.ToMap))
+      results
+        .map(result => "    \"%s\" -> %s".format(result.identifier, result.identifier))
+        .mkString("  def toMap: Map[String, Any] = Map[String, Any](\n", ",\n", ")")
+        .split("\n")
+        .toList ::: List("")
+    else Nil
+
+  private def caseClassDefinitionEnd = List(") {", "")
+  private def caseClassEnd = List("}")
+
+  private def caseObjectLine(buildInfoResults: Seq[BuildInfoResult]) = List(
+    s"case object $obj {",
+    s"  val data: $obj = new $obj(${buildInfoResults.map(_.value).map(quote).mkString(",")})",
+    s"}"
+  )
+
+  def toMapLine(results: Seq[BuildInfoResult]): Seq[String] =
+    if (options.contains(BuildInfoOption.ToMap) || options.contains(BuildInfoOption.ToJson))
+      results
+        .map(result => "    \"%s\" -> %s".format(result.identifier, result.identifier))
+        .mkString("  val toMap: Map[String, Any] = Map[String, Any](\n", ",\n", ")")
+        .split("\n")
+        .toList ::: List("")
+    else Nil
+}

src/main/scala/sbtbuildinfo/ScalaCaseObjectRenderer.scala

@@ -0,0 +1,68 @@
+package sbtbuildinfo
+
+private[sbtbuildinfo] case class ScalaCaseObjectRenderer(options: Seq[BuildInfoOption], pkg: String, obj: String) extends ScalaRenderer {
+
+  override def fileType = BuildInfoType.Source
+  override def extension = "scala"
+  val traitNames = options.collect{case BuildInfoOption.Traits(ts @ _*) => ts}.flatten
+  val objTraits = if (traitNames.isEmpty) "" else " extends " ++ traitNames.mkString(" with ")
+
+  // It is safe to add `import scala.Predef` even though we need to keep `-Ywarn-unused-import` in mind
+  // because we always generate code that has a reference to `String`. If the "base" generated code were to be
+  // changed and no longer contain a reference to `String`, we would need to remove `import scala.Predef` and
+  // fully qualify every reference. Note it is NOT safe to use `import scala._` because of the possibility of
+  // the project using `-Ywarn-unused-import` because we do not always generated references that are part of
+  // `scala` such as `scala.Option`.
+  def header = List(
+    s"package $pkg",
+    "",
+    "import scala.Predef._",
+    "",
+    s"/** This object was generated by sbt-buildinfo. */",
+    s"case object $obj$objTraits {"
+  )
+
+  def footer = List("}")
+
+  override def renderKeys(buildInfoResults: Seq[BuildInfoResult]) =
+    header ++
+    buildInfoResults.flatMap(line) ++ Seq(toStringLines(buildInfoResults)) ++
+    toMapLine(buildInfoResults) ++ toJsonLine ++
+    footer
+
+  private def line(result: BuildInfoResult): Seq[String] = {
+    import result._
+    val typeDecl = getType(result.typeExpr) map { ": " + _ } getOrElse ""
+
+    List(
+      s"  /** The value is ${quote(value)}. */",
+      s"  val $identifier$typeDecl = ${quote(value)}"
+    )
+  }
+
+  def toStringLines(results: Seq[BuildInfoResult]): String = {
+    val idents = results.map(_.identifier)
+    val fmt = idents.map("%s: %%s" format _).mkString(", ")
+    val vars = idents.mkString(", ")
+    s"""  override val toString: String = {
+         |    "$fmt" format (
+         |      $vars
+         |    )
+         |  }""".stripMargin
+  }
+
+  def toMapLine(results: Seq[BuildInfoResult]): Seq[String] =
+    if (options.contains(BuildInfoOption.ToMap) || options.contains(BuildInfoOption.ToJson))
+      results
+        .map(result => "    \"%s\" -> %s".format(result.identifier, result.identifier))
+        .mkString("  val toMap: Map[String, Any] = Map[String, Any](\n", ",\n", ")")
+        .split("\n")
+        .toList ::: List("")
+    else Nil
+
+  def toJsonLine: Seq[String] =
+    if (options contains BuildInfoOption.ToJson)
+      List("""  val toJson: String = toMap.map(i => "\"" + i._1 + "\":\"" + i._2 + "\"").mkString("{", ", ", "}")""")
+    else Nil
+
+}

