Merge pull request #4664 from eatkins/m3-io-fixes

M3 io fixes

.appveyor.yml

@@ -23,7 +23,7 @@ install:
   - SET PATH=C:\sbt\sbt\bin;%PATH%
   - SET SBT_OPTS=-XX:MaxPermSize=2g -Xmx4g -Dsbt.supershell=never -Dfile.encoding=UTF8
 test_script:
-  - sbt "scripted actions/*" "testOnly sbt.ServerSpec"
+  - sbt "scripted actions/* classloader-cache/* nio/* watch/*" "testOnly sbt.ServerSpec"
 
 cache:
   - '%USERPROFILE%\.ivy2\cache'

main-command/src/main/scala/sbt/MainControl.scala

@@ -20,6 +20,9 @@ final case class Reboot(
 ) extends xsbti.Reboot {
   def arguments = argsList.toArray
 }
+
+case object Reload extends Exception
+
 final case class ApplicationID(
     groupID: String,
     name: String,

main/src/main/scala/sbt/Defaults.scala

@@ -37,6 +37,7 @@ import sbt.internal.librarymanagement.mavenint.{
   SbtPomExtraProperties
 }
 import sbt.internal.librarymanagement.{ CustomHttp => _, _ }
+import sbt.internal.nio.{ CheckBuildSources, Globs }
 import sbt.internal.server.{
   Definition,
   LanguageServerProtocol,
@@ -67,7 +68,7 @@ import sbt.librarymanagement.ivy._
 import sbt.librarymanagement.syntax._
 import sbt.nio.Watch
 import sbt.nio.Keys._
-import sbt.nio.file.FileTreeView
+import sbt.nio.file.{ FileTreeView, Glob, RecursiveGlob }
 import sbt.nio.file.syntax._
 import sbt.std.TaskExtra._
 import sbt.testing.{ AnnotatedFingerprint, Framework, Runner, SubclassFingerprint }
@@ -151,13 +152,15 @@ object Defaults extends BuildCommon {
       fileInputs :== Nil,
       inputFileStamper :== sbt.nio.FileStamper.Hash,
       outputFileStamper :== sbt.nio.FileStamper.LastModified,
-      watchForceTriggerOnAnyChange :== true,
+      onChangedBuildSource :== sbt.nio.Keys.WarnOnSourceChanges,
+      watchForceTriggerOnAnyChange :== false,
+      watchPersistFileStamps :== true,
       watchTriggers :== Nil,
       clean := { () },
-      sbt.nio.Keys.fileAttributeMap := {
+      sbt.nio.Keys.fileStampCache := {
         state.value
-          .get(sbt.nio.Keys.persistentFileAttributeMap)
+          .get(sbt.nio.Keys.persistentFileStampCache)
-          .getOrElse(new sbt.nio.Keys.FileAttributeMap)
+          .getOrElse(new sbt.nio.FileStamp.Cache)
       },
     ) ++ TaskRepository
       .proxy(GlobalScope / classLoaderCache, ClassLoaderCache(4)) ++ globalIvyCore ++ globalJvmCore
@@ -253,18 +256,10 @@ object Defaults extends BuildCommon {
       outputStrategy :== None, // TODO - This might belong elsewhere.
       buildStructure := Project.structure(state.value),
       settingsData := buildStructure.value.data,
-      settingsData / fileInputs := {
+      aggregate in checkBuildSources :== false,
-        val baseDir = file(".").getCanonicalFile
+      checkBuildSources / Continuous.dynamicInputs := None,
-        val sourceFilter = ("*.sbt" || "*.scala" || "*.java")
+      checkBuildSources / fileInputs := CheckBuildSources.buildSourceFileInputs.value,
-        val projectDir = baseDir / "project"
+      checkBuildSources := CheckBuildSources.needReloadImpl.value,
-        Seq(
-          baseDir * "*.sbt",
-          projectDir * sourceFilter,
-          // We only want to recursively look in source because otherwise we have to search
-          // the project target directories which is expensive.
-          projectDir / "src" ** sourceFilter,
-        )
-      },
       trapExit :== true,
       connectInput :== false,
       cancelable :== true,
@@ -360,7 +355,6 @@ object Defaults extends BuildCommon {
       watchStartMessage :== Watch.defaultStartWatch,
       watchTasks := Continuous.continuousTask.evaluated,
       aggregate in watchTasks :== false,
-      watchTrackMetaBuild :== true,
       watchTriggeredMessage :== Watch.defaultOnTriggerMessage,
     )
   )
@@ -419,8 +413,11 @@ object Defaults extends BuildCommon {
         case NothingFilter | HiddenFileFilter => include
         case exclude                          => include -- exclude
       }
-      val baseSources = if (sourcesInBase.value) baseDirectory.value * filter :: Nil else Nil
+      val baseSources =
-      unmanagedSourceDirectories.value.map(_ ** filter) ++ baseSources
+        if (sourcesInBase.value) Globs(baseDirectory.value.toPath, recursive = false, filter) :: Nil
+        else Nil
+      unmanagedSourceDirectories.value
+        .map(d => Globs(d.toPath, recursive = true, filter)) ++ baseSources
     },
     unmanagedSources := (unmanagedSources / inputFileStamps).value.map(_._1.toFile),
     managedSourceDirectories := Seq(sourceManaged.value),
@@ -451,9 +448,9 @@ object Defaults extends BuildCommon {
         case NothingFilter | HiddenFileFilter => include
         case exclude                          => include -- exclude
       }
-      unmanagedResourceDirectories.value.map(_ ** filter)
+      unmanagedResourceDirectories.value.map(d => Globs(d.toPath, recursive = true, filter))
     },
-    unmanagedResources := (unmanagedResources / allInputFiles).value.map(_.toFile),
+    unmanagedResources := (unmanagedResources / inputFileStamps).value.map(_._1.toFile),
     resourceGenerators :== Nil,
     resourceGenerators += Def.task {
       PluginDiscovery.writeDescriptors(discoveredSbtPlugins.value, resourceManaged.value)
@@ -596,7 +593,7 @@ object Defaults extends BuildCommon {
     compileInputsSettings
   ) ++ configGlobal ++ defaultCompileSettings ++ compileAnalysisSettings ++ Seq(
     clean := Clean.task(ThisScope, full = false).value,
-    fileOutputs := Seq(classDirectory.value ** "*.class"),
+    fileOutputs := Seq(Glob(classDirectory.value, RecursiveGlob / "*.class")),
     compile := compileTask.value,
     internalDependencyConfigurations := InternalDependencies.configurations.value,
     manipulateBytecode := compileIncremental.value,
@@ -651,10 +648,8 @@ object Defaults extends BuildCommon {
     cleanKeepGlobs := historyPath.value.map(_.toGlob).toSeq,
     clean := Def.taskDyn(Clean.task(resolvedScoped.value.scope, full = true)).value,
     consoleProject := consoleProjectTask.value,
-    watchTransitiveSources := watchTransitiveSourcesTask.value,
-    watch := watchSetting.value,
     transitiveDynamicInputs := SettingsGraph.task.value,
-  )
+  ) ++ sbt.internal.DeprecatedContinuous.taskDefinitions
 
   def generate(generators: SettingKey[Seq[Task[Seq[File]]]]): Initialize[Task[Seq[File]]] =
     generators { _.join.map(_.flatten) }
@@ -1251,7 +1246,7 @@ object Defaults extends BuildCommon {
   ): Initialize[Task[Seq[File]]] = Def.task {
     val filter = include.toTask.value -- exclude.toTask.value
     val view = fileTreeView.value
-    view.list(dirs.toTask.value.map(_ ** filter)).collect {
+    view.list(dirs.toTask.value.map(f => Globs(f.toPath, recursive = true, filter))).collect {
       case (p, a) if !a.isDirectory => p.toFile
     }
   }
@@ -1619,7 +1614,7 @@ object Defaults extends BuildCommon {
       val contents = AnalysisContents.create(analysisResult.analysis(), analysisResult.setup())
       store.set(contents)
     }
-    val map = sbt.nio.Keys.fileAttributeMap.value
+    val map = sbt.nio.Keys.fileStampCache.value
     val analysis = analysisResult.analysis
     import scala.collection.JavaConverters._
     analysis.readStamps.getAllProductStamps.asScala.foreach {
@@ -2574,16 +2569,16 @@ object Classpaths {
             }
           },
           ivyConfiguration := InlineIvyConfiguration(
-            paths = ivyPaths.value,
+            lock = Option(lock(appConfiguration.value)),
+            log = Option(streams.value.log),
+            updateOptions = UpdateOptions(),
+            paths = Option(ivyPaths.value),
             resolvers = externalResolvers.value.toVector,
             otherResolvers = Vector.empty,
             moduleConfigurations = Vector.empty,
-            lock = Option(lock(appConfiguration.value)),
             checksums = checksums.value.toVector,
             managedChecksums = false,
             resolutionCacheDir = Some(crossTarget.value / "resolution-cache"),
-            updateOptions = UpdateOptions(),
-            log = streams.value.log
           ),
           ivySbt := ivySbt0.value,
           classifiersModule := classifiersModuleTask.value,
@@ -3065,7 +3060,8 @@ object Classpaths {
     Def.taskDyn {
       val dirs = productDirectories.value
       val view = fileTreeView.value
-      def containsClassFile(): Boolean = view.list(dirs.map(_ ** "*.class")).nonEmpty
+      def containsClassFile(): Boolean =
+        view.list(dirs.map(Glob(_, RecursiveGlob / "*.class"))).nonEmpty
       TrackLevel.intersection(track, exportToInternal.value) match {
         case TrackLevel.TrackAlways =>
           Def.task {

main/src/main/scala/sbt/EvaluateTask.scala

@@ -16,9 +16,10 @@ import sbt.Project.richInitializeTask
 import sbt.Scope.Global
 import sbt.internal.Aggregation.KeyValue
 import sbt.internal.TaskName._
-import sbt.internal.util._
 import sbt.internal._
+import sbt.internal.util._
 import sbt.librarymanagement.{ Resolver, UpdateReport }
+import sbt.nio.Keys.IgnoreSourceChanges
 import sbt.std.Transform.DummyTaskMap
 import sbt.util.{ Logger, Show }
 
@@ -274,7 +275,7 @@ object EvaluateTask {
   def injectSettings: Seq[Setting[_]] = Seq(
     (state in Global) ::= dummyState,
     (streamsManager in Global) ::= Def.dummyStreamsManager,
-    (executionRoots in Global) ::= dummyRoots
+    (executionRoots in Global) ::= dummyRoots,
   )
 
   @deprecated("Use variant which doesn't take a logger", "1.1.1")
@@ -346,7 +347,7 @@ object EvaluateTask {
       ExceptionCategory(ex) match {
         case AlreadyHandled => ()
         case m: MessageOnly => if (msg.isEmpty) log.error(m.message)
-        case f: Full        => log.trace(f.exception)
+        case f: Full        => if (f.exception != Reload) log.trace(f.exception)
       }
     }
 
