New WatchService based on Java 7's WatchService

.travis.yml

@@ -3,6 +3,6 @@ scala:
    - 2.10.6
    - 2.11.11
    - 2.12.2
-
+   - 2.13.0-M1
 jdk:
   - oraclejdk8

build.sbt

@@ -1,7 +1,7 @@
 import Dependencies._
 // import com.typesafe.tools.mima.core._, ProblemFilters._
 
-def baseVersion: String = "1.0.0-M8"
+def baseVersion: String = "1.0.0-M12"
 
 def commonSettings: Seq[Setting[_]] = Seq(
   scalaVersion := scala212,

io/src/main/scala/sbt/internal/io/SourceModificationWatch.scala

@@ -3,45 +3,169 @@
  */
 package sbt.internal.io
 
-import annotation.tailrec
-import sbt.io.PathFinder
+import java.nio.file.{ Files, Path, WatchEvent, WatchKey }
+import java.nio.file.StandardWatchEventKinds._
+
+import sbt.io.{ DirectoryFilter, FileFilter, WatchService }
+import sbt.io.syntax._
+
+import scala.annotation.tailrec
 
 private[sbt] object SourceModificationWatch {
-  @tailrec def watch(sourcesFinder: PathFinder, pollDelayMillis: Int, state: WatchState)(terminationCondition: => Boolean): (Boolean, WatchState) =
-    {
-      import state._
-
-      val sourceFiles: Iterable[java.io.File] = sourcesFinder.get
-      val sourceFilesPath: Set[String] = sourceFiles.map(_.getCanonicalPath)(collection.breakOut)
-      val lastModifiedTime =
-        (0L /: sourceFiles) { (acc, file) => math.max(acc, file.lastModified) }
-
-      val sourcesModified =
-        lastModifiedTime > lastCallbackCallTime ||
-          previousFiles != sourceFilesPath
-
-      val (triggered, newCallbackCallTime) =
-        if (sourcesModified)
-          (false, System.currentTimeMillis)
-        else
-          (awaitingQuietPeriod, lastCallbackCallTime)
-
-      val newState = new WatchState(newCallbackCallTime, sourceFilesPath, sourcesModified, if (triggered) count + 1 else count)
-      if (triggered)
-        (true, newState)
-      else {
-        Thread.sleep(pollDelayMillis.toLong)
-        if (terminationCondition)
-          (false, newState)
-        else
-          watch(sourcesFinder, pollDelayMillis, newState)(terminationCondition)
+
+  /**
+   * Checks for modifications on the file system every `delayMillis` milliseconds,
+   * until changes are detected or `terminationCondition` evaluates to `true`.
+   */
+  @tailrec
+  def watch(delayMillis: Long, state: WatchState)(terminationCondition: => Boolean): (Boolean, WatchState) = {
+    if (state.count == 0) (true, state.withCount(1))
+    else {
+      val events =
+        state.pollEvents().map(expandEvent)
+
+      if (events.isEmpty) {
+        if (terminationCondition) {
+          (false, state)
+        } else {
+          Thread.sleep(delayMillis)
+          watch(delayMillis, state)(terminationCondition)
+        }
+      } else {
+        val previousFiles = state.registered.keySet
+        val newFiles      = state.sources.flatMap(_.getUnfilteredPaths()).toSet
+        val createdFiles  = newFiles -- previousFiles
+        val deletedFiles  = previousFiles -- newFiles
+
+        // We may have events that are not relevant (e.g., created an empty directory.)
+        // We filter out those changes, so that we don't trigger unnecessarily.
+        val filteredDeleted = deletedFiles.filter(p => state.sources.exists(_.accept(p, false)))
+        val filteredCreated = createdFiles.filter(p => state.sources.exists(_.accept(p, false)))
+        val filteredModified = events.collect {
+          case (p, ENTRY_MODIFY) if state.sources.exists(_.accept(p, false)) => p
+        }
+
+        // Register and remove _unfiltered_ files. This is correct because directories
+        // are likely to be filtered out (for instance), but we should still add them
+        // to the files that are watched.
+        // We don't increment count because we don't know yet if we'll trigger.
