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Merge pull request #495 from lrytz/toConserve
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preserve immutable collections in to(Target) conversions
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@lrytz
lrytz authored Nov 8, 2021
2 parents fc741eb + 2133b3f commit d55a12f
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Showing 4 changed files with 322 additions and 67 deletions.
79 changes: 44 additions & 35 deletions build.sbt
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Original file line number Diff line number Diff line change
Expand Up @@ -72,44 +72,53 @@ lazy val compat = new MultiScalaCrossProject(
sharedSourceDir / "scala-2.11_2.12"
}
},
Test / unmanagedSourceDirectories += {
val sharedSourceDir = (ThisBuild / baseDirectory).value / "compat/src/test"
CrossVersion.partialVersion(scalaVersion.value) match {
case Some((3, _) | (2, 13)) =>
sharedSourceDir / "scala-2.13"
case _ =>
sharedSourceDir / "scala-2.11_2.12"
}
},
versionPolicyIntention := Compatibility.BinaryCompatible,
)
.jvmSettings(
Test / unmanagedSourceDirectories += (ThisBuild / baseDirectory).value / "compat/src/test/scala-jvm",
junit,
mimaBinaryIssueFilters ++= {
import com.typesafe.tools.mima.core._
import com.typesafe.tools.mima.core.ProblemFilters._
Seq(
exclude[ReversedMissingMethodProblem]("scala.collection.compat.PackageShared.*"), // it's package-private
exclude[Problem]("scala.collection.compat.*PreservingBuilder*")
)
},
)
.jvmSettings(
Test / unmanagedSourceDirectories += (ThisBuild / baseDirectory).value / "compat/src/test/scala-jvm",
junit,
)
.disablePlugins(ScalafixPlugin),
_.jsSettings(
scalacOptions ++= {
val x = (LocalRootProject / baseDirectory).value.toURI.toString
val y = "https://raw.githubusercontent.com/scala/scala-collection-compat/" + sys.process
.Process("git rev-parse HEAD")
.lineStream_!
.head
val opt = CrossVersion.partialVersion(scalaVersion.value) match {
case Some((3, _)) => "-scalajs-mapSourceURI"
case _ => "-P:scalajs:mapSourceURI"
}
Seq(s"$opt:$x->$y/")
},
Test / fork := false // Scala.js cannot run forked tests
)
.jsEnablePlugins(ScalaJSJUnitPlugin),
scalacOptions ++= {
val x = (LocalRootProject / baseDirectory).value.toURI.toString
val y = "https://raw.githubusercontent.com/scala/scala-collection-compat/" + sys.process
.Process("git rev-parse HEAD")
.lineStream_!
.head
val opt = CrossVersion.partialVersion(scalaVersion.value) match {
case Some((3, _)) => "-scalajs-mapSourceURI"
case _ => "-P:scalajs:mapSourceURI"
}
Seq(s"$opt:$x->$y/")
},
Test / fork := false // Scala.js cannot run forked tests
).jsEnablePlugins(ScalaJSJUnitPlugin),
_.nativeSettings(
nativeLinkStubs := true,
addCompilerPlugin(
"org.scala-native" % "junit-plugin" % nativeVersion cross CrossVersion.full
),
libraryDependencies += "org.scala-native" %%% "junit-runtime" % nativeVersion,
Test / fork := false // Scala Native cannot run forked tests
)
nativeLinkStubs := true,
addCompilerPlugin(
"org.scala-native" % "junit-plugin" % nativeVersion cross CrossVersion.full
),
libraryDependencies += "org.scala-native" %%% "junit-runtime" % nativeVersion,
Test / fork := false // Scala Native cannot run forked tests
)
)

val compat211 = compat(Seq(JSPlatform, JVMPlatform, NativePlatform), scala211)
Expand Down Expand Up @@ -171,7 +180,7 @@ lazy val scalafixRules = project
.settings(
scalaModuleAutomaticModuleName := None,
versionPolicyIntention := Compatibility.None,
versionCheck := {}, // I don't understand why this fails otherwise?! oh well
versionCheck := {}, // I don't understand why this fails otherwise?! oh well
name := "scala-collection-migrations",
scalaVersion := scalafixScala212,
libraryDependencies += "ch.epfl.scala" %% "scalafix-core" % scalafixVersion
Expand Down Expand Up @@ -289,14 +298,14 @@ lazy val scalafixTests = project
.dependsOn(scalafixInput, scalafixRules)
.enablePlugins(BuildInfoPlugin, ScalafixTestkitPlugin)

