Use a macro to create StringTypeTag instances

Using the scala reflect library always introduces significant
classloading overhead. We can eliminate the classloading overhead by
generating StringTypeTags at compile time instead.

This sped up average project loading time by a few hundred milliseconds
on my computer. The ManagedLoggedReporter in zinc is still using the
type tag based apis but after the next sbt release, we can upgrade the
zinc apis. We also could consider breaking binary compatibility.

build.sbt

@@ -359,7 +359,7 @@ lazy val utilPosition = (project in file("internal") / "util-position")
 
 lazy val utilLogging = (project in file("internal") / "util-logging")
   .enablePlugins(ContrabandPlugin, JsonCodecPlugin)
-  .dependsOn(utilInterface, collectionProj)
+  .dependsOn(utilInterface, collectionProj, coreMacrosProj)
   .settings(
     utilCommonSettings,
     name := "Util Logging",
@@ -781,7 +781,7 @@ lazy val commandProj = (project in file("main-command"))
 lazy val coreMacrosProj = (project in file("core-macros"))
   .dependsOn(collectionProj)
   .settings(
-    baseSettings,
+    baseSettings :+ (crossScalaVersions := (scala212 :: scala213 :: Nil)),
     name := "Core Macros",
     libraryDependencies += "org.scala-lang" % "scala-compiler" % scalaVersion.value,
     mimaSettings,

core-macros/src/main/scala/sbt/internal/util/appmacro/StringTypeTag.scala

@@ -0,0 +1,27 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt.internal.util.appmacro
+
+import scala.reflect.macros.blackbox
+
+object StringTypeTag {
+  def impl[A: c.WeakTypeTag](c: blackbox.Context): c.Tree = {
+    import c.universe._
+    val tpe = weakTypeOf[A]
+    def typeToString(tpe: Type): String = tpe match {
+      case TypeRef(_, sym, args) if args.nonEmpty =>
+        val typeCon = tpe.typeSymbol.fullName
+        val typeArgs = args map typeToString
+        s"""$typeCon[${typeArgs.mkString(",")}]"""
+      case _ => tpe.toString
+    }
+
+    val key = Literal(Constant(typeToString(tpe)))
+    q"new sbt.internal.util.StringTypeTag[$tpe]($key)"
+  }
+}

internal/util-logging/src/main/scala/sbt/internal/util/ManagedLogger.scala

@@ -7,12 +7,12 @@
 
 package sbt.internal.util
 
-import sbt.util._
 import org.apache.logging.log4j.{ Logger => XLogger }
 import org.apache.logging.log4j.message.ObjectMessage
-import sjsonnew.JsonFormat
-import scala.reflect.runtime.universe.TypeTag
 import sbt.internal.util.codec.JsonProtocol._
+import sbt.util._
+import scala.reflect.runtime.universe.TypeTag
+import sjsonnew.JsonFormat
 
 /**
  * Delegates log events to the associated LogExchange.
@@ -35,29 +35,53 @@ class ManagedLogger(
     )
   }
 
-  private lazy val SuccessEventTag = scala.reflect.runtime.universe.typeTag[SuccessEvent]
   // send special event for success since it's not a real log level
   override def success(message: => String): Unit = {
     if (terminal.fold(true)(_.isSuccessEnabled)) {
       infoEvent[SuccessEvent](SuccessEvent(message))(
         implicitly[JsonFormat[SuccessEvent]],
-        SuccessEventTag
+        StringTypeTag.fast[SuccessEvent],
       )
     }
   }
 
-  def registerStringCodec[A: ShowLines: TypeTag]: Unit = {
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  def registerStringCodec[A](
+      s: ShowLines[A],
+      tt: scala.reflect.runtime.universe.TypeTag[A]
+  ): Unit = {
+    LogExchange.registerStringCodec[A](s, tt)
+  }
+  def registerStringCodec[A: ShowLines: StringTypeTag]: Unit = {
     LogExchange.registerStringCodec[A]
   }
 