+        val newState = state ++ createdFiles -- deletedFiles
+
+        if (filteredCreated.nonEmpty || filteredDeleted.nonEmpty || filteredModified.nonEmpty) {
+          (true, newState.withCount(newState.count + 1))
+        } else {
+          Thread.sleep(delayMillis)
+          watch(delayMillis, newState)(terminationCondition)
+        }
+      }
+    }
+  }
+
+  private def expandEvent(event: (Path, WatchEvent[_])): (Path, WatchEvent.Kind[Path]) = {
+    event match {
+      case (base, ev) =>
+        val fullPath = base.resolve(ev.context().asInstanceOf[Path])
+        val kind     = ev.kind().asInstanceOf[WatchEvent.Kind[Path]]
+        (fullPath, kind)
+    }
+  }
+}
+
+/** The state of the file watch. */
+final class WatchState private (
+  val count: Int,
+  private[sbt] val sources: Seq[Source],
+  service: WatchService,
+  private[sbt] val registered: Map[Path, WatchKey]
+) {
+  /** Removes all of `fs` from the watched paths. */
+  private[sbt] def --(fs: Iterable[Path]): WatchState = {
+    for { f  <- fs;
+          wk <- registered.get(f);
+          if (registered.values.count(_ == wk)) <= 1 } wk.cancel()
+    withRegistered(registered -- fs)
+  }
+
+  /** Adds all of `fs` to the watched paths. */
+  private[sbt] def ++(fs: Iterable[Path]): WatchState = {
+    val newKeys =
+      fs.filter(Files.exists(_)).foldLeft(registered) {
+        case (ks, d) if Files.isDirectory(d) =>
+          if (registered.contains(d)) ks
+          else ks + (d -> service.register(d, WatchState.events: _*))
+
+        case (ks, f) =>
+          val parent = f.getParent
+          if (registered.contains(parent)) ks + (f -> registered(parent))
+          else ks + (f -> service.register(parent, WatchState.events: _*))
       }
+    withRegistered(newKeys)
+  }
+
+  /** Retrieve events from the `WatchService` */
+  private[sbt] def pollEvents(): Iterable[(Path, WatchEvent[_])] = {
+    val events = service.pollEvents
+    events.toIterable.flatMap {
+      case (k, evs) => evs.map((k.watchable().asInstanceOf[Path], _))
     }
+  }
+
+  /** A new state, with a new `count`. */
+  private[sbt] def withCount(count: Int): WatchState =
+    new WatchState(count, sources, service, registered)
+
+  /** A new state, with new keys registered. */
+  private[sbt] def withRegistered(registered: Map[Path, WatchKey]): WatchState =
+    new WatchState(count, sources, service, registered)
 }
-private[sbt] final class WatchState(val lastCallbackCallTime: Long, val previousFiles: Set[String], val awaitingQuietPeriod: Boolean, val count: Int) {
-  def previousFileCount: Int = previousFiles.size
+
+/**
+ * Represents how to acquire a list of items to watch.
+ * @param base          Where to start looking for files.
+ * @param includeFilter Filter to apply to determine whether to include a file.
+ * @param excludeFilter Filter to apply to determine whether to ignore a file.
+ */
+final class Source(base: File, includeFilter: FileFilter, excludeFilter: FileFilter) {
+  /**
+   * Determine whether `p` should be included in this source.
+   * @param p           The path to test.
+   * @param includeDirs Whether all directories should be included.
+   * @return            True, if `p` should be included, false otherwise.
+   */
+  private[sbt] def accept(p: Path, includeDirs: Boolean = false): Boolean = {
+    val inc =
+      if (includeDirs) DirectoryFilter || includeFilter
+      else includeFilter
+
+    p.startsWith(base.toPath) &&
+      inc.accept(p.toFile) &&
+      !excludeFilter.accept(p.toFile)
+  }
+
+  /**
+   * Gathers all the paths from this source without applying filters.
+   * @return A sequence of all the paths collected from this source.
+   */
+  private[sbt] def getUnfilteredPaths(): Seq[Path] =
+    base.allPaths.get.map(_.toPath)
 }
 
