replace java streams with generators

Previously, we created a wrapper for file walking and children listing
to automatically close the underlying java stream, but it lacked the
flexibility and ease of use of standard collections.
Now, we use the geny library to close the stream automatically. It also provides a
subset of scala collection methods (forall, map, etc.)

build.sbt

@@ -172,6 +172,11 @@ lazy val interfaces = project
     )
   )
 
+val genyVersion = Def.setting {
+  if (scalaVersion.value.startsWith("2.11")) "0.1.6"
+  else "0.1.8"
+}
+
 lazy val mtags = project
   .settings(
     moduleName := "mtags",
@@ -189,6 +194,7 @@ lazy val mtags = project
       "com.thoughtworks.qdox" % "qdox" % "2.0-M9", // for java mtags
       "org.jsoup" % "jsoup" % "1.11.3", // for extracting HTML from javadocs
       "org.lz4" % "lz4-java" % "1.6.0", // for streaming hashing when indexing classpaths
+      "com.lihaoyi" %% "geny" % genyVersion.value,
       "org.scalameta" % "semanticdb-scalac-core" % V.scalameta cross CrossVersion.full
     ),
     libraryDependencies ++= {

metals/src/main/scala/scala/meta/internal/builds/Digest.scala

@@ -11,7 +11,6 @@ import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.io.AbsolutePath
 import scala.util.control.NonFatal
 import scala.xml.Node
-import scala.meta.internal.mtags.ListFiles
 
 case class Digest(
     md5: String,
@@ -61,11 +60,9 @@ object Digest {
   ): Boolean = {
     if (!path.isDirectory) true
     else {
-      var success = true
-      ListFiles.foreach(path) { file =>
-        success &= digestFile(file, digest)
+      path.list.forall { file =>
+        digestFile(file, digest)
       }
-      success
     }
   }
 
@@ -122,7 +119,7 @@ object Digest {
       chldrenSuccessful.forall(p => p)
     }
     try {
-      val xml = XML.loadFile(file.toNIO.toFile())
+      val xml = XML.loadFile(file.toNIO.toFile)
       digestElement(xml)
       xml.text.split("\\s+").foreach(word => digest.update(word.getBytes))
       true

metals/src/main/scala/scala/meta/internal/builds/GradleDigest.scala

@@ -1,9 +1,8 @@
 package scala.meta.internal.builds
 
-import scala.meta.io.AbsolutePath
-import scala.meta.internal.mtags.WalkFiles
 import java.security.MessageDigest
-import scala.meta.internal.mtags.ListFiles
+import scala.meta.internal.metals.MetalsEnrichments._
+import scala.meta.io.AbsolutePath
 
 object GradleDigest extends Digestable {
   override protected def digestWorkspace(
@@ -23,33 +22,28 @@ object GradleDigest extends Digestable {
   }
 
   def digestBuildSrc(path: AbsolutePath, digest: MessageDigest): Boolean = {
-    WalkFiles.foreach(path) { file =>
+    path.walk.forall { file =>
       Digest.digestFile(file, digest)
     }
-    true
   }
 
   def digestSubProjects(
       workspace: AbsolutePath,
       digest: MessageDigest
   ): Boolean = {
-    val directories = ListFiles(workspace).filter(_.isDirectory)
+    val directories = workspace.list.filter(_.isDirectory).toList
 
     val (subprojects, dirs) = directories.partition { file =>
-      ListFiles
-        .exists(file) { path =>
-          val stringPath = path.toString
-          stringPath.endsWith(".gradle") || stringPath.endsWith("gradle.kts")
-        }
+      file.list.exists { path =>
+        val stringPath = path.toString
+        stringPath.endsWith(".gradle") || stringPath.endsWith("gradle.kts")
+      }
     }
     /*
        If a dir contains a gradle file we need to treat is as a workspace
      */
     val isSuccessful = subprojects.forall { file =>
-      digestWorkspace(
-        file,
-        digest
-      )
+      digestWorkspace(file, digest)
     }
 