@@ -439,7 +440,7 @@ object EvaluateTask {
       case Some(t: Task[_]) => transformNode(t).isEmpty
       case _                => true
     }
-    def run() = {
+    def run[R](s: State, toRun: Task[R], doShutdown: Boolean) = {
       val x = new Execute[Task](
         Execute.config(config.checkCycles, overwriteNode),
         triggers,
@@ -447,12 +448,12 @@ object EvaluateTask {
       )(taskToNode)
       val (newState, result) =
         try {
-          val results = x.runKeep(root)(service)
+          val results = x.runKeep(toRun)(service)
-          storeValuesForPrevious(results, state, streams)
+          storeValuesForPrevious(results, s, streams)
-          applyResults(results, state, root)
+          applyResults(results, s, toRun)
-        } catch { case inc: Incomplete => (state, Inc(inc)) } finally shutdown()
+        } catch { case inc: Incomplete => (s, Inc(inc)) } finally if (doShutdown) shutdown()
       val replaced = transformInc(result)
-      logIncResult(replaced, state, streams)
+      logIncResult(replaced, s, streams)
       (newState, replaced)
     }
     object runningEngine extends RunningTaskEngine {
@@ -466,8 +467,24 @@ object EvaluateTask {
     // Register with our cancel handler we're about to start.
     val strat = config.cancelStrategy
     val cancelState = strat.onTaskEngineStart(runningEngine)
-    try run()
+    try {
-    finally {
+      (state.get(stateBuildStructure), state.get(sessionSettings)) match {
+        case (Some(structure), Some(settings)) =>
+          val extracted: Extracted = Project.extract(settings, structure)
+          if (extracted.get(sbt.nio.Keys.onChangedBuildSource) == IgnoreSourceChanges) {
+            run(state, root, doShutdown = true)
+          } else {
+            run(state, extracted.get(sbt.nio.Keys.checkBuildSources), doShutdown = false) match {
+              case (newState, r) =>
+                r.toEither match {
+                  case Left(i) => (newState, Result.fromEither(Left(i)))
+                  case _       => run(newState, root, doShutdown = true)
+                }
+            }
+          }
+        case _ => run(state, root, doShutdown = true)
+      }
+    } finally {
       strat.onTaskEngineFinish(cancelState)
       currentlyRunningEngine.set(null)
       lastEvaluatedState.set(SafeState(state))

main/src/main/scala/sbt/Main.scala

@@ -69,6 +69,7 @@ final class xMain extends xsbti.AppMain {
       override def scalaProvider(): ScalaProvider = appProvider.scalaProvider
       override def id(): xsbti.ApplicationID = appProvider.id()
       override def loader(): ClassLoader = metaLoader
+      @deprecated("Implements deprecated api", "1.3.0")
       override def mainClass(): Class[_ <: AppMain] = appProvider.mainClass()
       override def entryPoint(): Class[_] = appProvider.entryPoint()
       override def newMain(): AppMain = appProvider.newMain()
@@ -266,7 +267,7 @@ object BuiltinCommands {
       BasicCommands.multi,
       act,
       continuous,
-      clearCaches
+      clearCaches,
     ) ++ allBasicCommands
 
   def DefaultBootCommands: Seq[String] =
@@ -879,6 +880,7 @@ object BuiltinCommands {
     val session = Load.initialSession(structure, eval, s0)
     SessionSettings.checkSession(session, s)
     registerGlobalCaches(Project.setProject(session, structure, s))
+      .put(sbt.nio.Keys.hasCheckedMetaBuild, new AtomicBoolean(false))
   }
 
   def registerCompilerCache(s: State): State = {

main/src/main/scala/sbt/MainLoop.scala

@@ -11,16 +11,15 @@ import java.io.PrintWriter
 import java.util.Properties
 
 import jline.TerminalFactory
+import sbt.internal.langserver.ErrorCodes
+import sbt.internal.util.{ ErrorHandling, GlobalLogBacking }
+import sbt.io.{ IO, Using }
+import sbt.protocol._
+import sbt.util.Logger
 
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
 
-import sbt.io.{ IO, Using }
-import sbt.internal.util.{ ErrorHandling, GlobalLogBacking }
-import sbt.internal.langserver.ErrorCodes
-import sbt.util.Logger
-import sbt.protocol._
-
 object MainLoop {
 
   /** Entry point to run the remaining commands in State with managed global logging.*/
@@ -140,7 +139,10 @@ object MainLoop {
       case Right(s)                  => s
       case Left(t: xsbti.FullReload) => throw t
       case Left(t: RebootCurrent)    => throw t
-      case Left(t)                   => state.handleError(t)
+      case Left(Reload) =>
+        val remaining = state.currentCommand.toList ::: state.remainingCommands
+        state.copy(remainingCommands = Exec("reload", None, None) :: remaining)
+      case Left(t) => state.handleError(t)
     }
 
   /** This is the main function State transfer function of the sbt command processing. */

main/src/main/scala/sbt/Project.scala

@@ -29,7 +29,6 @@ import Keys.{
   serverConnectionType,
   fullServerHandlers,
   logLevel,
-  watch
 }
 import Scope.{ Global, ThisScope }
 import Def.{ Flattened, Initialize, ScopedKey, Setting }
@@ -509,7 +508,6 @@ object Project extends ProjectExtra {
     val history = get(historyPath) flatMap idFun
     val prompt = get(shellPrompt)
     val trs = (templateResolverInfos in Global get structure.data).toList.flatten
-    val watched = get(watch)
     val startSvr: Option[Boolean] = get(autoStartServer)
     val host: Option[String] = get(serverHost)
     val port: Option[Int] = get(serverPort)
@@ -524,7 +522,6 @@ object Project extends ProjectExtra {
     )
     val newAttrs =
       s.attributes
-        .setCond(Watched.Configuration, watched)
         .put(historyPath.key, history)
         .setCond(autoStartServer.key, startSvr)
         .setCond(serverPort.key, port)

main/src/main/scala/sbt/ScriptedPlugin.scala

@@ -10,20 +10,17 @@ package sbt
 import java.io.File
 import java.lang.reflect.Method
 
+import sbt.Def._
+import sbt.Keys._
+import sbt.Project._
+import sbt.internal.inc.ModuleUtilities
+import sbt.internal.inc.classpath.ClasspathUtilities
+import sbt.internal.util.complete.{ DefaultParsers, Parser }
 import sbt.io._
 import sbt.io.syntax._
-
-import sbt.internal.util.complete.{ Parser, DefaultParsers }
-
 import sbt.librarymanagement._
 import sbt.librarymanagement.syntax._
-
+import sbt.nio.file.{ Glob, RecursiveGlob }
-import sbt.internal.inc.classpath.ClasspathUtilities
-import sbt.internal.inc.ModuleUtilities
-
-import Def._
-import Keys._
-import Project._
 
 object ScriptedPlugin extends AutoPlugin {
 
@@ -89,7 +86,7 @@ object ScriptedPlugin extends AutoPlugin {
       use(analysis, pub)
     },
     scripted := scriptedTask.evaluated,
-    watchTriggers in scripted += sbtTestDirectory.value ** AllPassFilter
+    watchTriggers in scripted += Glob(sbtTestDirectory.value, RecursiveGlob)
   )
 
   private[sbt] def scriptedTestsTask: Initialize[Task[AnyRef]] =

main/src/main/scala/sbt/internal/Aggregation.scala

@@ -111,6 +111,9 @@ object Aggregation {
     val complete = timedRun[T](s, ts, extra)
     showRun(complete, show)
     complete.results match {
+      case Inc(i) if i.directCause.contains(Reload) =>
+        val remaining = s.currentCommand.toList ::: s.remainingCommands
+        complete.state.copy(remainingCommands = Exec("reload", None, None) :: remaining)
       case Inc(i)   => complete.state.handleError(i)
       case Value(_) => complete.state
     }

main/src/main/scala/sbt/internal/Clean.scala

@@ -14,7 +14,6 @@ import java.nio.file.{ DirectoryNotEmptyException, Files, Path }
 import sbt.Def._
 import sbt.Keys._
 import sbt.Project.richInitializeTask
-import sbt.io.AllPassFilter
 import sbt.io.syntax._
 import sbt.nio.Keys._
 import sbt.nio.file._
@@ -54,7 +53,7 @@ private[sbt] object Clean {
   private[this] def cleanFilter(scope: Scope): Def.Initialize[Task[Path => Boolean]] = Def.task {
     val excludes = (cleanKeepFiles in scope).value.map {
       // This mimics the legacy behavior of cleanFilesTask
-      case f if f.isDirectory => f * AllPassFilter
+      case f if f.isDirectory => Glob(f, AnyPath)
       case f                  => f.toGlob
     } ++ (cleanKeepGlobs in scope).value
     p: Path => excludes.exists(_.matches(p))

main/src/main/scala/sbt/internal/Continuous.scala

@@ -9,7 +9,7 @@ package sbt
 package internal
 
 import java.io.{ ByteArrayInputStream, InputStream, File => _ }
-import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.atomic.{ AtomicBoolean, AtomicInteger }
 
 import sbt.BasicCommandStrings.{
   ContinuousExecutePrefix,
@@ -125,8 +125,10 @@ private[sbt] object Continuous extends DeprecatedContinuous {
   private[sbt] val dynamicInputs = taskKey[Option[mutable.Set[DynamicInput]]](
     "The input globs found during task evaluation that are used in watch."
   )
+
   private[sbt] def dynamicInputsImpl: Def.Initialize[Task[Option[mutable.Set[DynamicInput]]]] =
     Def.task(Keys.state.value.get(DynamicInputs))
+
   private[sbt] val DynamicInputs =
     AttributeKey[mutable.Set[DynamicInput]](
       "dynamic-inputs",
@@ -136,6 +138,7 @@ private[sbt] object Continuous extends DeprecatedContinuous {
 
   private[this] val continuousParser: State => Parser[(Int, String)] = {
     def toInt(s: String): Int = Try(s.toInt).getOrElse(0)
+
     // This allows us to re-enter the watch with the previous count.
     val digitParser: Parser[Int] =
       (Parsers.Space.* ~> matched(Parsers.Digit.+) <~ Parsers.Space.*).map(toInt)
@@ -189,6 +192,7 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       watchSettings
     )
   }
+
   private def getRepository(state: State): FileTreeRepository[FileAttributes] = {
     lazy val exception =
       new IllegalStateException("Tried to access FileTreeRepository for uninitialized state")
@@ -265,13 +269,45 @@ private[sbt] object Continuous extends DeprecatedContinuous {
     f(commands, s, valid, invalid)
   }
 