src/main/scala/sbtbuildinfo/ScalaRenderer.scala

@@ -0,0 +1,63 @@
+package sbtbuildinfo
+
+/**
+  * Created by akos on 1/6/17.
+  */
+abstract class ScalaRenderer extends BuildInfoRenderer {
+  protected def getType(typeExpr: TypeExpression): Option[String] = {
+    def tpeToReturnType(tpe: TypeExpression): Option[String] =
+      tpe match {
+        case TypeExpression("Any", Nil)    => None
+        case TypeExpression("Int", Nil)    => Some("scala.Int")
+        case TypeExpression("Long", Nil)   => Some("scala.Long")
+        case TypeExpression("Double", Nil) => Some("scala.Double")
+        case TypeExpression("Boolean", Nil) => Some("scala.Boolean")
+        case TypeExpression("scala.Symbol", Nil) => Some("scala.Symbol")
+        case TypeExpression("java.lang.String", Nil) => Some("String")
+        case TypeExpression("java.net.URL", Nil) => Some("java.net.URL")
+        case TypeExpression("sbt.URL", Nil) => Some("java.net.URL")
+        case TypeExpression("java.io.File", Nil) => Some("java.io.File")
+        case TypeExpression("sbt.File", Nil) => Some("java.io.File")
+        case TypeExpression("scala.xml.NodeSeq", Nil) => Some("scala.xml.NodeSeq")
+
+        case TypeExpression("sbt.ModuleID", Nil) => Some("String")
+        case TypeExpression("sbt.Resolver", Nil) => Some("String")
+
+        case TypeExpression("scala.Option", Seq(arg)) =>
+          tpeToReturnType(arg) map { x => s"scala.Option[$x]" }
+        case TypeExpression("scala.collection.Seq", Seq(arg)) =>
+          tpeToReturnType(arg) map { x => s"scala.collection.Seq[$x]" }
+        case TypeExpression("scala.collection.immutable.Map", Seq(arg0, arg1)) =>
+          for {
+            x0 <- tpeToReturnType(arg0)
+            x1 <- tpeToReturnType(arg1)
+          } yield s"Map[$x0, $x1]"
+        case TypeExpression("scala.Tuple2", Seq(arg0, arg1)) =>
+          for {
+            x0 <- tpeToReturnType(arg0)
+            x1 <- tpeToReturnType(arg1)
+          } yield s"($x0, $x1)"
+        case _ => None
+      }
+    tpeToReturnType(typeExpr)
+  }
+
+  protected def quote(v: Any): String = v match {
+    case x @ ( _: Int | _: Double | _: Boolean | _: Symbol) => x.toString
+    case x: Long            => x.toString + "L"
+    case node: scala.xml.NodeSeq if node.toString().trim.nonEmpty => node.toString()
+    case (k, _v)            => "(%s -> %s)" format(quote(k), quote(_v))
+    case mp: Map[_, _]      => mp.toList.map(quote(_)).mkString("Map(", ", ", ")")
+    case seq: Seq[_]        => seq.map(quote).mkString("scala.collection.Seq(", ", ", ")")
+    case op: Option[_]      => op map { x => "scala.Some(" + quote(x) + ")" } getOrElse {"scala.None"}
+    case url: java.net.URL  => "new java.net.URL(%s)" format quote(url.toString)
+    case file: java.io.File => "new java.io.File(%s)" format quote(file.toString)
+    case s                  => "\"%s\"" format encodeStringLiteral(s.toString)
+  }
+
+  protected def encodeStringLiteral(str: String): String =
+    str.replace("\\","\\\\").replace("\n","\\n").replace("\b","\\b").replace("\r","\\r").
+      replace("\t","\\t").replace("\'","\\'").replace("\f","\\f").replace("\"","\\\"")
+
+
+}