     /*

metals/src/main/scala/scala/meta/internal/builds/MavenDigest.scala

@@ -2,20 +2,19 @@ package scala.meta.internal.builds
 
 import java.security.MessageDigest
 import scala.meta.io.AbsolutePath
-import scala.meta.internal.mtags.WalkFiles
-import scala.meta.internal.mtags.MtagsEnrichments._
+import scala.meta.internal.metals.MetalsEnrichments._
 
 object MavenDigest extends Digestable {
   override protected def digestWorkspace(
       workspace: AbsolutePath,
       digest: MessageDigest
   ): Boolean = {
     Digest.digestFile(workspace.resolve("pom.xml"), digest)
-    WalkFiles.foreach(workspace) { file =>
-      if (file.filename == "pom.xml") {
+    workspace.walk.forall {
+      case file if file.filename == "pom.xml" =>
         Digest.digestFile(file, digest)
-      }
+      case _ =>
+        true
     }
-    true
   }
 }

metals/src/main/scala/scala/meta/internal/builds/SbtDigest.scala

@@ -5,7 +5,6 @@ import java.security.MessageDigest
 import scala.meta.internal.builds.Digest.digestScala
 import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.io.AbsolutePath
-import scala.meta.internal.mtags.ListFiles
 
 object SbtDigest extends Digestable {
 
@@ -20,14 +19,11 @@ object SbtDigest extends Digestable {
     Digest.digestDirectory(project.resolve("project"), digest)
   }
 
-  def digestSbtFiles(
-      path: AbsolutePath,
-      digest: MessageDigest
-  ): Boolean = {
-    if (!path.isDirectory) {
-      true
+  def digestSbtFiles(path: AbsolutePath, digest: MessageDigest): Boolean = {
+    if (path.isDirectory) {
+      path.list.forall(file => digestSbtFile(digest)(file))
     } else {
-      ListFiles.forall(path)(file => digestSbtFile(digest)(file))
+      true
     }
   }
 

metals/src/main/scala/scala/meta/internal/metals/BspServers.scala

@@ -14,7 +14,6 @@ import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.internal.mtags.MD5
 import scala.meta.io.AbsolutePath
 import scala.util.Try
-import scala.meta.internal.mtags.ListFiles
 
 /**
  * Implements BSP server discovery, named "BSP Connection Protocol" in the spec.
@@ -125,7 +124,7 @@ final class BspServers(
     val buf = List.newBuilder[AbsolutePath]
     def visit(dir: AbsolutePath): Unit =
       if (dir.isDirectory) {
-        ListFiles.foreach(dir) { p =>
+        dir.list.foreach { p =>
           if (p.extension == "json") {
             buf += p
           }

metals/src/main/scala/scala/meta/internal/metals/MetalsEnrichments.scala

@@ -294,21 +294,13 @@ object MetalsEnrichments
       }
     }
 
-    def exists: Boolean = {
-      Files.exists(path.toNIO)
-    }
-
     def touch(): Unit = {
       if (!path.exists) {
-        parent.createDirectories()
+        path.parent.createDirectories()
         Files.createFile(path.toNIO)
       }
     }
 
-    def parent: AbsolutePath = {
-      AbsolutePath(path.toNIO.getParent)
-    }
-
     def createDirectories(): AbsolutePath = {
       AbsolutePath(Files.createDirectories(dealias.toNIO))
     }
@@ -318,10 +310,9 @@ object MetalsEnrichments
     }
 
     def writeText(text: String): Unit = {
-      parent.createDirectories()
+      path.parent.createDirectories()
       Files.write(path.toNIO, text.getBytes(StandardCharsets.UTF_8))
     }
-
   }
 
   implicit class XtensionString(value: String) {

metals/src/main/scala/scala/meta/internal/metals/MetalsLanguageServer.scala

@@ -1316,7 +1316,7 @@ class MetalsLanguageServer(
   private def indexWorkspaceSources(): Unit = {
     for {
       (sourceItem, targets) <- buildTargets.sourceItemsToBuildTargets
-      source <- WalkFiles(sourceItem)
+      source <- sourceItem.walk
       if source.isScalaOrJava
     } {
       targets.asScala.foreach { target =>

mtags/src/main/scala/scala/meta/internal/metals/JdkSources.scala

@@ -1,16 +1,16 @@
 package scala.meta.internal.metals
 
-import java.nio.file.Files
-import java.nio.file.Path
 import java.nio.file.Paths
 import scala.meta.io.AbsolutePath
+import scala.meta.io.RelativePath
+import scala.meta.internal.mtags.MtagsEnrichments._
 