-  private[this] def withCharBufferedStdIn[R](f: InputStream => R): R =
+  private[this] def withCharBufferedStdIn[R](f: InputStream => R): R = {
-    if (!Util.isWindows) {
+    val terminal = JLine.terminal
-      val terminal = JLine.terminal
+    terminal.init()
-      terminal.init()
+    terminal.setEchoEnabled(true)
-      terminal.setEchoEnabled(true)
+    val wrapped = terminal.wrapInIfNeeded(System.in)
-      f(terminal.wrapInIfNeeded(System.in))
+    if (Util.isNonCygwinWindows) {
-    } else f(System.in)
+      val inputStream: InputStream with AutoCloseable = new InputStream with AutoCloseable {
+        private[this] val buffer = new java.util.LinkedList[Int]
+        private[this] val closed = new AtomicBoolean(false)
+        private[this] val thread = new Thread("Continuous-input-stream-reader") {
+          setDaemon(true)
+          start()
+          @tailrec
+          override def run(): Unit = {
+            try {
+              if (!closed.get()) {
+                buffer.add(wrapped.read())
+              }
+            } catch {
+              case _: InterruptedException =>
+            }
+            if (!closed.get()) run()
+          }
+        }
+        override def available(): Int = buffer.size()
+        override def read(): Int = buffer.poll()
+        override def close(): Unit = if (closed.compareAndSet(false, true)) {
+          thread.interrupt()
+        }
+      }
+      try {
+        f(inputStream)
+      } finally {
+        inputStream.close()
+      }
+    } else {
+      f(wrapped)
+    }
+  }
 
   private[sbt] def runToTermination(
       state: State,
@@ -287,17 +323,22 @@ private[sbt] object Continuous extends DeprecatedContinuous {
     } else {
       FileTreeRepository.default
     }
+    val fileStampCache = new FileStamp.Cache
+    repo.addObserver(t => fileStampCache.invalidate(t.path))
     try {
-      val stateWithRepo = state
+      val stateWithRepo = state.put(globalFileTreeRepository, repo)
-        .put(globalFileTreeRepository, repo)
+      val fullState =
-        .put(persistentFileAttributeMap, new sbt.nio.Keys.FileAttributeMap)
+        if (extracted.get(watchPersistFileStamps))
-      setup(stateWithRepo, command) { (commands, s, valid, invalid) =>
+          stateWithRepo.put(persistentFileStampCache, fileStampCache)
+        else stateWithRepo
+      setup(fullState, command) { (commands, s, valid, invalid) =>
         EvaluateTask.withStreams(extracted.structure, s)(_.use(streams in Global) { streams =>
           implicit val logger: Logger = streams.log
           if (invalid.isEmpty) {
             val currentCount = new AtomicInteger(count)
             val configs = getAllConfigs(valid.map(v => v._1 -> v._2))
-            val callbacks = aggregate(configs, logger, in, s, currentCount, isCommand, commands)
+            val callbacks =
+              aggregate(configs, logger, in, s, currentCount, isCommand, commands, fileStampCache)
             val task = () => {
               currentCount.getAndIncrement()
               // abort as soon as one of the tasks fails
@@ -307,10 +348,16 @@ private[sbt] object Continuous extends DeprecatedContinuous {
             callbacks.onEnter()
             // Here we enter the Watched.watch state machine. We will not return until one of the
             // state machine callbacks returns Watched.CancelWatch, Watched.Custom, Watched.HandleError
-            // or Watched.Reload. The task defined above will be run at least once. It will be run
+            // or Watched.ReloadException. The task defined above will be run at least once. It will be run
             // additional times whenever the state transition callbacks return Watched.Trigger.
             try {
               val terminationAction = Watch(task, callbacks.onStart, callbacks.nextEvent)
+              terminationAction match {
+                case e: Watch.HandleUnexpectedError =>
+                  System.err.println("Caught unexpected error running continuous build:")
+                  e.throwable.printStackTrace(System.err)
+                case _ =>
+              }
               callbacks.onTermination(terminationAction, command, currentCount.get(), state)
             } finally {
               callbacks.onExit()
@@ -340,6 +387,7 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       case _ => Nil: Seq[ScopedKey[_]]
     }
   }
+
   private def getAllConfigs(
       inputs: Seq[(String, State)]
   )(implicit extracted: Extracted, logger: Logger): Seq[Config] = {
@@ -386,7 +434,8 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       state: State,
       count: AtomicInteger,
       isCommand: Boolean,
-      commands: Seq[String]
+      commands: Seq[String],
+      fileStampCache: FileStamp.Cache
   )(
       implicit extracted: Extracted
   ): Callbacks = {
@@ -396,7 +445,7 @@ private[sbt] object Continuous extends DeprecatedContinuous {
     val onStart: () => Watch.Action = getOnStart(project, commands, configs, rawLogger, count)
     val nextInputEvent: () => Watch.Action = parseInputEvents(configs, state, inputStream, logger)
     val (nextFileEvent, cleanupFileMonitor): (() => Option[(Watch.Event, Watch.Action)], () => Unit) =
-      getFileEvents(configs, rawLogger, state, count, commands)
+      getFileEvents(configs, rawLogger, state, count, commands, fileStampCache)
     val nextEvent: () => Watch.Action =
       combineInputAndFileEvents(nextInputEvent, nextFileEvent, logger)
     val onExit = () => {
@@ -454,41 +503,56 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       res
     }
   }
+
   private def getFileEvents(
       configs: Seq[Config],
       logger: Logger,
       state: State,
       count: AtomicInteger,
-      commands: Seq[String]
+      commands: Seq[String],
+      fileStampCache: FileStamp.Cache
   )(implicit extracted: Extracted): (() => Option[(Watch.Event, Watch.Action)], () => Unit) = {
-    val attributeMap = state.get(persistentFileAttributeMap).get
     val trackMetaBuild = configs.forall(_.watchSettings.trackMetaBuild)
     val buildGlobs =
-      if (trackMetaBuild) extracted.getOpt(fileInputs in settingsData).getOrElse(Nil)
+      if (trackMetaBuild) extracted.getOpt(fileInputs in checkBuildSources).getOrElse(Nil)
       else Nil
 
     val retentionPeriod = configs.map(_.watchSettings.antiEntropyRetentionPeriod).max
     val quarantinePeriod = configs.map(_.watchSettings.deletionQuarantinePeriod).max
     val onEvent: Event => Seq[(Watch.Event, Watch.Action)] = event => {
       val path = event.path
+
       def watchEvent(stamper: FileStamper, forceTrigger: Boolean): Option[Watch.Event] = {
-        val stamp = FileStamp(path, stamper)
         if (!event.exists) {
-          attributeMap.remove(event.path) match {
+          Some(Deletion(event))
+          fileStampCache.remove(event.path) match {
             case null => None
             case _    => Some(Deletion(event))
           }
         } else {
-          import sbt.internal.inc.Stamp.equivStamp
+          fileStampCache.update(path, stamper) match {
-          attributeMap.put(path, stamp) match {
+            case (None, Some(_)) => Some(Creation(event))
-            case null => Some(Creation(event))
+            case (Some(_), None) => Some(Deletion(event))
-            case s =>
+            case (Some(p), Some(c)) =>
-              if (forceTrigger || !equivStamp.equiv(s.stamp, stamp.stamp))
+              if (forceTrigger) {
+                val msg =
+                  s"Creating forced update event for path $path (previous stamp: $p, current stamp: $c)"
+                logger.debug(msg)
                 Some(Update(event))
-              else None
+              } else if (p == c) {
+                logger.debug(s"Dropping event for unmodified path $path")
+                None
+              } else {
+                val msg =
+                  s"Creating update event for modified $path (previous stamp: $p, current stamp: $c)"
+                logger.debug(msg)
+                Some(Update(event))
+              }
+            case _ => None
           }
         }
       }
+
       if (buildGlobs.exists(_.matches(path))) {
         watchEvent(FileStamper.Hash, forceTrigger = false).map(e => e -> Watch.Reload).toSeq
       } else {
@@ -519,13 +583,27 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       private implicit class WatchLogger(val l: Logger) extends sbt.internal.nio.WatchLogger {
         override def debug(msg: Any): Unit = l.debug(msg.toString)
       }
+
       // TODO make this a normal monitor
       private[this] val monitors: Seq[FileEventMonitor[Event]] =
         configs.map { config =>
           // Create a logger with a scoped key prefix so that we can tell from which
           // monitor events occurred.
           FileEventMonitor.antiEntropy(
-            getRepository(state),
+            new Observable[Event] {
+              private[this] val repo = getRepository(state)
+              private[this] val observers = new Observers[Event] {
+                override def onNext(t: Event): Unit =
+                  if (config.inputs().exists(_.glob.matches(t.path))) super.onNext(t)
+              }
+              private[this] val handle = repo.addObserver(observers)
+              override def addObserver(observer: Observer[Event]): AutoCloseable =
+                observers.addObserver(observer)
+              override def close(): Unit = {
+                handle.close()
+                observers.close()
+              }
+            },
             config.watchSettings.antiEntropy,
             logger.withPrefix(config.key.show),
             config.watchSettings.deletionQuarantinePeriod,
@@ -543,11 +621,13 @@ private[sbt] object Continuous extends DeprecatedContinuous {
                   retentionPeriod
                 ) :: Nil
               } else Nil)
+
       override def poll(duration: Duration, filter: Event => Boolean): Seq[Event] = {
         val res = monitors.flatMap(_.poll(0.millis, filter)).toSet.toVector
         if (res.isEmpty) Thread.sleep(duration.toMillis)
         res
       }
+
       override def close(): Unit = monitors.foreach(_.close())
     }
     val watchLogger: WatchLogger = msg => logger.debug(msg.toString)
@@ -640,7 +720,9 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       val parser = any ~> inputParser ~ matched(any)
       // Each parser gets its own copy of System.in that it can modify while parsing.
       val systemInBuilder = new StringBuilder
+
       def inputStream(string: String): InputStream = new ByteArrayInputStream(string.getBytes)
+
       // This string is provided in the closure below by reading from System.in
       val default: String => Watch.Action =
         string => parse(inputStream(string), systemInBuilder, parser)
@@ -726,7 +808,9 @@ private[sbt] object Continuous extends DeprecatedContinuous {
      */
     new Logger {
       override def trace(t: => Throwable): Unit = logger.trace(t)
+
       override def success(message: => String): Unit = logger.success(message)
+
       override def log(level: Level.Value, message: => String): Unit = {
         val levelString = if (level < delegateLevel) s"[$level] " else ""
         val newMessage = s"[watch] $levelString$message"
@@ -786,7 +870,8 @@ private[sbt] object Continuous extends DeprecatedContinuous {
     val onTermination: Option[(Watch.Action, String, Int, State) => State] =
       key.get(watchOnTermination)
     val startMessage: StartMessage = getStartMessage(key)
-    val trackMetaBuild: Boolean = key.get(watchTrackMetaBuild).getOrElse(true)
+    val trackMetaBuild: Boolean =
+      key.get(onChangedBuildSource).fold(false)(_ == ReloadOnSourceChanges)
     val triggerMessage: TriggerMessage = getTriggerMessage(key)
 
