Avoid excessive file stats during classfile writing

The existing implementation pessimistically checks that all parent directories of the about-to-be-written class file are indeed directories. This commit bypasses this logic for the common case of writing to a regular directory on disk, and optimistically assumes that the parent directory exists. If an exception is thrown during writing, it attempts to create the parent directory. This still avoids a compiler crash if a parent directory is actually a file, which is tested by the existing test, `run/t5717.scala`.
scala · retronym · Apr 21, 2017 · Mar 15, 2017 · Mar 15, 2017 · Mar 15, 2017
commit 7a6dc1abbfc9afda27623dd43424c252dcec8088
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
@@ -6,10 +6,15 @@
 package scala.tools.nsc
 package backend.jvm
 
-import java.io.{ DataOutputStream, FileOutputStream, IOException, File => JFile }
+import java.io.{DataOutputStream, FileOutputStream, IOException, File => JFile}
+import java.nio.file.{FileAlreadyExistsException, Files}
+import java.nio.file.attribute.BasicFileAttributes
+
 import scala.tools.nsc.io._
 import java.util.jar.Attributes.Name
+
 import scala.language.postfixOps
+import scala.reflect.io.PlainNioFile
 
 /** Can't output a file due to the state of the file system. */
 class FileConflictException(msg: String, val file: AbstractFile) extends IOException(msg)
@@ -29,13 +34,25 @@ trait BytecodeWriters {
    * @param clsName cls.getName
    */
   def getFile(base: AbstractFile, clsName: String, suffix: String): AbstractFile = {
-    def ensureDirectory(dir: AbstractFile): AbstractFile =
-      if (dir.isDirectory) dir
-      else throw new FileConflictException(s"${base.path}/$clsName$suffix: ${dir.path} is not a directory", dir)
-    var dir = base
-    val pathParts = clsName.split("[./]").toList
-    for (part <- pathParts.init) dir = ensureDirectory(dir) subdirectoryNamed part
-    ensureDirectory(dir) fileNamed pathParts.last + suffix
+    if (base.file != null) {
+      fastGetFile(base, clsName, suffix)
+    } else {
+      def ensureDirectory(dir: AbstractFile): AbstractFile =
+        if (dir.isDirectory) dir
+        else throw new FileConflictException(s"${base.path}/$clsName$suffix: ${dir.path} is not a directory", dir)
+      var dir = base
+      val pathParts = clsName.split("[./]").toList
+      for (part <- pathParts.init) dir = ensureDirectory(dir) subdirectoryNamed part
+      ensureDirectory(dir) fileNamed pathParts.last + suffix
+    }
+  }
+  private def fastGetFile(base: AbstractFile, clsName: String, suffix: String) = {
+    val index = clsName.lastIndexOf('/')
+    val (packageName, simpleName) = if (index > 0) {
+      (clsName.substring(0, index), clsName.substring(index + 1))
+    } else ("", clsName)
+    val directory = base.file.toPath.resolve(packageName)
+    new PlainNioFile(directory.resolve(simpleName + suffix))
   }
   def getFile(sym: Symbol, clsName: String, suffix: String): AbstractFile =
     getFile(outputDirectory(sym), clsName, suffix)
@@ -118,10 +135,20 @@ trait BytecodeWriters {
     def writeClass(label: String, jclassName: String, jclassBytes: Array[Byte], outfile: AbstractFile) {
       assert(outfile != null,
              "Precisely this override requires its invoker to hand out a non-null AbstractFile.")
-      val outstream = new DataOutputStream(outfile.bufferedOutput)
+      if (outfile.file != null) {
+        try {
+          Files.write(outfile.file.toPath, jclassBytes)
+        } catch {
+          case _: java.nio.file.NoSuchFileException =>
+            Files.createDirectories(outfile.file.toPath.getParent)
+            Files.write(outfile.file.toPath, jclassBytes)
+        }
+      } else {
+        val outstream = new DataOutputStream(outfile.bufferedOutput)
+        try outstream.write(jclassBytes, 0, jclassBytes.length)
+        finally outstream.close()
+      }
 
-      try outstream.write(jclassBytes, 0, jclassBytes.length)
-      finally outstream.close()
       informProgress("wrote '" + label + "' to " + outfile)
     }
   }

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
@@ -410,6 +410,10 @@ abstract class GenBCode extends BCodeSyncAndTry {
           catch {
             case e: FileConflictException =>
               error(s"error writing $jclassName: ${e.getMessage}")
+            case e: java.nio.file.FileSystemException =>
+              if (settings.debug)
+                e.printStackTrace()
+              error(s"error writing $jclassName: ${e.getClass.getName} ${e.getMessage}")
           }
         }
       }