-  final def debugEvent[A: JsonFormat: TypeTag](event: => A): Unit = logEvent(Level.Debug, event)
-  final def infoEvent[A: JsonFormat: TypeTag](event: => A): Unit = logEvent(Level.Info, event)
-  final def warnEvent[A: JsonFormat: TypeTag](event: => A): Unit = logEvent(Level.Warn, event)
-  final def errorEvent[A: JsonFormat: TypeTag](event: => A): Unit = logEvent(Level.Error, event)
-  def logEvent[A: JsonFormat: TypeTag](level: Level.Value, event: => A): Unit = {
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  final def debugEvent[A](event: => A, f: JsonFormat[A], t: TypeTag[A]): Unit =
+    debugEvent(event)(f, StringTypeTag.apply(t))
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  final def infoEvent[A](event: => A, f: JsonFormat[A], t: TypeTag[A]): Unit =
+    infoEvent(event)(f, StringTypeTag.apply(t))
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  final def warnEvent[A](event: => A, f: JsonFormat[A], t: TypeTag[A]): Unit =
+    warnEvent(event)(f, StringTypeTag.apply(t))
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  final def errorEvent[A](event: => A, f: JsonFormat[A], t: TypeTag[A]): Unit =
+    errorEvent(event)(f, StringTypeTag.apply(t))
+
+  final def debugEvent[A: JsonFormat: StringTypeTag](event: => A): Unit =
+    logEvent(Level.Debug, event)
+  final def infoEvent[A: JsonFormat: StringTypeTag](event: => A): Unit = logEvent(Level.Info, event)
+  final def warnEvent[A: JsonFormat: StringTypeTag](event: => A): Unit = logEvent(Level.Warn, event)
+  final def errorEvent[A: JsonFormat: StringTypeTag](event: => A): Unit =
+    logEvent(Level.Error, event)
+  @deprecated("Use macro-powered StringTypeTag.fast instead", "1.4.0")
+  def logEvent[A](level: Level.Value, event: => A, f: JsonFormat[A], t: TypeTag[A]): Unit =
+    logEvent(level, event)(f, StringTypeTag.apply(t))
+  def logEvent[A: JsonFormat](level: Level.Value, event: => A)(
+      implicit tag: StringTypeTag[A]
+  ): Unit = {
     val v: A = event
-    val tag = StringTypeTag[A]
-    LogExchange.getOrElseUpdateJsonCodec(tag.key, implicitly[JsonFormat[A]])
     // println("logEvent " + tag.key)
     val entry: ObjectEvent[A] = ObjectEvent(level, v, channelName, execId, tag.key)
     xlogger.log(

internal/util-logging/src/main/scala/sbt/internal/util/StringTypeTag.scala

@@ -7,6 +7,7 @@
 
 package sbt.internal.util
 
+import scala.language.experimental.macros
 import scala.reflect.runtime.universe._
 
 /** This is used to carry type information in JSON. */
@@ -15,6 +16,10 @@ final case class StringTypeTag[A](key: String) {
 }
 
 object StringTypeTag {
+
+  /** Generates a StringTypeTag for any type at compile time. */
+  implicit def fast[A]: StringTypeTag[A] = macro appmacro.StringTypeTag.impl[A]
+  @deprecated("Prefer macro generated StringTypeTag", "1.4.0")
   def apply[A: TypeTag]: StringTypeTag[A] =
     synchronized {
       def doApply: StringTypeTag[A] = {
@@ -38,6 +43,7 @@ object StringTypeTag {
       retry(3)
     }
 
+  @deprecated("Prefer macro generated StringTypeTag", "1.4.0")
   def typeToString(tpe: Type): String =
     tpe match {
       case TypeRef(_, sym, args) =>

internal/util-logging/src/main/scala/sbt/util/LogExchange.scala

@@ -15,7 +15,6 @@ import org.apache.logging.log4j.core.config.{ AppenderRef, LoggerConfig }
 import org.apache.logging.log4j.core.layout.PatternLayout
 import scala.collection.JavaConverters._
 import scala.collection.concurrent
-import scala.reflect.runtime.universe.TypeTag
 import sjsonnew.JsonFormat
 
 // http://logging.apache.org/log4j/2.x/manual/customconfig.html
@@ -114,9 +113,15 @@ sealed abstract class LogExchange {
   def getOrElseUpdateStringCodec[A](tag: String, v: ShowLines[A]): ShowLines[A] =
     stringCodecs.getOrElseUpdate(tag, v).asInstanceOf[ShowLines[A]]
 
-  def registerStringCodec[A: ShowLines: TypeTag]: Unit = {
-    val tag = StringTypeTag[A]
-    registerStringCodecByStringTypeTag(tag)
+  @deprecated("Prefer macro based registerStringCodec", "1.4.0")
+  def registerStringCodec[A](
+      st: ShowLines[A],
+      tt: scala.reflect.runtime.universe.TypeTag[A]
+  ): Unit = {
+    registerStringCodecByStringTypeTag(StringTypeTag.apply[A](tt))(st)
+  }
+  private[sbt] def registerStringCodec[A: ShowLines: StringTypeTag]: Unit = {
+    registerStringCodecByStringTypeTag(implicitly[StringTypeTag[A]])
   }
 
   private[sbt] def registerStringCodecByStringTypeTag[A: ShowLines](tag: StringTypeTag[A]): Unit = {

internal/util-logging/src/test/scala/LogExchangeSpec.scala

@@ -14,9 +14,17 @@ import org.scalatest._
 class LogExchangeSpec extends FlatSpec with Matchers {
   import LogExchange._
 