     // Unlike the rest of the settings, InputStream is a TaskKey which means that if it is set,
@@ -812,12 +897,15 @@ private[sbt] object Continuous extends DeprecatedContinuous {
   ) {
     private[sbt] def watchState(count: Int): DeprecatedWatchState =
       WatchState.empty(inputs().map(_.glob)).withCount(count)
+
     def arguments(logger: Logger): Arguments = new Arguments(logger, inputs())
   }
+
   private def getStartMessage(key: ScopedKey[_])(implicit e: Extracted): StartMessage = Some {
     lazy val default = key.get(watchStartMessage).getOrElse(Watch.defaultStartWatch)
     key.get(deprecatedWatchingMessage).map(Left(_)).getOrElse(Right(default))
   }
+
   private def getTriggerMessage(
       key: ScopedKey[_]
   )(implicit e: Extracted): TriggerMessage = {
@@ -926,9 +1014,12 @@ private[sbt] object Continuous extends DeprecatedContinuous {
      */
     def withPrefix(prefix: String): Logger = new Logger {
       override def trace(t: => Throwable): Unit = logger.trace(t)
+
       override def success(message: => String): Unit = logger.success(message)
+
       override def log(level: Level.Value, message: => String): Unit =
         logger.log(level, s"$prefix - $message")
     }
   }
+
 }

main/src/main/scala/sbt/internal/DeprecatedContinuous.scala

@@ -19,3 +19,9 @@ private[internal] trait DeprecatedContinuous {
   protected val deprecatedWatchingMessage = sbt.Keys.watchingMessage
   protected val deprecatedTriggeredMessage = sbt.Keys.triggeredMessage
 }
+private[sbt] object DeprecatedContinuous {
+  private[sbt] val taskDefinitions = Seq(
+    sbt.Keys.watchTransitiveSources := sbt.Defaults.watchTransitiveSourcesTask.value,
+    sbt.Keys.watch := sbt.Defaults.watchSetting.value,
+  )
+}

main/src/main/scala/sbt/internal/ExternalHooks.scala

@@ -12,11 +12,13 @@ import java.util.Optional
 
 import sbt.Def
 import sbt.Keys._
-import sbt.internal.inc.{ EmptyStamp, ExternalLookup, Stamper }
+import sbt.internal.inc.ExternalLookup
+import sbt.internal.inc.Stamp.equivStamp.equiv
 import sbt.io.syntax._
 import sbt.nio.Keys._
 import sbt.nio.file.RecursiveGlob
 import sbt.nio.file.syntax._
+import sbt.nio.{ FileStamp, FileStamper }
 import xsbti.compile._
 import xsbti.compile.analysis.Stamp
 
@@ -25,37 +27,22 @@ import scala.collection.mutable
 
 private[sbt] object ExternalHooks {
   private val javaHome = Option(System.getProperty("java.home")).map(Paths.get(_))
-  private[this] implicit class StampOps(val s: Stamp) extends AnyVal {
-    def hash: String = s.getHash.orElse("")
-    def lastModified: Long = s.getLastModified.orElse(-1L)
-  }
   def default: Def.Initialize[sbt.Task[ExternalHooks]] = Def.task {
-    val attributeMap = fileAttributeMap.value
+    val cache = fileStampCache.value
     val cp = dependencyClasspath.value.map(_.data)
     cp.foreach { file =>
       val path = file.toPath
-      attributeMap.get(path) match {
+      cache.getOrElseUpdate(path, FileStamper.LastModified)
-        case null => attributeMap.put(path, sbt.nio.FileStamp.lastModified(path))
-        case _    =>
-      }
     }
     val classGlob = classDirectory.value.toGlob / RecursiveGlob / "*.class"
     fileTreeView.value.list(classGlob).foreach {
-      case (path, _) => attributeMap.put(path, sbt.nio.FileStamp.lastModified(path))
+      case (path, _) => cache.update(path, FileStamper.LastModified)
     }
-    apply(
+    apply((compileOptions in compile).value, cache)
-      (compileOptions in compile).value,
-      (file: File) => {
-        attributeMap.get(file.toPath) match {
-          case null => EmptyStamp
-          case s    => s.stamp
-        }
-      }
-    )
   }
   private def apply(
       options: CompileOptions,
-      attributeMap: File => Stamp
+      fileStampCache: FileStamp.Cache
   ): DefaultExternalHooks = {
     val lookup = new ExternalLookup {
       override def changedSources(previousAnalysis: CompileAnalysis): Option[Changes[File]] = Some {
@@ -70,16 +57,10 @@ private[sbt] object ExternalHooks {
             previousAnalysis.readStamps().getAllSourceStamps.asScala
           prevSources.foreach {
             case (file: File, s: Stamp) =>
-              attributeMap(file) match {
+              fileStampCache.getOrElseUpdate(file.toPath, FileStamper.Hash) match {
-                case null =>
+                case None => getRemoved.add(file)
-                  getRemoved.add(file)
+                case Some(stamp) =>
-                case stamp =>
+                  if (equiv(stamp.stamp, s)) getUnmodified.add(file) else getChanged.add(file)
-                  val hash = (if (stamp.getHash.isPresent) stamp else Stamper.forHash(file)).hash
-                  if (hash == s.hash) {
-                    getUnmodified.add(file)
-                  } else {
-                    getChanged.add(file)
-                  }
               }
           }
           options.sources.foreach(file => if (!prevSources.contains(file)) getAdded.add(file))
@@ -98,8 +79,8 @@ private[sbt] object ExternalHooks {
       override def changedBinaries(previousAnalysis: CompileAnalysis): Option[Set[File]] = {
         Some(previousAnalysis.readStamps.getAllBinaryStamps.asScala.flatMap {
           case (file, stamp) =>
-            attributeMap(file) match {
+            fileStampCache.get(file.toPath) match {
-              case cachedStamp if stamp.getLastModified == cachedStamp.getLastModified => None
+              case Some(cachedStamp) if equiv(cachedStamp.stamp, stamp) => None
               case _ =>
                 javaHome match {
                   case Some(h) if file.toPath.startsWith(h) => None
@@ -112,9 +93,9 @@ private[sbt] object ExternalHooks {
       override def removedProducts(previousAnalysis: CompileAnalysis): Option[Set[File]] = {
         Some(previousAnalysis.readStamps.getAllProductStamps.asScala.flatMap {
           case (file, stamp) =>
-            attributeMap(file) match {
+            fileStampCache.get(file.toPath) match {
-              case s if s.getLastModified == stamp.getLastModified => None
+              case Some(s) if equiv(s.stamp, stamp) => None
-              case _                                               => Some(file)
+              case _                                => Some(file)
             }
         }.toSet)
       }

main/src/main/scala/sbt/internal/IvyConsole.scala

@@ -57,7 +57,7 @@ object IvyConsole {
         depSettings
       )
 
-      val newStructure = Load.reapply(session.original ++ append, structure, state.log)
+      val newStructure = Load.reapply(session.original ++ append, structure)
       val newState = state.copy(remainingCommands = Exec(Keys.consoleQuick.key.label, None) :: Nil)
       Project.setProject(session, newStructure, newState)
     }

main/src/main/scala/sbt/internal/RelayAppender.scala

@@ -13,13 +13,20 @@ import org.apache.logging.log4j.core.{ LogEvent => XLogEvent }
 import org.apache.logging.log4j.core.appender.AbstractAppender
 import org.apache.logging.log4j.core.layout.PatternLayout
 import org.apache.logging.log4j.core.async.RingBufferLogEvent
+import org.apache.logging.log4j.core.config.Property
 import sbt.util.Level
 import sbt.internal.util._
 import sbt.protocol.LogEvent
 import sbt.internal.util.codec._
 
 class RelayAppender(name: String)
-    extends AbstractAppender(name, null, PatternLayout.createDefaultLayout(), true) {
+    extends AbstractAppender(
+      name,
+      null,
+      PatternLayout.createDefaultLayout(),
+      true,
+      Property.EMPTY_ARRAY
+    ) {
   lazy val exchange = StandardMain.exchange
 
   def append(event: XLogEvent): Unit = {

main/src/main/scala/sbt/internal/SettingsGraph.scala

@@ -12,9 +12,9 @@ import sbt.Keys._
 import sbt.Project.richInitializeTask
 import sbt._
 import sbt.internal.io.Source
+import sbt.internal.nio.Globs
 import sbt.internal.util.AttributeMap
 import sbt.internal.util.complete.Parser
-import sbt.io.syntax._
 import sbt.nio.FileStamper
 import sbt.nio.Keys._
 import sbt.nio.file.Glob
@@ -25,7 +25,7 @@ private[sbt] object SettingsGraph {
   private implicit class SourceOps(val source: Source) {
     def toGlob: Glob = {
       val filter = source.includeFilter -- source.excludeFilter
-      if (source.recursive) source.base ** filter else source.base * filter
+      Globs.apply(source.base.toPath, source.recursive, filter)
     }
   }
   private[sbt] def task: Def.Initialize[Task[Seq[DynamicInput]]] =
@@ -106,7 +106,7 @@ private[sbt] object SettingsGraph {
         .map { am =>
           am.get(scopedKey.key) match {
             case Some(globs: Seq[Glob]) =>
-              if (trigger) {
+              if (!trigger) {
                 val stamper = am.get(inputFileStamper.key).getOrElse(FileStamper.Hash)
                 val forceTrigger = am.get(watchForceTriggerOnAnyChange.key).getOrElse(false)
                 globs.map(g => DynamicInput(g, stamper, forceTrigger))

main/src/main/scala/sbt/internal/nio/CheckBuildSources.scala

@@ -0,0 +1,65 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal.nio
+
+import sbt.Keys.{ baseDirectory, state, streams }
+import sbt.SlashSyntax0._
+import sbt.io.syntax._
+import sbt.nio.Keys._
+import sbt.nio.file.{ ChangedFiles, Glob, RecursiveGlob }
+
+private[sbt] object CheckBuildSources {
+  private[sbt] def needReloadImpl: Def.Initialize[Task[Unit]] = Def.task {
+    val logger = streams.value.log
+    val checkMetaBuildParam = state.value.get(hasCheckedMetaBuild)
+    val firstTime = checkMetaBuildParam.fold(true)(_.get == false)
+    (onChangedBuildSource in Scope.Global).value match {
+      case IgnoreSourceChanges => ()
+      case o =>
+        logger.debug("Checking for meta build source updates")
+        (changedInputFiles in checkBuildSources).value match {
+          case Some(cf: ChangedFiles) if !firstTime =>
+            val rawPrefix = s"Meta build source files have changed:\n" +
+              (if (cf.created.nonEmpty) s"creations: ${cf.created.mkString("\n  ", "  \n", "\n")}"
+               else "") +
+              (if (cf.deleted.nonEmpty) s"deletions: ${cf.deleted.mkString("\n  ", "  \n", "\n")}"
+               else "") +
+              (if (cf.updated.nonEmpty) s"updates: ${cf.updated.mkString("\n  ", "  \n", "\n")}"
+               else "")
+            val prefix = rawPrefix.linesIterator.filterNot(_.trim.isEmpty).mkString("\n")
+            if (o == ReloadOnSourceChanges) {
+              logger.info(s"$prefix\nReloading sbt...")
+              throw Reload
+            } else {
+              val tail = "Reload sbt with the 'reload' command to apply these changes. " +
+                "To automatically reload upon meta build source changed detection, set " +
+                "`Global / onChangedBuildSource := ReloadOnSourceChanges`. To disable this " +
+                "warning, set `Global / onChangedBuildSource := IgnoreSourceChanges`"
+              logger.warn(s"$prefix\n$tail")
+            }
+          case _ => ()
+        }
+    }
+    checkMetaBuildParam.foreach(_.set(true))
+  }
+  private[sbt] def buildSourceFileInputs: Def.Initialize[Seq[Glob]] = Def.setting {
+    if (onChangedBuildSource.value != IgnoreSourceChanges) {
+      val baseDir = (LocalRootProject / baseDirectory).value
+      val sourceFilter = "*.{sbt,scala,java}"
+      val projectDir = baseDir / "project"
+      Seq(
+        Glob(baseDir, "*.sbt"),
+        Glob(projectDir, sourceFilter),
+        // We only want to recursively look in source because otherwise we have to search
+        // the project target directories which is expensive.
+        Glob(projectDir / "src", RecursiveGlob / sourceFilter),
+      )
+    } else Nil
+  }
+}

main/src/main/scala/sbt/nio/FileStamp.scala

@@ -16,8 +16,6 @@ import sbt.nio.file.FileAttributes
 import sjsonnew.{ Builder, JsonFormat, Unbuilder, deserializationError }
 import xsbti.compile.analysis.{ Stamp => XStamp }
 