val ciScalaVersion = sys.env.get("CI_SCALA_VERSION").flatMap(Version.parse)
val isScalaJs = sys.env.get("CI_PLATFORM") == Some("js")
val isScalaNative = sys.env.get("CI_PLATFORM") == Some("native")
val isScalafix = sys.env.get("CI_MODE") == Some("testScalafix")
val isScalafmt = sys.env.get("CI_MODE") == Some("testScalafmt")
val isBinaryCompat = sys.env.get("CI_MODE") == Some("testBinaryCompat")
val isHeaderCheck = sys.env.get("CI_MODE") == Some("headerCheck")
val jdkVersion = sys.env.get("CI_JDK").map(_.toInt)
val ciScalaVersion = sys.env.get("CI_SCALA_VERSION").flatMap(Version.parse)
val isScalaJs = sys.env.get("CI_PLATFORM") == Some("js")
val isScalaNative = sys.env.get("CI_PLATFORM") == Some("native")
val isScalafix = sys.env.get("CI_MODE") == Some("testScalafix")
val isScalafmt = sys.env.get("CI_MODE") == Some("testScalafmt")
val isBinaryCompat = sys.env.get("CI_MODE") == Some("testBinaryCompat")
val isHeaderCheck = sys.env.get("CI_MODE") == Some("headerCheck")
val jdkVersion = sys.env.get("CI_JDK").map(_.toInt)

// required by sbt-scala-module
inThisBuild {
Expand Down
53 changes: 34 additions & 19 deletions compat/src/main/scala-2.11_2.12/scala/collection/compat/CompatImpl.scala
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,37 +14,35 @@ package scala.collection.compat

import scala.reflect.ClassTag
import scala.collection.generic.CanBuildFrom
import scala.{collection => c}
import scala.collection.{immutable => i, mutable => m}

/* builder optimized for a single ++= call, which returns identity on result if possible
* and defers to the underlying builder if not.
*/
private final class IdentityPreservingBuilder[A, CC[X] <: TraversableOnce[X]](
that: m.Builder[A, CC[A]])(implicit ct: ClassTag[CC[A]])
extends m.Builder[A, CC[A]] {
private abstract class PreservingBuilder[A, C <: TraversableOnce[A]] extends m.Builder[A, C] {
val that: m.Builder[A, C]
val ct: ClassTag[C]

//invariant: ruined => (collection == null)
var collection: CC[A] = null.asInstanceOf[CC[A]]
var ruined = false
var collection: C = null.asInstanceOf[C]
var ruined = false

private[this] def ruin(): Unit = {
if (collection != null) that ++= collection
collection = null.asInstanceOf[CC[A]]
collection = null.asInstanceOf[C]
ruined = true
}

override def ++=(elems: TraversableOnce[A]): this.type =
elems match {
case ct(ca) if collection == null && !ruined => {
collection = ca
this
}
case _ => {
override def ++=(elems: TraversableOnce[A]): this.type = {
(if (collection == null && !ruined) ct.unapply(elems) else None) match {
case Some(c) => collection = c
case _ =>
ruin()
that ++= elems
this
}
}
this
}

def +=(elem: A): this.type = {
ruin()
Expand All @@ -53,14 +51,31 @@ private final class IdentityPreservingBuilder[A, CC[X] <: TraversableOnce[X]](
}

def clear(): Unit = {
collection = null.asInstanceOf[CC[A]]
if (ruined) that.clear()
ruined = false
collection = null.asInstanceOf[C]
if (ruined) {
that.clear()
ruined = false
}
}

def result(): CC[A] = if (collection == null) that.result() else collection
def result(): C = if (collection == null) that.result() else collection
}

private final class IdentityPreservingBuilder[A, CC[X] <: TraversableOnce[X]](
val that: m.Builder[A, CC[A]])(implicit val ct: ClassTag[CC[A]])
extends PreservingBuilder[A, CC[A]]