 /**
  * Locates zip file on disk that contains the source code for the JDK.
  */
 object JdkSources {
-  private val sources = Paths.get("src.zip")
-  private val libSources = Paths.get("lib").resolve(sources)
+  private val sources = RelativePath(Paths.get("src.zip"))
+  private val libSources = RelativePath(Paths.get("lib")).resolve(sources)
 
   def apply(userJavaHome: Option[String] = None): Option[AbsolutePath] = {
     candidates(userJavaHome).headOption
@@ -23,33 +23,32 @@ object JdkSources {
   }
 
   private def candidates(userJavaHome: Option[String]): List[AbsolutePath] = {
-    def isJdkCandidate(path: Path): Boolean = {
-      def containsJre = Files.exists(path.resolve("jre"))
-      val name = path.getFileName.toString
+    def isJdkCandidate(path: AbsolutePath): Boolean = {
+      def containsJre = path.resolve("jre").exists
+      val name = path.filename.toString
       name.contains("jdk") || containsJre //e.g. jdk-8, java-openjdk-11
     }
 
     for {
       javaHomeString <- userJavaHome.orElse(defaultJavaHome).toList
-      javaHome = Paths.get(javaHomeString)
+      javaHome = AbsolutePath(Paths.get(javaHomeString))
       jdkHome = {
         if (isJdkCandidate(javaHome)) {
           Nil
         } else {
           // In case java.home points to the JRE instead of the JDK,
           // try to find jdk among its siblings
-          Files
-            .list(javaHome.getParent)
+          javaHome.parent.list
             .filter(isJdkCandidate)
-            .toArray[Path](size => new Array(size))
-            .sortBy(_.getFileName)
+            .toArray[AbsolutePath]
+            .sortBy(_.filename)
             .toList
         }
       }
-      jdk <- jdkHome ++ List(javaHome.getParent, javaHome)
+      jdk <- jdkHome ++ List(javaHome.parent, javaHome)
       src <- List(sources, libSources).map(jdk.resolve)
-      if Files.isRegularFile(src)
-    } yield AbsolutePath(src)
+      if src.isFile
+    } yield src
   }
 
   def getOrThrow(): AbsolutePath = {

mtags/src/main/scala/scala/meta/internal/metals/PackageIndex.scala

@@ -20,7 +20,6 @@ import scala.util.control.NonFatal
 import scala.util.Properties
 import java.nio.file.FileSystems
 import java.net.URI
-import scala.meta.internal.mtags.ListFiles
 
 /**
  * An index to lookup classfiles contained in a given classpath.
@@ -137,7 +136,7 @@ class PackageIndex() {
     for {
       pkg <- Files.newDirectoryStream(dir).iterator().asScala
       symbol = pkg.toString.stripPrefix("/packages/").replace('.', '/') + "/"
-      absoluteModuleLink <- ListFiles(AbsolutePath(pkg))
+      absoluteModuleLink <- AbsolutePath(pkg).list
     } {
       val moduleLink = absoluteModuleLink.toNIO
       val module =

mtags/src/main/scala/scala/meta/internal/mtags/MtagsEnrichments.scala

@@ -3,13 +3,15 @@ package scala.meta.internal.mtags
 import com.google.gson.Gson
 import com.google.gson.JsonElement
 import java.nio.charset.StandardCharsets
+import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.Paths
 import java.util
 import java.util.Optional
 import java.util.concurrent.CancellationException
 import java.util.logging.Level
 import java.util.logging.Logger
+import geny.Generator
 import org.eclipse.lsp4j.CompletionItem
 import org.eclipse.lsp4j.MarkupContent
 import org.eclipse.lsp4j.jsonrpc.CancelChecker
@@ -359,4 +361,31 @@ trait MtagsEnrichments {
     def isVar: Boolean = (properties & p.VAR.value) != 0
     def isVal: Boolean = (properties & p.VAL.value) != 0
   }
+
+  implicit class XtensionStream[A](stream: java.util.stream.Stream[A]) {
+    import scala.collection.JavaConverters._
+    def asScala: Generator[A] = {
+      Generator.selfClosing((stream.iterator.asScala, () => stream.close()))
+    }
+  }
+
+  implicit class XtensionAbsolutePath(path: AbsolutePath) {
+    def parent: AbsolutePath = {
+      AbsolutePath(path.toNIO.getParent)
+    }
+
+    def exists: Boolean = {
+      Files.exists(path.toNIO)
+    }
+
+    def walk: Generator[AbsolutePath] = {
+      if (exists) Files.walk(path.toNIO).asScala.map(AbsolutePath(_))
+      else Generator()
+    }
+
+    def list: Generator[AbsolutePath] = {
+      if (exists) Files.walk(path.toNIO).asScala.map(AbsolutePath(_))
+      else Generator()
+    }
+  }
 }