-import scala.util.Try
-
 sealed trait FileStamper
 object FileStamper {
   case object Hash extends FileStamper
@@ -36,12 +34,11 @@ private[sbt] object FileStamp {
     }
   }
 
-  private[sbt] val converter: (Path, FileAttributes) => Try[FileStamp] = (p, a) => Try(apply(p, a))
+  def apply(path: Path, fileStamper: FileStamper): Option[FileStamp] = fileStamper match {
-  def apply(path: Path, fileStamper: FileStamper): FileStamp = fileStamper match {
     case FileStamper.Hash         => hash(path)
     case FileStamper.LastModified => lastModified(path)
   }
-  def apply(path: Path, fileAttributes: FileAttributes): FileStamp =
+  def apply(path: Path, fileAttributes: FileAttributes): Option[FileStamp] =
     try {
       if (fileAttributes.isDirectory) lastModified(path)
       else
@@ -51,13 +48,21 @@ private[sbt] object FileStamp {
           case _                         => hash(path)
         }
     } catch {
-      case e: IOException => Error(e)
+      case e: IOException => Some(Error(e))
     }
   def hash(string: String): Hash = new FileHashImpl(sbt.internal.inc.Hash.unsafeFromString(string))
-  def hash(path: Path): Hash = new FileHashImpl(Stamper.forHash(path.toFile))
+  def hash(path: Path): Option[Hash] = Stamper.forHash(path.toFile) match {
-  def lastModified(path: Path): LastModified = LastModified(IO.getModifiedTimeOrZero(path.toFile))
+    case EmptyStamp => None
+    case s          => Some(new FileHashImpl(s))
+  }
+  def lastModified(path: Path): Option[LastModified] = IO.getModifiedTimeOrZero(path.toFile) match {
+    case 0 => None
+    case l => Some(LastModified(l))
+  }
   private[this] class FileHashImpl(val xstamp: XStamp) extends Hash(xstamp.getHash.orElse(""))
   sealed abstract case class Hash private[sbt] (hex: String) extends FileStamp
+  final case class LastModified private[sbt] (time: Long) extends FileStamp
+  final case class Error(exception: IOException) extends FileStamp
 
   implicit val pathJsonFormatter: JsonFormat[Seq[Path]] = new JsonFormat[Seq[Path]] {
     override def write[J](obj: Seq[Path], builder: Builder[J]): Unit = {
@@ -207,6 +212,65 @@ private[sbt] object FileStamp {
         }
     }
 
-  final case class LastModified private[sbt] (time: Long) extends FileStamp
+  private implicit class EitherOps(val e: Either[FileStamp, FileStamp]) extends AnyVal {
-  final case class Error(exception: IOException) extends FileStamp
+    def value: Option[FileStamp] = if (e == null) None else Some(e.fold(identity, identity))
+  }
+
+  private[sbt] class Cache {
+    private[this] val underlying = new java.util.HashMap[Path, Either[FileStamp, FileStamp]]
+
+    /**
+     * Invalidate the cache entry, but don't re-stamp the file until it's actually used
+     * in a call to get or update.
+     *
+     * @param path the file whose stamp we are invalidating
+     */
+    def invalidate(path: Path): Unit = underlying.get(path) match {
+      case Right(s) =>
+        underlying.put(path, Left(s))
+        ()
+      case _ => ()
+    }
+    def get(path: Path): Option[FileStamp] =
+      underlying.get(path) match {
+        case null     => None
+        case Left(v)  => updateImpl(path, fileStampToStamper(v))
+        case Right(v) => Some(v)
+      }
+    def getOrElseUpdate(path: Path, stamper: FileStamper): Option[FileStamp] =
+      underlying.get(path) match {
+        case null     => updateImpl(path, stamper)
+        case Left(v)  => updateImpl(path, stamper)
+        case Right(v) => Some(v)
+      }
+    def remove(key: Path): Option[FileStamp] = {
+      underlying.remove(key).value
+    }
+    def put(key: Path, fileStamp: FileStamp): Option[FileStamp] =
+      underlying.put(key, Right(fileStamp)) match {
+        case null => None
+        case e    => e.value
+      }
+    def update(key: Path, stamper: FileStamper): (Option[FileStamp], Option[FileStamp]) = {
+      underlying.get(key) match {
+        case null => (None, updateImpl(key, stamper))
+        case v    => (v.value, updateImpl(key, stamper))
+      }
+    }
+
+    private def fileStampToStamper(stamp: FileStamp): FileStamper = stamp match {
+      case _: Hash => FileStamper.Hash
+      case _       => FileStamper.LastModified
+    }
+
+    private def updateImpl(path: Path, stamper: FileStamper): Option[FileStamp] = {
+      val stamp = FileStamp(path, stamper)
+      stamp match {
+        case None    => underlying.remove(path)
+        case Some(s) => underlying.put(path, Right(s))
+      }
+      stamp
+    }
+
+  }
 }

main/src/main/scala/sbt/nio/Keys.scala

@@ -9,6 +9,7 @@ package sbt.nio
 
 import java.io.InputStream
 import java.nio.file.Path
+import java.util.concurrent.atomic.AtomicBoolean
 
 import sbt.BuildSyntax.{ settingKey, taskKey }
 import sbt.KeyRanks.{ BMinusSetting, DSetting, Invisible }
@@ -22,6 +23,10 @@ import sbt.{ Def, InputKey, State, StateTransform }
 import scala.concurrent.duration.FiniteDuration
 
 object Keys {
+  sealed trait WatchBuildSourceOption
+  case object IgnoreSourceChanges extends WatchBuildSourceOption
+  case object WarnOnSourceChanges extends WatchBuildSourceOption
+  case object ReloadOnSourceChanges extends WatchBuildSourceOption
   val allInputFiles =
     taskKey[Seq[Path]]("All of the file inputs for a task excluding directories and hidden files.")
   val changedInputFiles = taskKey[Option[ChangedFiles]]("The changed files for a task")
@@ -44,10 +49,17 @@ object Keys {
   val fileTreeView =
     taskKey[FileTreeView.Nio[FileAttributes]]("A view of the local file system tree")
 
+  val checkBuildSources =
+    taskKey[Unit]("Check if any meta build sources have changed").withRank(DSetting)
+
   // watch related settings
   val watchAntiEntropyRetentionPeriod = settingKey[FiniteDuration](
     "Wall clock Duration for which a FileEventMonitor will store anti-entropy events. This prevents spurious triggers when a task takes a long time to run. Higher values will consume more memory but make spurious triggers less likely."
   ).withRank(BMinusSetting)
+  val onChangedBuildSource = settingKey[WatchBuildSourceOption](
+    "Determines what to do if the sbt meta build sources have changed"
+  ).withRank(DSetting)
+
   val watchDeletionQuarantinePeriod = settingKey[FiniteDuration](
     "Period for which deletion events will be quarantined. This is to prevent spurious builds when a file is updated with a rename which manifests as a file deletion followed by a file creation. The higher this value is set, the longer the delay will be between a file deletion and a build trigger but the less likely it is for a spurious trigger."
   ).withRank(DSetting)
@@ -85,6 +97,9 @@ object Keys {
   val watchOnTermination = settingKey[(Watch.Action, String, Int, State) => State](
     "Transforms the state upon completion of a watch. The String argument is the command that was run during the watch. The Int parameter specifies how many times the command was run during the watch."
   ).withRank(DSetting)
+  val watchPersistFileStamps = settingKey[Boolean](
+    "Toggles whether or not the continuous build will reuse the file stamps computed in previous runs. Setting this to true decrease watch startup latency but could cause inconsistent results if many source files are concurrently modified."
+  ).withRank(DSetting)
   val watchStartMessage = settingKey[(Int, String, Seq[String]) => Option[String]](
     "The message to show when triggered execution waits for sources to change. The parameters are the current watch iteration count, the current project name and the tasks that are being run with each build."
   ).withRank(DSetting)
@@ -93,9 +108,6 @@ object Keys {
     "watch",
     "Watch a task (or multiple tasks) and rebuild when its file inputs change or user input is received. The semantics are more or less the same as the `~` command except that it cannot transform the state on exit. This means that it cannot be used to reload the build."
   ).withRank(DSetting)
-  val watchTrackMetaBuild = settingKey[Boolean](
-    s"Toggles whether or not changing the build files (e.g. **/*.sbt, project/**/*.{scala,java}) should automatically trigger a project reload"
-  ).withRank(DSetting)
   val watchTriggeredMessage = settingKey[(Int, Path, Seq[String]) => Option[String]](
     "The message to show before triggered execution executes an action after sources change. The parameters are the path that triggered the build and the current watch iteration count."
   ).withRank(DSetting)
@@ -116,8 +128,6 @@ object Keys {
     taskKey[Seq[DynamicInput]]("The transitive inputs and triggers for a key").withRank(Invisible)
   private[sbt] val dynamicFileOutputs =
     taskKey[Seq[Path]]("The outputs of a task").withRank(Invisible)
-  private[sbt] val autoClean =
-    taskKey[Unit]("Automatically clean up a task returning file or path").withRank(Invisible)
 
   private[sbt] val inputFileStamps =
     taskKey[Seq[(Path, FileStamp)]]("Retrieves the hashes for a set of task input files")
@@ -126,16 +136,25 @@ object Keys {
     taskKey[Seq[(Path, FileStamp)]]("Retrieves the hashes for a set of task output files")
       .withRank(Invisible)
   private[sbt] type FileAttributeMap =
-    java.util.HashMap[Path, FileStamp]
+    java.util.Map[Path, FileStamp]
-  private[sbt] val persistentFileAttributeMap =
+  private[sbt] val persistentFileStampCache =
-    AttributeKey[FileAttributeMap]("persistent-file-attribute-map", Int.MaxValue)
+    AttributeKey[FileStamp.Cache]("persistent-file-stamp-cache", Int.MaxValue)
   private[sbt] val allInputPathsAndAttributes =
     taskKey[Seq[(Path, FileAttributes)]]("Get all of the file inputs for a task")
       .withRank(Invisible)
-  private[sbt] val fileAttributeMap = taskKey[FileAttributeMap](
+  private[sbt] val fileStampCache = taskKey[FileStamp.Cache](
     "Map of file stamps that may be cleared between task evaluation runs."
   ).withRank(Invisible)
-  private[sbt] val pathToFileStamp = taskKey[Path => FileStamp](
+  private[sbt] val pathToFileStamp = taskKey[Path => Option[FileStamp]](
     "A function that computes a file stamp for a path. It may have the side effect of updating a cache."
   ).withRank(Invisible)
+
+  private[this] val hasCheckedMetaBuildMsg =
+    "Indicates whether or not we have called the checkBuildSources task. This is to avoid warning " +
+      "user about build source changes if the build sources were changed while sbt was shutdown. " +
+      " When that occurs, the previous cache reflects the state of the old build files, but by " +
+      " the time the checkBuildSources task has run, the build will have already been loaded with the " +
+      " new meta build sources so we should neither warn the user nor automatically restart the build"
+  private[sbt] val hasCheckedMetaBuild =
+    AttributeKey[AtomicBoolean]("has-checked-meta-build", hasCheckedMetaBuildMsg, Int.MaxValue)
 }

