Filter out log events more aggressively

As per sbt/sbt#3711 this was identified as a
performance hotspot.

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

@@ -1,9 +1,10 @@
 package sbt.internal.util
 
-import sbt.util._
+import sbt.util.{ Level, _ }
 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._
 
@@ -19,10 +20,12 @@ class ManagedLogger(
   override def trace(t: => Throwable): Unit =
     logEvent(Level.Error, TraceEvent("Error", t, channelName, execId))
   override def log(level: Level.Value, message: => String): Unit = {
-    xlogger.log(
-      ConsoleAppender.toXLevel(level),
-      new ObjectMessage(StringEvent(level.toString, message, channelName, execId))
-    )
+    if (shouldLog(level)) {
+      xlogger.log(
+        ConsoleAppender.toXLevel(level),
+        new ObjectMessage(StringEvent(level.toString, message, channelName, execId))
+      )
+    }
   }
 
   // send special event for success since it's not a real log level
@@ -38,18 +41,24 @@ class ManagedLogger(
   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 = {
-    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(
-      ConsoleAppender.toXLevel(level),
-      new ObjectMessage(entry)
-    )
+    if (shouldLog(level)) {
+      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(
+        ConsoleAppender.toXLevel(level),
+        new ObjectMessage(entry)
+      )
+    }
   }
 
+  private def shouldLog(level: Level.Value) =
+    xlogger.getLevel.isMoreSpecificThan(ConsoleAppender.toXLevel(level))
+
   @deprecated("No longer used.", "1.0.0")
   override def ansiCodesSupported = ConsoleAppender.formatEnabledInEnv
 }

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

@@ -17,9 +17,9 @@ abstract class AbstractLogger extends Logger {
   /** Defined in terms of other methods in Logger and should not be called from them. */
   final def log(event: LogEvent): Unit = {
     event match {
-      case s: Success       => success(s.msg)
-      case l: Log           => log(l.level, l.msg)
-      case t: Trace         => trace(t.exception)
+      case s: Success       => if (successEnabled) success(s.msg)
+      case l: Log           => if (atLevel(l.level)) log(l.level, l.msg)
+      case t: Trace         => if (traceEnabled) trace(t.exception)
       case setL: SetLevel   => setLevel(setL.newLevel)
       case setT: SetTrace   => setTrace(setT.level)
       case setS: SetSuccess => setSuccessEnabled(setS.enabled)