Initial version of parallel collections from the Scala standard library

Moved over from scala/scala @ 36d6e48da258648413e50e5a9d46c94cfc062634
with the necessary adaptations to make it work as a separate module
on top of scala/scala#5603.

- Since the sequential collections cannot implement `Parallelizable`
  anymore, all conversions have to be performed via extension methods
  provided by `scala.collection.parallel.CollectionConverters._`

- `ParIterableLike.sequentially` was changed to use a `newCombiner`
  for building the parallel version from the temporary sequential
  collection.

- `Combiner` has a new convenience method `fromSequential`. `par`
  in `Parallelizable` is now implemented on top of this.

- All parallel collections tests are now in two subprojects, for JUnit
  and ScalaCheck tests respectively. The main codebase is moved to the
  `core` subproject. We are currently using a ScalaCheck build for 2.12
  but it will become incompatible once we start getting serious with the
  new collections library, so this is not a long-term solution. We may
  have to insource ScalaCheck into this project as well, just as we did
  for scala/scala. At least the separation of ScalaCheck and JUnit tests
  will make it easy to temporarily disable the ScalaCheck tests if no
  compatible ScalaCheck build is available.

- Running on the old Travis infrastructure to avoid test failures
  (see travis-ci/travis-ci#3775)

- The build-related parts were copied from
  https://github.com/scala/scala-swing.

Author: szeiger

.gitignore

@@ -0,0 +1,26 @@
+#
+# Are you tempted to edit this file?
+#
+# First consider if the changes make sense for all,
+# or if they are specific to your workflow/system.
+# If it is the latter, you can augment this list with
+# entries in .git/info/excludes
+#
+
+*.jar
+*~
+
+# eclipse, intellij
+/.classpath
+/.project
+/.cache
+/.idea
+/.settings
+
+# bak files produced by ./cleanup-commit
+*.bak
+
+# Mac specific, but that is common enough a dev platform to warrant inclusion.
+.DS_Store
+
+target/

.travis.yml

@@ -0,0 +1,11 @@
+language: scala
+
+sudo: required
+
+env:
+  global:
+    - PUBLISH_JDK=oraclejdk8
+
+script: admin/build.sh
+
+jdk: oraclejdk8

LICENSE

@@ -0,0 +1,28 @@
+Copyright (c) 2002-2016 EPFL
+Copyright (c) 2011-2016 Lightbend, Inc.
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright notice,
+    this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above copyright notice,
+    this list of conditions and the following disclaimer in the documentation
+    and/or other materials provided with the distribution.
+  * Neither the name of the EPFL nor the names of its contributors
+    may be used to endorse or promote products derived from this software
+    without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

@@ -0,0 +1,4 @@
+# Scala Parallel Collections
+
+This Scala standard library module contains the package `scala.collection.parallel` with all parallel collections that
+used to be part of `scala-library` before Scala 2.13.