main/src/main/scala/sbt/nio/Settings.scala

@@ -142,8 +142,6 @@ private[sbt] object Settings {
       case dynamicDependency.key => (dynamicDependency in scopedKey.scope := { () }) :: Nil
       case transitiveClasspathDependency.key =>
         (transitiveClasspathDependency in scopedKey.scope := { () }) :: Nil
-      case allInputFiles.key     => allFilesImpl(scopedKey) :: Nil
-      case changedInputFiles.key => changedInputFilesImpl(scopedKey)
       case changedOutputFiles.key =>
         changedFilesImpl(scopedKey, changedOutputFiles, outputFileStamps)
       case pathToFileStamp.key => stamper(scopedKey) :: Nil
@@ -198,7 +196,7 @@ private[sbt] object Settings {
       val inputs = (fileInputs in scopedKey.scope).value
       val stamper = (inputFileStamper in scopedKey.scope).value
       val forceTrigger = (watchForceTriggerOnAnyChange in scopedKey.scope).value
-      val dynamicInputs = Continuous.dynamicInputs.value
+      val dynamicInputs = (Continuous.dynamicInputs in scopedKey.scope).value
       // This makes watch work by ensuring that the input glob is registered with the
       // repository used by the watch process.
       sbt.Keys.state.value.get(globalFileTreeRepository).foreach { repo =>
@@ -206,7 +204,8 @@ private[sbt] object Settings {
       }
       dynamicInputs.foreach(_ ++= inputs.map(g => DynamicInput(g, stamper, forceTrigger)))
       view.list(inputs)
-    }) :: fileStamps(scopedKey) :: allFilesImpl(scopedKey) :: Nil
+    }) :: fileStamps(scopedKey) :: allFilesImpl(scopedKey) :: Nil ++
+      changedInputFilesImpl(scopedKey)
   }
 
   private[this] val taskClass = classOf[Task[_]]
@@ -320,8 +319,9 @@ private[sbt] object Settings {
   private[sbt] def fileStamps(scopedKey: Def.ScopedKey[_]): Def.Setting[_] =
     addTaskDefinition(Keys.inputFileStamps in scopedKey.scope := {
       val stamper = (Keys.pathToFileStamp in scopedKey.scope).value
-      (Keys.allInputPathsAndAttributes in scopedKey.scope).value.collect {
+      (Keys.allInputPathsAndAttributes in scopedKey.scope).value.flatMap {
-        case (p, a) if a.isRegularFile && !Files.isHidden(p) => p -> stamper(p)
+        case (p, a) if a.isRegularFile && !Files.isHidden(p) => stamper(p).map(p -> _)
+        case _                                               => None
       }
     })
   private[this] def outputsAndStamps[T: JsonFormat: ToSeqPath](
@@ -341,11 +341,11 @@ private[sbt] object Settings {
     })
   private[this] def outputFileStampsImpl(scope: Scope): Def.Setting[_] =
     addTaskDefinition(outputFileStamps in scope := {
-      val stamper: Path => FileStamp = (outputFileStamper in scope).value match {
+      val stamper: Path => Option[FileStamp] = (outputFileStamper in scope).value match {
         case LastModified => FileStamp.lastModified
         case Hash         => FileStamp.hash
       }
-      (allOutputFiles in scope).value.map(p => p -> stamper(p))
+      (allOutputFiles in scope).value.flatMap(p => stamper(p).map(p -> _))
     })
 
   /**
@@ -357,18 +357,8 @@ private[sbt] object Settings {
    */
   private[this] def stamper(scopedKey: Def.ScopedKey[_]): Def.Setting[_] =
     addTaskDefinition((Keys.pathToFileStamp in scopedKey.scope) := {
-      val attributeMap = Keys.fileAttributeMap.value
+      val attributeMap = Keys.fileStampCache.value
       val stamper = (Keys.inputFileStamper in scopedKey.scope).value
-      path: Path =>
+      path: Path => attributeMap.getOrElseUpdate(path, stamper)
-        attributeMap.get(path) match {
-          case null =>
-            val stamp = stamper match {
-              case Hash         => FileStamp.hash(path)
-              case LastModified => FileStamp.lastModified(path)
-            }
-            attributeMap.put(path, stamp)
-            stamp
-          case s => s
-        }
     })
 }

main/src/main/scala/sbt/nio/Watch.scala

@@ -110,7 +110,7 @@ object Watch {
       override val occurredAt: FiniteDuration
   ) extends Event
       with Event.Impl {
-    override def toString: String = s"Update(path, ${occurredAt.toEpochString})"
+    override def toString: String = s"Update($path, ${occurredAt.toEpochString})"
   }
   object Update {
     def apply(event: FileEvent[FileAttributes]): Update =
@@ -217,7 +217,7 @@ object Watch {
    * Action that indicates that an error has occurred. The watch will be terminated when this action
    * is produced.
    */
-  final class HandleError(val throwable: Throwable) extends CancelWatch {
+  sealed class HandleError(val throwable: Throwable) extends CancelWatch {
     override def equals(o: Any): Boolean = o match {
       case that: HandleError => this.throwable == that.throwable
       case _                 => false
@@ -226,6 +226,15 @@ object Watch {
     override def toString: String = s"HandleError($throwable)"
   }
 
+  /**
+   * Action that indicates that an error has occurred. The watch will be terminated when this action
+   * is produced.
+   */
+  private[sbt] final class HandleUnexpectedError(override val throwable: Throwable)
+      extends HandleError(throwable) {
+    override def toString: String = s"HandleUnexpectedError($throwable)"
+  }
+
   /**
    * Action that indicates that the watch should continue as though nothing happened. This may be
    * because, for example, no user input was yet available.
@@ -236,7 +245,7 @@ object Watch {
    * Action that indicates that the watch should pause while the build is reloaded. This is used to
    * automatically reload the project when the build files (e.g. build.sbt) are changed.
    */
-  case object Reload extends CancelWatch
+  private[sbt] case object Reload extends CancelWatch
 
   /**
    * Action that indicates that we should exit and run the provided command.
@@ -279,7 +288,12 @@ object Watch {
   def apply(task: () => Unit, onStart: NextAction, nextAction: NextAction): Watch.Action = {
     def safeNextAction(delegate: NextAction): Watch.Action =
       try delegate()
-      catch { case NonFatal(t) => new HandleError(t) }
+      catch {
+        case NonFatal(t) =>
+          System.err.println(s"Watch caught unexpected error:")
+          t.printStackTrace(System.err)
+          new HandleError(t)
+      }
     @tailrec def next(): Watch.Action = safeNextAction(nextAction) match {
       // This should never return Ignore due to this condition.
       case Ignore => next()
@@ -379,11 +393,10 @@ object Watch {
 
   private[this] val options = {
     val enter = "<enter>"
-    val newLine = if (Util.isWindows) enter else ""
     val opts = Seq(
       s"$enter: return to the shell",
-      s"'r$newLine': repeat the current command",
+      s"'r': repeat the current command",
-      s"'x$newLine': exit sbt"
+      s"'x': exit sbt"
     )
     s"Options:\n${opts.mkString("  ", "\n  ", "")}"
   }

main/src/test/scala/sbt/WatchSpec.scala

@@ -15,10 +15,10 @@ import org.scalatest.{ FlatSpec, Matchers }
 import sbt.WatchSpec._
 import sbt.internal.nio.{ FileEvent, FileEventMonitor, FileTreeRepository }
 import sbt.io._
-import sbt.io.syntax._
 import sbt.nio.Watch
 import sbt.nio.Watch.{ NullLogger, _ }
-import sbt.nio.file.{ FileAttributes, Glob }
+import sbt.nio.file.{ FileAttributes, Glob, RecursiveGlob }
+import sbt.nio.file.syntax._
 import sbt.util.Logger
 
 import scala.collection.mutable
@@ -84,13 +84,13 @@ class WatchSpec extends FlatSpec with Matchers {
   }
   "Watch" should "stop" in IO.withTemporaryDirectory { dir =>
     val task = new Task
-    watch(task, TestDefaults.callbacks(inputs = Seq(dir.toRealPath ** AllPassFilter))) shouldBe CancelWatch
+    watch(task, TestDefaults.callbacks(inputs = Seq(dir.toRealPath.toGlob / RecursiveGlob))) shouldBe CancelWatch
   }
   it should "trigger" in IO.withTemporaryDirectory { dir =>
     val triggered = new AtomicBoolean(false)
     val task = new Task
     val callbacks = TestDefaults.callbacks(
-      inputs = Seq(dir.toRealPath ** AllPassFilter),
+      inputs = Seq(dir.toRealPath.toGlob / RecursiveGlob),
       onStartWatch = () => if (task.getCount == 2) CancelWatch else Ignore,
       onWatchEvent = _ => { triggered.set(true); Trigger },
       watchingMessage = () => {
@@ -107,7 +107,7 @@ class WatchSpec extends FlatSpec with Matchers {
     val bar = realDir.toPath.resolve("bar")
     val task = new Task
     val callbacks = TestDefaults.callbacks(
-      inputs = Seq(realDir ** AllPassFilter),
+      inputs = Seq(realDir.toGlob / RecursiveGlob),
       onStartWatch = () => if (task.getCount == 2) CancelWatch else Ignore,
       onWatchEvent = e => if (e.path == foo) Trigger else Ignore,
       triggeredMessage = e => { queue += e.path; None },
@@ -126,7 +126,7 @@ class WatchSpec extends FlatSpec with Matchers {
     val bar = realDir.toPath.resolve("bar")
     val task = new Task
     val callbacks = TestDefaults.callbacks(
-      inputs = Seq(realDir ** AllPassFilter),
+      inputs = Seq(realDir.toGlob / RecursiveGlob),
       onStartWatch = () => if (task.getCount == 3) CancelWatch else Ignore,
       onWatchEvent = e => if (e.path != realDir.toPath) Trigger else Ignore,
       triggeredMessage = e => { queue += e.path; None },
@@ -148,19 +148,19 @@ class WatchSpec extends FlatSpec with Matchers {
     val exception = new IllegalStateException("halt")
     val task = new Task { override def apply(): Unit = throw exception }
     val callbacks = TestDefaults.callbacks(
-      Seq(dir.toRealPath ** AllPassFilter),
+      Seq(dir.toRealPath.toGlob / RecursiveGlob),
     )
     watch(task, callbacks) shouldBe new HandleError(exception)
   }
   it should "reload" in IO.withTemporaryDirectory { dir =>
     val task = new Task
     val callbacks = TestDefaults.callbacks(
-      inputs = Seq(dir.toRealPath ** AllPassFilter),
+      inputs = Seq(dir.toRealPath.toGlob / RecursiveGlob),
       onStartWatch = () => Ignore,
-      onWatchEvent = _ => Reload,
+      onWatchEvent = _ => Watch.Reload,
       watchingMessage = () => { new File(dir, "file").createNewFile(); None }
     )
-    watch(task, callbacks) shouldBe Reload
+    watch(task, callbacks) shouldBe Watch.Reload
   }
 }
 

