sbt.internal.inc.caching.ClasspathCache.scala Maven / Gradle / Ivy

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Incremental compiler of Scala
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/*
 * Zinc - The incremental compiler for Scala.
 * Copyright Scala Center, Lightbend, and Mark Harrah
 *
 * Licensed under Apache License 2.0
 * SPDX-License-Identifier: Apache-2.0
 *
 * See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership.
 */

package sbt.internal.inc.caching

import java.nio.file.{ Files, NoSuchFileException, Path }
import java.nio.file.attribute.{ BasicFileAttributes, FileTime }
import java.util.concurrent.ConcurrentHashMap

import xsbti.compile.FileHash
import sbt.internal.inc.Stamper
import sbt.io.IO
import scala.util.control.NonFatal

object ClasspathCache {
  // copied from io
  private val jdkTimestamps = {
    System.getProperty("sbt.io.jdktimestamps") match {
      case null =>
        System.getProperty("java.specification.version") match {
          case null => false
          case sv =>
            try {
              sv.split("\\.").last.toInt >= 10
            } catch { case NonFatal(_) => false }
        }
      case p => p.toLowerCase != "false"
    }
  }
  // For more safety, store both the time and size
  private type JarMetadata = (FileTime, Long)
  private[this] val cacheMetadataJar = new ConcurrentHashMap[Path, (JarMetadata, FileHash)]()
  private def emptyFileHash(file: Path) = FileHash.of(file, 42)
  private def genFileHash(file: Path, metadata: JarMetadata): FileHash = {
    val newHash = FileHash.of(file, Stamper.forFarmHashP(file).getValueId())
    cacheMetadataJar.put(file, (metadata, newHash))
    newHash
  }

  def hashClasspath(classpath: Seq[Path]): Array[FileHash] = {
    // #433: Cache jars with their metadata to avoid recomputing hashes transitively in other projects
    def fromCacheOrHash(file: Path): FileHash = {
      try {
        // `readAttributes` needs to be guarded by `file.exists()`, otherwise it fails
        val attrs = Files.readAttributes(file, classOf[BasicFileAttributes])
        if (attrs.isDirectory) emptyFileHash(file)
        else {
          val lastModified =
            if (jdkTimestamps) attrs.lastModifiedTime()
            else FileTime.fromMillis(IO.getModifiedTimeOrZero(file.toFile))
          val currentMetadata =
            (lastModified, attrs.size())
          Option(cacheMetadataJar.get(file)) match {
            case Some((metadata, hashHit)) if metadata == currentMetadata => hashHit
            case _ => genFileHash(file, currentMetadata)
          }
        }
      } catch { case _: NoSuchFileException => emptyFileHash(file) }
    }

    import scala.collection.parallel._
    classpath.toParArray.map(fromCacheOrHash).toArray
  }
}