admin/README.md

@@ -0,0 +1,61 @@
+## Tag Driven Releasing
+
+Copied from https://github.com/scala/scala-java8-compat/commit/4a6cfc97cd95227b86650410e1b632e5ff79335b.
+
+### Background Reading
+
+  - http://docs.travis-ci.com/user/environment-variables/
+  - http://docs.travis-ci.com/user/encryption-keys/
+  - http://docs.travis-ci.com/user/encrypting-files/
+
+### Initial setup for the repository
+
+To configure tag driven releases from Travis CI.
+
+  1. Generate a key pair for this repository with `./admin/genKeyPair.sh`.
+     Edit `.travis.yml` and `admin/build.sh` as prompted.
+  2. Publish the public key to https://pgp.mit.edu
+  3. Store other secrets as encrypted environment variables with `admin/encryptEnvVars.sh`.
+     Edit `.travis.yml` as prompted.
+  4. Edit `.travis.yml` to use `./admin/build.sh` as the build script,
+     and edit that script to use the tasks required for this project.
+  5. Edit `.travis.yml` to select which JDK will be used for publishing.
+
+It is important to add comments in .travis.yml to identify the name
+of each environment variable encoded in a `:secure` section.
+
+After all of these steps, your .travis.yml should contain config of the
+form:
+
+	language: scala
+	env:
+	  global:
+	    - PUBLISH_JDK=openjdk6
+	    # PGP_PASSPHRASE
+	    - secure: "XXXXXX"
+	    # SONA_USER
+	    - secure: "XXXXXX"
+	    # SONA_PASS
+	    - secure: "XXXXXX"
+	script: admin/build.sh
+
+If Sonatype credentials change in the future, step 3 can be repeated
+without generating a new key.
+
+Be sure to use SBT 0.13.7 or higher to avoid [#1430](https://github.com/sbt/sbt/issues/1430)!
+
+### Testing
+
+  1. Follow the release process below to create a dummy release (e.g. 0.1.0-TEST1).
+     Confirm that the release was staged to Sonatype but do not release it to Maven
+     central. Instead, drop the staging repository.
+
+### Performing a release
+
+  1. Create a GitHub "Release" (with a corresponding tag) via the GitHub
+     web interface.
+  2. Travis CI will schedule a build for this release. Review the build logs.
+  3. Log into https://oss.sonatype.org/ and identify the staging repository.
+  4. Sanity check its contents
+  5. Release staging repository to Maven and send out release announcement.
+

admin/build.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+set -e
+
+# prep environment for publish to sonatype staging if the HEAD commit is tagged
+
+# git on travis does not fetch tags, but we have TRAVIS_TAG
+# headTag=$(git describe --exact-match ||:)
+
+if [ "$TRAVIS_JDK_VERSION" == "$PUBLISH_JDK" ] && [[ "$TRAVIS_TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(-[A-Za-z0-9-]+)? ]]; then
+  echo "Going to release from tag $TRAVIS_TAG!"
+  myVer=$(echo $TRAVIS_TAG | sed -e s/^v//)
+  publishVersion='set every version := "'$myVer'"'
+  extraTarget="+publish-signed"
+  cat admin/gpg.sbt >> project/plugins.sbt
+  cp admin/publish-settings.sbt .
+
+  # Copied from the output of genKeyPair.sh
+  K=$encrypted_e923b9d88d53_key
+  IV=$encrypted_e923b9d88d53_iv
+
+  openssl aes-256-cbc -K $K -iv $IV -in admin/secring.asc.enc -out admin/secring.asc -d
+fi
+
+sbt "$publishVersion" clean update +test +publishLocal $extraTarget

admin/encryptEnvVars.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+#
+# Encrypt sonatype credentials so that they can be
+# decrypted in trusted builds on Travis CI.
+#
+set -e
+
+read -s -p 'SONA_USER: ' SONA_USER
+travis encrypt SONA_USER="$SONA_USER"
+read -s -p 'SONA_PASS: ' SONA_PASS
+travis encrypt SONA_PASS="$SONA_PASS"

admin/genKeyPair.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+#
+# Generates a key pair for this repository to sign artifacts.
+# Encrypt the private key and its passphrase in trusted builds
+# on Travis CI.
+#
+set -e
+
+# Based on https://gist.github.com/kzap/5819745:
+function promptDelete() {
+    if [[ -f "$1" ]]; then
+        echo About to delete $1, Enter for okay / CTRL-C to cancel
+        read
+        rm "$1"
+    fi
+}
+for f in admin/secring.asc.enc admin/secring.asc admin/pubring.asc; do promptDelete "$f"; done
+
+echo Generating key pair. Please enter 1. repo name 2. scala-internals@googlegroups.com, 3. a new passphrase
+echo Be careful when using special characters in the passphrase, see http://docs.travis-ci.com/user/encryption-keys/#Note-on-escaping-certain-symbols
+cp admin/gpg.sbt project
+sbt 'set pgpReadOnly := false' \
+    'set pgpPublicRing := file("admin/pubring.asc")' \
+    'set pgpSecretRing := file("admin/secring.asc")' \
+    'pgp-cmd gen-key'
+rm project/gpg.sbt
+
+echo ============================================================================================
+echo Encrypting admin/secring.asc. Update K and IV variables in admin/build.sh accordingly.
+echo ============================================================================================
+travis encrypt-file admin/secring.asc
+rm admin/secring.asc
+mv secring.asc.enc admin
+
+echo ============================================================================================
+echo Encrypting environment variables. Add each to a line in .travis.yml. Include a comment
+echo with the name of the corresponding variable
+echo ============================================================================================
+read -s -p 'PGP_PASSPHRASE: ' PGP_PASSPHRASE
+travis encrypt PGP_PASSPHRASE="$PGP_PASSPHRASE"
+