-private[sbt] object WatchState {
-  def empty = new WatchState(0L, Set.empty[String], false, 0)
+object WatchState {
+  /** What events should be monitored */
+  val events: Array[WatchEvent.Kind[Path]] = Array(ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY)
+
+  /**
+   * An empty `WatchState`.
+   * @param service The `WatchService` to use to monitor the file system.
+   * @param sources The sources from where to collect the paths.
+   * @return An initial `WatchState`.
+   */
+  def empty(service: WatchService, sources: Seq[Source]): WatchState = {
+    val initFiles = sources.flatMap(_.getUnfilteredPaths())
+    assert(initFiles.nonEmpty)
+    val initState = new WatchState(0, sources, service, Map.empty) ++ initFiles
+    service.init()
+    initState
+  }
+
 }

io/src/main/scala/sbt/io/PollingWatchService.scala

@@ -0,0 +1,165 @@
+package sbt.io
+
+import java.nio.file.{ClosedWatchServiceException, Files, Path => JPath, Watchable, WatchKey, WatchEvent}
+import java.nio.file.StandardWatchEventKinds._
+import java.util.{List => JList}
+
+import sbt.io.syntax._
+import scala.collection.mutable
+
+/** A `WatchService` that polls the filesystem every `delayMs` milliseconds. */
+class PollingWatchService(delayMs: Long) extends WatchService {
+  private var closed: Boolean       = false
+  private val thread: PollingThread = new PollingThread(delayMs)
+  private val keys: mutable.Map[JPath, PollingWatchKey] = mutable.Map.empty
+  private val pathLengthOrdering: Ordering[JPath] =
+    Ordering.fromLessThan {
+      case (null, _) | (_, null) => true
+      case (a, b) =>
+        a.toString.length < b.toString.length
+    }
+
+  private val watched: mutable.Map[JPath, Seq[WatchEvent.Kind[JPath]]] =
+    mutable.Map.empty
+
+  override def close(): Unit =
+    closed = true
+
+  override def init(): Unit = {
+    ensureNotClosed()
+    thread.start()
+    while (!thread.initDone) {
+      Thread.sleep(100)
+    }
+  }
+
+  override def poll(timeoutMs: Long): WatchKey = thread.keysWithEvents.synchronized {
+    ensureNotClosed()
+    thread.keysWithEvents.headOption.map { k =>
+      thread.keysWithEvents -= k
+      k
+    }.orNull
+  }
+
+  override def pollEvents(): Map[WatchKey, Seq[WatchEvent[JPath]]] = thread.keysWithEvents.synchronized {
+    import scala.collection.JavaConverters._
+    ensureNotClosed()
+    val events = thread.keysWithEvents.map { k =>
+      k -> k.pollEvents().asScala.asInstanceOf[Seq[WatchEvent[JPath]]]
+    }
+    thread.keysWithEvents.clear()
+    events.toMap
+  }
+
+  override def register(path: JPath, events: WatchEvent.Kind[JPath]*): WatchKey = {
+    ensureNotClosed()
+    val key = new PollingWatchKey(thread, path, new java.util.ArrayList[WatchEvent[_]])
+    keys += path -> key
+    watched += path -> events
+    key
+  }
+
+  private def ensureNotClosed(): Unit =
+    if (closed) throw new ClosedWatchServiceException
+
+  private class PollingThread(delayMs: Long) extends Thread {
+    private var fileTimes: Map[JPath, Long] = Map.empty
+    var initDone = false
+    val keysWithEvents = mutable.LinkedHashSet.empty[WatchKey]
+
+    override def run(): Unit =
+      while (!closed) {
+        populateEvents()
+        initDone = true
+        Thread.sleep(delayMs)
+      }
+
+    def getFileTimes(): Map[JPath, Long] = {
+      val results = mutable.Map.empty[JPath, Long]
+      watched.toSeq.sortBy(_._1)(pathLengthOrdering).foreach {
+        case (p, _) =>
+          if (!results.contains(p))
+            p.toFile.allPaths.get.foreach(f => results += f.toPath -> f.lastModified)
+      }
+      results.toMap
+    }
+
+    private def addEvent(path: JPath, ev: WatchEvent[JPath]): Unit = keysWithEvents.synchronized {
+      keys.get(path).foreach { k =>
+        keysWithEvents += k
+        k.events.add(ev)
+      }
+    }
+
+    private def populateEvents(): Unit = {
+      val newFileTimes = getFileTimes()
+      val newFiles     = newFileTimes.keySet
+      val oldFiles     = fileTimes.keySet
+
+      val deletedFiles  = (oldFiles -- newFiles).toSeq
+      val createdFiles  = (newFiles -- oldFiles).toSeq
+
+      val modifiedFiles = fileTimes.collect {
+        case (p, oldTime) if newFileTimes.getOrElse(p, 0L) > oldTime => p
+      }
+      fileTimes = newFileTimes
+
+      deletedFiles.foreach { deleted =>
+        val parent = deleted.getParent
+        if (watched.getOrElse(parent, Seq.empty).contains(ENTRY_DELETE)) {
+          val ev = new PollingWatchEvent(parent.relativize(deleted), ENTRY_DELETE)
+          addEvent(parent, ev)
+        }
+        watched -= deleted
+      }
+
+      createdFiles.sorted(pathLengthOrdering).foreach {
+        case dir if Files.isDirectory(dir) =>
+          val parent = dir.getParent
+          val parentEvents = watched.getOrElse(parent, Seq.empty)
+          if (parentEvents.contains(ENTRY_CREATE)) {
+            val ev = new PollingWatchEvent(parent.relativize(dir), ENTRY_CREATE)
+            addEvent(parent, ev)
+          }
+
+        case file =>
+          val parent = file.getParent
+          if (watched.getOrElse(parent, Seq.empty).contains(ENTRY_CREATE)) {
+            val ev = new PollingWatchEvent(parent.relativize(file), ENTRY_CREATE)
+            addEvent(parent, ev)
+          }
+      }
+
+      modifiedFiles.foreach {
+        case file =>
+          val parent = file.getParent
+          if (watched.getOrElse(parent, Seq.empty).contains(ENTRY_MODIFY)) {
+            val ev = new PollingWatchEvent(parent.relativize(file), ENTRY_MODIFY)
+            addEvent(parent, ev)
+          }
+      }
+    }
+
+  }
+
+  private class PollingWatchKey(origin: PollingThread,
+    override val watchable: Watchable,
+    val events: JList[WatchEvent[_]]) extends WatchKey {
+      override def cancel(): Unit = ()
+      override def isValid(): Boolean = true
+      override def pollEvents(): java.util.List[WatchEvent[_]] = origin.keysWithEvents.synchronized {
+        origin.keysWithEvents -= this
+        val evs = new java.util.ArrayList[WatchEvent[_]](events)
+        events.clear()
+        evs
+      }
+      override def reset(): Boolean = true
+    }
+
+}
+
+private class PollingWatchEvent(override val context: JPath,
+                                override val kind: WatchEvent.Kind[JPath]) extends WatchEvent[JPath] {
+  override val count: Int = 1
+}
+