private final class IdentityPreservingBitSetBuilder[C <: c.BitSet](val that: m.Builder[Int, C])(
implicit val ct: ClassTag[C])
extends PreservingBuilder[Int, C]

private final class IdentityPreservingMapBuilder[
K,
V,
CC[X, Y] <: c.Map[X, Y] with c.MapLike[X, Y, CC[X, Y]]](val that: m.Builder[(K, V), CC[K, V]])(
implicit val ct: ClassTag[CC[K, V]])
extends PreservingBuilder[(K, V), CC[K, V]]

private[compat] object CompatImpl {
def simpleCBF[A, C](f: => m.Builder[A, C]): CanBuildFrom[Any, A, C] =
new CanBuildFrom[Any, A, C] {
Expand Down
116 changes: 103 additions & 13 deletions compat/src/main/scala-2.11_2.12/scala/collection/compat/PackageShared.scala
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,10 @@

package scala.collection.compat

import scala.annotation.nowarn
import scala.collection.generic._
import scala.reflect.ClassTag
import scala.collection.{
BitSet,
GenTraversable,
IterableLike,
IterableView,
Expand Down Expand Up @@ -61,39 +61,129 @@ private[compat] trait PackageShared {
must be non-strict
*/
def builder: m.Builder[A, CC[A]] = fact match {
case c.Seq | i.Seq => new IdentityPreservingBuilder[A, i.Seq](i.Seq.newBuilder[A])
case c.Seq | i.Seq =>
new IdentityPreservingBuilder[A, i.Seq](i.Seq.newBuilder[A])

case c.LinearSeq | i.LinearSeq =>
new IdentityPreservingBuilder[A, i.LinearSeq](i.LinearSeq.newBuilder[A])
case i.Queue =>
new IdentityPreservingBuilder[A, i.Queue](i.Queue.newBuilder[A])
case i.Stream =>
new IdentityPreservingBuilder[A, i.Stream](i.Stream.newBuilder[A])
case i.Stack =>
new IdentityPreservingBuilder[A, i.Stack](i.Stack.newBuilder[A]): @nowarn("cat=deprecation")
case i.List =>
new IdentityPreservingBuilder[A, i.List](i.List.newBuilder[A])

case c.IndexedSeq | i.IndexedSeq =>
new IdentityPreservingBuilder[A, i.IndexedSeq](i.IndexedSeq.newBuilder[A])
case i.Vector =>
new IdentityPreservingBuilder[A, i.Vector](i.Vector.newBuilder[A])

case c.Set | i.Set =>
new IdentityPreservingBuilder[A, i.Set](i.Set.newBuilder[A])

case i.HashSet =>
new IdentityPreservingBuilder[A, i.HashSet](i.HashSet.newBuilder[A])
case i.ListSet =>
new IdentityPreservingBuilder[A, i.ListSet](i.ListSet.newBuilder[A])

case c.Iterable | i.Iterable =>
new IdentityPreservingBuilder[A, i.Iterable](i.Iterable.newBuilder[A])

case c.Traversable | i.Traversable =>
new IdentityPreservingBuilder[A, i.Traversable](i.Traversable.newBuilder[A])

case _ => fact.newBuilder[A]
}
simpleCBF(builder)
}

implicit def sortedSetCompanionToCBF[A: Ordering,
CC[X] <: c.SortedSet[X] with c.SortedSetLike[X, CC[X]]](
fact: SortedSetFactory[CC]): CanBuildFrom[Any, A, CC[A]] =
simpleCBF(fact.newBuilder[A])
fact: SortedSetFactory[CC]): CanBuildFrom[Any, A, CC[A]] = {
def builder: m.Builder[A, CC[A]] = {
val b = fact match {
case c.SortedSet | i.SortedSet =>
new IdentityPreservingBuilder[A, i.SortedSet](i.SortedSet.newBuilder[A])
case i.TreeSet =>
new IdentityPreservingBuilder[A, i.TreeSet](i.TreeSet.newBuilder[A])
case _ =>
fact.newBuilder[A]
}
// Cast needed because GADT inference doesn't unify CC (didn't dig down why). Example:
// def t: CC[A] = fact match { case i.SortedSet => null: i.SortedSet[A] }
b.asInstanceOf[m.Builder[A, CC[A]]]
}
simpleCBF(builder)
}