admin/gpg.sbt

@@ -0,0 +1,2 @@
+
+addSbtPlugin("com.typesafe.sbt" % "sbt-pgp" % "0.8.3") // only added when publishing, see build.sh

admin/publish-settings.sbt

@@ -0,0 +1,9 @@
+def env(key: String) = Option(System.getenv(key)).getOrElse("")
+
+pgpPassphrase := Some(env("PGP_PASSPHRASE").toArray)
+
+pgpPublicRing := file("admin/pubring.asc")
+
+pgpSecretRing := file("admin/secring.asc")
+
+credentials   += Credentials("Sonatype Nexus Repository Manager", "oss.sonatype.org", env("SONA_USER"), env("SONA_PASS"))

build.sbt

@@ -0,0 +1,37 @@
+import com.typesafe.tools.mima.plugin.{MimaPlugin, MimaKeys}
+
+resolvers in ThisBuild += "scala-pr" at "https://scala-ci.typesafe.com/artifactory/scala-pr-validation-snapshots/"
+
+// this is the SHA of https://github.com/scala/scala/pull/5603 as of 2017-01-12
+// (that's the PR that removes the parallel collections)
+crossScalaVersions in ThisBuild := Seq("2.13.0-eb9fdcd-SNAPSHOT")
+
+scalaVersion in ThisBuild       := crossScalaVersions.value.head
+
+version in ThisBuild            := "1.0.0-SNAPSHOT"
+
+scalacOptions in ThisBuild      ++= Seq("-deprecation", "-feature")
+
+cancelable in Global := true
+
+lazy val core = project.in(file("core")).settings(scalaModuleSettings).settings(scalaModuleOsgiSettings).settings(
+  name := "scala-parallel-collections",
+  OsgiKeys.exportPackage := Seq(s"scala.collection.parallel.*;version=${version.value}"),
+  mimaPreviousVersion := None
+)
+
+lazy val junit = project.in(file("junit")).settings(
+  libraryDependencies += "com.novocode" % "junit-interface" % "0.11" % "test",
+  testOptions += Tests.Argument(TestFrameworks.JUnit, "-a", "-v"),
+  fork in Test := true
+).dependsOn(testmacros, core)
+
+lazy val scalacheck = project.in(file("scalacheck")).settings(
+  libraryDependencies += "org.scalacheck" % "scalacheck_2.12" % "1.13.4",
+  fork in Test := true,
+  testOptions in Test += Tests.Argument(TestFrameworks.ScalaCheck, "-workers", "1", "-minSize", "0", "-maxSize", "4000", "-minSuccessfulTests", "5")
+).dependsOn(core)
+
+lazy val testmacros = project.in(file("testmacros")).settings(
+  libraryDependencies += "org.scala-lang" % "scala-compiler" % scalaVersion.value
+)

src/library/scala/collection/CustomParallelizable.scala renamed to core/src/main/scala/scala/collection/CustomParallelizable.scala

@@ -37,11 +37,7 @@ trait Parallelizable[+A, +ParRepr <: Parallel] extends Any {
    *
    *  @return  a parallel implementation of this collection
    */
-  def par: ParRepr = {
-    val cb = parCombiner
-    for (x <- seq) cb += x
-    cb.result()
-  }
+  def par: ParRepr = parCombiner.fromSequential(seq)
 
   /** The default `par` implementation uses the combiner provided by this method
    *  to create a new parallel collection.