main/src/test/scala/sbt/internal/FileStampJsonSpec.scala

@@ -45,6 +45,6 @@ class FileStampJsonSpec extends FlatSpec {
     val both: Seq[(Path, FileStamp)] = hashes ++ lastModifiedTimes
     val json = Converter.toJsonUnsafe(both)(fileStampJsonFormatter)
     val deserialized = Converter.fromJsonUnsafe(json)(fileStampJsonFormatter)
-    assert(both.sameElements(deserialized))
+    assert(both == deserialized)
   }
 }

project/Dependencies.scala

@@ -9,7 +9,7 @@ object Dependencies {
   val baseScalaVersion = scala212
 
   // sbt modules
-  private val ioVersion = "1.3.0-M9"
+  private val ioVersion = "1.3.0-M10"
   private val utilVersion = "1.3.0-M6"
   private val lmVersion =
     sys.props.get("sbt.build.lm.version") match {

sbt/src/sbt-test/actions/clean-keep/build.sbt

@@ -5,6 +5,6 @@ cleanKeepFiles ++= Seq(
 	target.value / "keepfile"
 )
 
-cleanKeepGlobs += target.value / "keepdir" ** AllPassFilter
+cleanKeepGlobs += target.value.toGlob / "keepdir" / **
 // This is necessary because recursive globs do not include the base directory.
 cleanKeepGlobs += Glob(target.value / "keepdir")

sbt/src/sbt-test/nio/file-hashes/build.sbt

@@ -2,8 +2,8 @@ import sbt.nio.Keys._
 
 val foo = taskKey[Unit]("foo")
 foo / fileInputs := Seq(
-  (baseDirectory.value / "base").toGlob / "*.md",
+  baseDirectory.value.toGlob / "base" / "*.md",
-  (baseDirectory.value / "base").toGlob / "*.txt",
+  baseDirectory.value.toGlob / "base" / "*.txt",
 )
 
 val checkModified = taskKey[Unit]("check that modified files are returned")

sbt/src/sbt-test/nio/glob-dsl/build.sbt

@@ -3,7 +3,7 @@
 // Check that we can correctly extract Foo.txt with a recursive source
 val foo = taskKey[Seq[File]]("Retrieve Foo.txt")
 
-foo / fileInputs += baseDirectory.value ** "*.txt"
+foo / fileInputs += baseDirectory.value.toGlob / ** / "*.txt"
 
 foo := (foo / allInputFiles).value.map(_.toFile)
 
@@ -14,24 +14,24 @@ checkFoo := assert(foo.value == Seq(baseDirectory.value / "base/subdir/nested-su
 // Check that we can correctly extract Bar.md with a non-recursive source
 val bar = taskKey[Seq[File]]("Retrieve Bar.md")
 
-bar / fileInputs += baseDirectory.value / "base/subdir/nested-subdir" * "*.md"
+bar / fileInputs += baseDirectory.value.toGlob / "base" / "subdir" / "nested-subdir" / "*.md"
 
 bar := (bar / allInputFiles).value.map(_.toFile)
 
 val checkBar = taskKey[Unit]("Check that the Bar.md file is retrieved")
 
-checkBar := assert(bar.value == Seq(baseDirectory.value / "base/subdir/nested-subdir/Bar.md"))
+checkBar := assert(bar.value == Seq(baseDirectory.value / "base" / "subdir" / "nested-subdir" / "Bar.md"))
 
 // Check that we can correctly extract Bar.md and Foo.md with a non-recursive source
 val all = taskKey[Seq[File]]("Retrieve all files")
 
-all / fileInputs += baseDirectory.value / "base" / "subdir" / "nested-subdir" * AllPassFilter
+all / fileInputs += baseDirectory.value.toGlob / "base" / "subdir" / "nested-subdir" / *
 
 val checkAll = taskKey[Unit]("Check that the Bar.md file is retrieved")
 
 checkAll := {
   import sbt.dsl.LinterLevel.Ignore
-  val expected = Set("Foo.txt", "Bar.md").map(baseDirectory.value / "base/subdir/nested-subdir" / _)
+  val expected = Set("Foo.txt", "Bar.md").map(baseDirectory.value / "base" / "subdir" / "nested-subdir" / _)
   val actual = (all / allInputFiles).value.map(_.toFile).toSet
   assert(actual == expected)
 }
@@ -39,8 +39,8 @@ checkAll := {
 val set = taskKey[Seq[File]]("Specify redundant sources in a set")
 
 set / fileInputs ++= Seq(
-  baseDirectory.value / "base" ** -DirectoryFilter,
+  baseDirectory.value.toGlob / "base" / **,
-  baseDirectory.value / "base" / "subdir" / "nested-subdir" * -DirectoryFilter
+  baseDirectory.value.toGlob / "base" / "subdir" / "nested-subdir" / *
 )
 
 val depth = taskKey[Seq[File]]("Specify redundant sources with limited depth")

sbt/src/sbt-test/nio/intraproject-inputs/project/Build.scala

@@ -21,7 +21,7 @@ object Build {
       (Compile / unmanagedResources / fileInputs).value,
     Test / cached / fileInputs := (Test / unmanagedSources / fileInputs).value ++
       (Test / unmanagedResources / fileInputs).value,
-    Compile / newInputs / fileInputs += baseDirectory.value * "*.sc",
+    Compile / newInputs / fileInputs += baseDirectory.value.toGlob / "*.sc",
     Compile / unmanagedSources / fileInputs ++= (Compile / newInputs / fileInputs).value,
     checkCompile := {
       val actual = (Compile / compile / transitiveDynamicInputs).value.map(_.glob).toSet

sbt/src/sbt-test/nio/reload/build.sbt

@@ -0,0 +1,4 @@
+val foo = taskKey[Unit]("working task")
+foo := { println("foo") }
+
+Global / onChangedBuildSource := ReloadOnSourceChanges

sbt/src/sbt-test/nio/reload/changes/broken.sbt

@@ -0,0 +1,4 @@
+val foo = taskKey[Unit]("broken task")
+foo := { throw new IllegalStateException("foo") }
+
+Global / onChangedBuildSource := ReloadOnSourceChanges

sbt/src/sbt-test/nio/reload/changes/working.sbt

@@ -0,0 +1,4 @@
+val foo = taskKey[Unit]("working task")
+foo := { println("foo") }
+
+Global / onChangedBuildSource := ReloadOnSourceChanges

sbt/src/sbt-test/nio/reload/test

@@ -0,0 +1,9 @@
+> foo
+
+$ copy-file changes/broken.sbt build.sbt
+
+-> foo
+
+$ copy-file changes/working.sbt build.sbt
+
+> foo

sbt/src/sbt-test/watch/command-parser/build.sbt

@@ -8,6 +8,6 @@ setStringValue := setStringValueImpl.evaluated
 
 checkStringValue := checkStringValueImpl.evaluated
 
-setStringValue / watchTriggers := baseDirectory.value * "string.txt" :: Nil
+setStringValue / watchTriggers := baseDirectory.value.toGlob / "string.txt" :: Nil
 
 watchOnFileInputEvent := { (_, _) => sbt.nio.Watch.CancelWatch }

sbt/src/sbt-test/watch/custom-config/project/Build.scala

@@ -18,7 +18,7 @@ object Build {
   }
   lazy val foo = project.settings(
     watchStartMessage := { (count: Int, _, _) => Some(s"FOO $count") },
-    Compile / compile / watchTriggers += baseDirectory.value * "foo.txt",
+    Compile / compile / watchTriggers += baseDirectory.value.toGlob / "foo.txt",
     Compile / compile / watchStartMessage := { (count: Int, _, _) =>
       // this checks that Compile / compile / watchStartMessage
       // is preferred to Compile / watchStartMessage
@@ -35,7 +35,9 @@ object Build {
     checkStringValue := checkStringValueImpl.evaluated,
     watchOnFileInputEvent := { (_, _) => Watch.CancelWatch }
   )
-  lazy val bar = project.settings(fileInputs in setStringValue += baseDirectory.value * "foo.txt")
+  lazy val bar = project.settings(
+    fileInputs in setStringValue += baseDirectory.value.toGlob / "foo.txt"
+  )
   lazy val root = (project in file(".")).aggregate(foo, bar).settings(
     watchOnFileInputEvent := { (_, _) => Watch.CancelWatch }
   )

sbt/src/sbt-test/watch/dynamic-inputs/project/Build.scala

@@ -23,7 +23,7 @@ object Build {
   }
   lazy val root = (project in file(".")).settings(
     reloadFile := baseDirectory.value / "reload",
-    foo / fileInputs += baseDirectory.value * "foo.txt",
+    foo / fileInputs += baseDirectory.value.toGlob / "foo.txt",
     foo := (foo / allInputFiles).value,
     setStringValue := Def.taskDyn {
       // This hides foo / fileInputs from the input graph

sbt/src/sbt-test/watch/file-input-aggregation/build.sbt

@@ -4,4 +4,4 @@ val root = Build.root
 val foo = Build.foo
 val bar = Build.bar
 
-Global / watchTriggers += baseDirectory.value * "baz.txt"
+Global / watchTriggers += baseDirectory.value.toGlob / "baz.txt"

sbt/src/sbt-test/watch/file-input-aggregation/project/Build.scala

@@ -46,14 +46,14 @@ object Build {
       },
       checkTriggers := {
         val actual = triggers((Compile / compile / transitiveDynamicInputs).value).toSet
-        val base = baseDirectory.value.getParentFile
+        val base = baseDirectory.value.getParentFile.toGlob
         // This checks that since foo depends on bar there is a transitive trigger generated
         // for the "bar.txt" trigger added to bar / Compile / unmanagedResources (which is a
         // transitive dependency of
-        val expected: Set[Glob] = Set(base * "baz.txt", (base / "bar") * "bar.txt")
+        val expected: Set[Glob] = Set(base / "baz.txt", base / "bar" / "bar.txt")
         assert(actual == expected)
       },
-      Test / test / watchTriggers += (baseDirectory.value / "test.txt").toGlob,
+      Test / test / watchTriggers += baseDirectory.value.toGlob / "test.txt",
       Test / checkTriggers := {
         val testTriggers = triggers((Test / test / transitiveDynamicInputs).value).toSet
         // This validates that since the "test.txt" trigger is only added to the Test / test task,
@@ -61,34 +61,34 @@ object Build {
         // are found in the test above for the compile configuration because of the transitive
         // classpath dependency that is added in Defaults.internalDependencies.
         val compileTriggers = triggers((Test / compile / transitiveDynamicInputs).value).toSet
-        val base = baseDirectory.value.getParentFile
+        val base = baseDirectory.value.getParentFile.toGlob
         val expected: Set[Glob] =
-          Set(base * "baz.txt", (base / "bar") * "bar.txt", (base / "foo") * "test.txt")
+          Set(base / "baz.txt", base / "bar" / "bar.txt", base / "foo" / "test.txt")
         assert(testTriggers == expected)
-        assert((testTriggers - ((base / "foo") * "test.txt")) == compileTriggers)
+        assert((testTriggers - (base / "foo" / "test.txt")) == compileTriggers)
       },
     )
     .dependsOn(bar)
 