-  checkTypeTag("stringTypeTagThrowable", stringTypeTagThrowable, StringTypeTag[Throwable])
-  checkTypeTag("stringTypeTagTraceEvent", stringTypeTagTraceEvent, StringTypeTag[TraceEvent])
-  checkTypeTag("stringTypeTagSuccessEvent", stringTypeTagSuccessEvent, StringTypeTag[SuccessEvent])
+  checkTypeTag("stringTypeTagThrowable", stringTypeTagThrowable, StringTypeTag.fast[Throwable])
+  checkTypeTag(
+    "stringTypeTagTraceEvent",
+    stringTypeTagTraceEvent,
+    StringTypeTag.fast[TraceEvent]
+  )
+  checkTypeTag(
+    "stringTypeTagSuccessEvent",
+    stringTypeTagSuccessEvent,
+    StringTypeTag.fast[SuccessEvent]
+  )
 
   private def checkTypeTag[A](name: String, inc: StringTypeTag[A], exp: StringTypeTag[A]): Unit =
     s"LogExchange.$name" should s"match real StringTypeTag[$exp]" in {

internal/util-logging/src/test/scala/ManagedLoggerSpec.scala

@@ -84,7 +84,7 @@ class ManagedLoggerSpec extends FlatSpec with Matchers {
     } {
       pool.submit(new Runnable {
         def run(): Unit = {
-          val stringTypeTag = StringTypeTag[List[Int]]
+          val stringTypeTag = StringTypeTag.fast[List[Int]]
           val log = LogExchange.logger(s"foo$i")
           LogExchange.bindLoggerAppenders(s"foo$i", List(LogExchange.asyncStdout -> Level.Info))
           if (i % 100 == 0) {

main/src/main/scala/sbt/internal/XMainConfiguration.scala

@@ -14,7 +14,6 @@ import java.util.concurrent.{ ExecutorService, Executors }
 import ClassLoaderClose.close
 
 import sbt.plugins.{ CorePlugin, IvyPlugin, JvmPlugin }
-import sbt.util.LogExchange
 import xsbti._
 
 private[internal] object ClassLoaderWarmup {
@@ -29,7 +28,6 @@ private[internal] object ClassLoaderWarmup {
         ()
       }
 
-      submit(LogExchange.context)
       submit(Class.forName("sbt.internal.parser.SbtParserInit").getConstructor().newInstance())
       submit(CorePlugin.projectSettings)
       submit(IvyPlugin.projectSettings)

main/src/main/scala/sbt/internal/server/BuildServerReporter.scala

@@ -11,7 +11,7 @@ import java.io.File
 
 import sbt.StandardMain
 import sbt.internal.bsp._
-import sbt.internal.inc.ManagedLoggedReporter
+import sbt.internal.inc.LoggedReporter
 import sbt.internal.util.ManagedLogger
 import xsbti.{ Problem, Severity, Position => XPosition }
 
@@ -30,7 +30,11 @@ class BuildServerReporter(
     logger: ManagedLogger,
     sourcePositionMapper: XPosition => XPosition = identity[XPosition],
     sources: Seq[File]
-) extends ManagedLoggedReporter(maximumErrors, logger, sourcePositionMapper) {
+) extends LoggedReporter(maximumErrors, logger, sourcePositionMapper) {
+  import LoggedReporter.problemFormats._
+  import LoggedReporter.problemStringFormats._
+  logger.registerStringCodec[Problem]
+
   import sbt.internal.bsp.codec.JsonProtocol._
   import sbt.internal.inc.JavaInterfaceUtil._
 
@@ -55,21 +59,21 @@ class BuildServerReporter(
     publishDiagnostic(problem)
 
     // console channel can keep using the xsbi.Problem
-    super.logError(problem)
+    logger.errorEvent(problem)
   }
 
   override def logWarning(problem: Problem): Unit = {
     publishDiagnostic(problem)
 
     // console channel can keep using the xsbi.Problem
-    super.logWarning(problem)
+    logger.warnEvent(problem)
   }
 
   override def logInfo(problem: Problem): Unit = {
     publishDiagnostic(problem)
 
     // console channel can keep using the xsbi.Problem
-    super.logInfo(problem)
+    logger.infoEvent(problem)
   }
 
   private def publishDiagnostic(problem: Problem): Unit = {