   lazy val bar = project.settings(
-    fileInputs in setStringValue += baseDirectory.value * "foo.txt",
+    fileInputs in setStringValue += baseDirectory.value.toGlob / "foo.txt",
-    setStringValue / watchTriggers += baseDirectory.value * "bar.txt",
+    setStringValue / watchTriggers += baseDirectory.value.toGlob / "bar.txt",
     // This trigger should transitively propagate to foo / compile and foo / Test / compile
-    Compile / unmanagedResources / watchTriggers += baseDirectory.value * "bar.txt",
+    Compile / unmanagedResources / watchTriggers += baseDirectory.value.toGlob / "bar.txt",
     checkTriggers := {
-      val base = baseDirectory.value.getParentFile
+      val base = baseDirectory.value.getParentFile.toGlob
       val actual = triggers((Compile / compile / transitiveDynamicInputs).value).toSet
-      val expected: Set[Glob] = Set((base / "bar") * "bar.txt", base * "baz.txt")
+      val expected: Set[Glob] = Set(base / "bar" / "bar.txt", base / "baz.txt")
       assert(actual == expected)
     },
     // This trigger should not transitively propagate to any foo task
-    Test / unmanagedResources / watchTriggers += baseDirectory.value * "bar-test.txt",
+    Test / unmanagedResources / watchTriggers += baseDirectory.value.toGlob / "bar-test.txt",
     Test / checkTriggers := {
       val testTriggers = triggers((Test / test / transitiveDynamicInputs).value).toSet
       val compileTriggers = triggers((Test / compile / transitiveDynamicInputs).value).toSet
-      val base = baseDirectory.value.getParentFile
+      val base = baseDirectory.value.getParentFile.toGlob
       val expected: Set[Glob] =
-        Set(base * "baz.txt", (base / "bar") * "bar.txt", (base / "bar") * "bar-test.txt")
+        Set(base / "baz.txt", base / "bar" / "bar.txt", base / "bar" / "bar-test.txt")
       assert(testTriggers == expected)
       assert(testTriggers == compileTriggers)
     },
@@ -101,7 +101,7 @@ object Build {
       },
       checkTriggers := {
         val actual = triggers((Compile / compile / transitiveDynamicInputs).value)
-        val expected: Seq[Glob] = baseDirectory.value * "baz.txt" :: Nil
+        val expected: Seq[Glob] = baseDirectory.value.toGlob / "baz.txt" :: Nil
         assert(actual == expected)
       },
     )

sbt/src/sbt-test/watch/on-change/build.sbt

@@ -0,0 +1,36 @@
+import java.nio.file._
+import sbt.nio.Keys._
+import sbt.nio._
+import scala.concurrent.duration._
+import StandardCopyOption.{ REPLACE_EXISTING => replace }
+
+watchTriggeredMessage := { (i, path: Path, c) =>
+  val prev = watchTriggeredMessage.value
+  if (path.getFileName.toString == "C.scala")
+    throw new IllegalStateException("C.scala should not trigger")
+  prev(i, path, c)
+}
+
+watchOnIteration := { i: Int =>
+  val base = baseDirectory.value.toPath
+  val src =
+    base.resolve("src").resolve("main").resolve("scala").resolve("sbt").resolve("test")
+  val changes = base.resolve("changes")
+  Files.copy(changes.resolve("C.scala"), src.resolve("C.scala"), replace)
+  if (i < 5) {
+    val content =
+      new String(Files.readAllBytes(changes.resolve("A.scala"))) + "\n" + ("//" * i)
+    Files.write(src.resolve("A.scala"), content.getBytes)
+  } else {
+    Files.copy(changes.resolve("B.scala"), src.resolve("B.scala"), replace)
+  }
+  println(s"Waiting for changes...")
+  Watch.Ignore
+}
+
+watchOnFileInputEvent := { (_, event: Watch.Event) =>
+  if (event.path.getFileName.toString == "B.scala") Watch.CancelWatch
+  else Watch.Trigger
+}
+
+watchAntiEntropy := 0.millis

sbt/src/sbt-test/watch/on-change/changes/A.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class A

sbt/src/sbt-test/watch/on-change/changes/B.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class B

sbt/src/sbt-test/watch/on-change/changes/C.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class C

sbt/src/sbt-test/watch/on-change/src/main/scala/sbt/test/A.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class A {

sbt/src/sbt-test/watch/on-change/src/main/scala/sbt/test/B.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class B {

sbt/src/sbt-test/watch/on-change/src/main/scala/sbt/test/C.scala

@@ -0,0 +1,3 @@
+package sbt.test
+
+class C

sbt/src/sbt-test/watch/on-change/test

@@ -0,0 +1,3 @@
+> ~compile
+
+> compile

sbt/src/sbt-test/watch/on-start-watch/build.sbt

@@ -5,7 +5,7 @@ val resetCount = taskKey[Unit]("reset compile count")
 checkCount := {
   val expected = Def.spaceDelimited().parsed.head.toInt
   if (Count.get != expected)
-    throw new IllegalStateException(s"Expected ${expected} compilation runs, got ${Count.get}")
+    throw new IllegalStateException(s"Expected $expected compilation runs, got ${Count.get}")
 }
 
 resetCount := {
@@ -16,9 +16,4 @@ failingTask := {
   throw new IllegalStateException("failed")
 }
 
-Compile / compile := {
+onChangedBuildSource := ReloadOnSourceChanges
-  Count.increment()
-  // Trigger a new build by updating the last modified time
-  ((Compile / scalaSource).value / "A.scala").setLastModified(5000)
-  (Compile / compile).value
-}

sbt/src/sbt-test/watch/on-start-watch/changes/extra.sbt

@@ -2,3 +2,11 @@ val checkReloaded = taskKey[Unit]("Asserts that the build was reloaded")
 checkReloaded := { () }
 
 watchOnIteration := { _ => sbt.nio.Watch.CancelWatch }
+
+Compile / compile := {
+  Count.increment()
+  // Trigger a new build by updating the last modified time
+  val file = (Compile / scalaSource).value / "A.scala"
+  IO.write(file, IO.read(file) + ("\n" * Count.get))
+  (Compile / compile).value
+}

sbt/src/sbt-test/watch/on-start-watch/extra.sbt

@@ -1 +1,7 @@
-watchOnIteration := { _ => sbt.nio.Watch.Reload }
+Compile / compile := {
+  Count.increment()
+  // Trigger a new build by updating the last modified time
+  val extra = baseDirectory.value / "extra.sbt"
+  IO.copyFile(baseDirectory.value / "changes" / "extra.sbt", extra, CopyOptions().withOverwrite(true))
+  (Compile / compile).value
+}

sbt/src/sbt-test/watch/on-start-watch/test

@@ -1,6 +1,3 @@
-# verify that reloading occurs if watchOnStart returns Watch.Reload
-$ copy-file changes/extra.sbt extra.sbt
-
 > ~compile
 > checkReloaded
 

sbt/src/sbt-test/watch/on-termination/project/Build.scala

@@ -19,7 +19,7 @@ object Build {
   }
   lazy val root = (project in file(".")).settings(
     reloadFile := baseDirectory.value / "reload",
-    setStringValue / watchTriggers += baseDirectory.value * "foo.txt",
+    setStringValue / watchTriggers += baseDirectory.value.toGlob / "foo.txt",
     setStringValue := setStringValueImpl.evaluated,
     checkStringValue := checkStringValueImpl.evaluated,
     watchOnFileInputEvent := { (_, _) => Watch.CancelWatch },

sbt/src/sbt-test/watch/task/changes/Build.scala

@@ -17,7 +17,7 @@ object Build {
     assert(IO.read(file(stringFile)) == string)
   }
   lazy val root = (project in file(".")).settings(
-    setStringValue / watchTriggers += baseDirectory.value * "foo.txt",
+    setStringValue / watchTriggers += baseDirectory.value.toGlob / "foo.txt",
     setStringValue := setStringValueImpl.evaluated,
     checkStringValue := checkStringValueImpl.evaluated,
     watchStartMessage := { (_, _, _) =>

sbt/src/sbt-test/watch/task/project/Build.scala

@@ -19,7 +19,7 @@ object Build {
   }
   lazy val root = (project in file(".")).settings(
     reloadFile := baseDirectory.value / "reload",
-    setStringValue / watchTriggers += baseDirectory.value * "foo.txt",
+    setStringValue / watchTriggers += baseDirectory.value.toGlob / "foo.txt",
     setStringValue := setStringValueImpl.evaluated,
     checkStringValue := checkStringValueImpl.evaluated,
     watchStartMessage := { (_, _, _) =>

scripted-sbt-redux/src/main/scala/sbt/scriptedtest/ScriptedTests.scala

@@ -129,13 +129,16 @@ final class ScriptedTests(
         case s => s
       }
 
-      val (launcherBasedTests, runFromSourceBasedTests) = labelsAndDirs.partition {
+      val (launcherBasedTestsUnfiltered, runFromSourceBasedTestsUnfiltered) =
-        case (testName, _) =>
+        labelsAndDirs.partition {
-          determineRemoteSbtCreatorKind(testName) match {
+          case (testName, _) =>
-            case RemoteSbtCreatorKind.LauncherBased      => true
+            determineRemoteSbtCreatorKind(testName) match {
-            case RemoteSbtCreatorKind.RunFromSourceBased => false
+              case RemoteSbtCreatorKind.LauncherBased      => true
-          }
+              case RemoteSbtCreatorKind.RunFromSourceBased => false
-      }
+            }
+        }
+      val launcherBasedTests = launcherBasedTestsUnfiltered.filterNot(windowsExclude)
+      val runFromSourceBasedTests = runFromSourceBasedTestsUnfiltered.filterNot(windowsExclude)
 
       def logTests(size: Int, how: String) =
         log.info(
@@ -163,6 +166,17 @@ final class ScriptedTests(
     }
   }
 
+  private[this] val windowsExclude: (((String, String), File)) => Boolean =
+    if (scala.util.Properties.isWin) {
+      case (testName, _) =>
+        testName match {
+          case ("classloader-cache", "jni") => true // no native lib is built for windows
+          case ("classloader-cache", "snapshot") =>
+            true // the test overwrites a jar that is being used which is verboten in windows
+          case ("nio", "make-clone") => true // uses gcc which isn't set up on all systems
+          case _                     => false
+        }
+    } else _ => false
   private def determineRemoteSbtCreatorKind(testName: (String, String)): RemoteSbtCreatorKind = {
     import RemoteSbtCreatorKind._
     val (group, name) = testName