implicit def arrayCompanionToCBF[A: ClassTag](fact: Array.type): CanBuildFrom[Any, A, Array[A]] =
simpleCBF(Array.newBuilder[A])

implicit def mapFactoryToCBF[K, V, CC[A, B] <: Map[A, B] with MapLike[A, B, CC[A, B]]](
fact: MapFactory[CC]): CanBuildFrom[Any, (K, V), CC[K, V]] =
simpleCBF(fact.newBuilder[K, V])
// bounds should be `c.` but binary compatibility
implicit def mapFactoryToCBF[K,
V,
CC[A, B] <: /*c.*/ Map[A, B] with /*c.*/ MapLike[A, B, CC[A, B]]](
fact: MapFactory[CC]): CanBuildFrom[Any, (K, V), CC[K, V]] = {
def builder: m.Builder[(K, V), CC[K, V]] = {
val b = fact match {
case c.Map | i.Map =>
new IdentityPreservingMapBuilder[K, V, i.Map](i.Map.newBuilder[K, V])
case i.HashMap =>
new IdentityPreservingMapBuilder[K, V, i.HashMap](i.HashMap.newBuilder[K, V])
case i.ListMap =>
new IdentityPreservingMapBuilder[K, V, i.ListMap](i.ListMap.newBuilder[K, V])
case _ =>
fact.newBuilder[K, V]
}
// Cast needed because GADT inference doesn't unify CC (didn't dig down why). Example:
// def t: CC[K, V] = fact match { case i.Map => null: i.Map[K, V] }
b.asInstanceOf[m.Builder[(K, V), CC[K, V]]]
}
simpleCBF(builder)
}

implicit def sortedMapFactoryToCBF[
K: Ordering,
V,
CC[A, B] <: c.SortedMap[A, B] with c.SortedMapLike[A, B, CC[A, B]]](
fact: SortedMapFactory[CC]): CanBuildFrom[Any, (K, V), CC[K, V]] =
simpleCBF(fact.newBuilder[K, V])
fact: SortedMapFactory[CC]): CanBuildFrom[Any, (K, V), CC[K, V]] = {
def builder: m.Builder[(K, V), CC[K, V]] = {
val b = fact match {
case c.SortedMap | i.SortedMap =>
new IdentityPreservingMapBuilder[K, V, i.SortedMap](i.SortedMap.newBuilder[K, V])
case i.TreeMap =>
new IdentityPreservingMapBuilder[K, V, i.TreeMap](i.TreeMap.newBuilder[K, V])
case _ =>
fact.newBuilder[K, V]
}
b.asInstanceOf[m.Builder[(K, V), CC[K, V]]]
}
simpleCBF(builder)
}

implicit def bitSetFactoryToCBF(fact: BitSetFactory[BitSet]): CanBuildFrom[Any, Int, BitSet] =
simpleCBF(fact.newBuilder)
implicit def bitSetFactoryToCBF(
fact: BitSetFactory[c.BitSet]): CanBuildFrom[Any, Int, c.BitSet] = {
def builder: m.Builder[Int, c.BitSet] = fact match {
case c.BitSet =>
new IdentityPreservingBitSetBuilder[i.BitSet](i.BitSet.newBuilder)
case _ =>
fact.newBuilder
}
simpleCBF(builder)
}

implicit def immutableBitSetFactoryToCBF(
fact: BitSetFactory[i.BitSet]): CanBuildFrom[Any, Int, ImmutableBitSetCC[Int]] =
simpleCBF(fact.newBuilder)
fact: BitSetFactory[i.BitSet]): CanBuildFrom[Any, Int, ImmutableBitSetCC[Int]] = {
def builder: m.Builder[Int, i.BitSet] = fact match {
case i.BitSet =>
new IdentityPreservingBitSetBuilder[i.BitSet](i.BitSet.newBuilder)
case _ =>
fact.newBuilder
}
simpleCBF(builder)
}

implicit def mutableBitSetFactoryToCBF(
fact: BitSetFactory[m.BitSet]): CanBuildFrom[Any, Int, MutableBitSetCC[Int]] =
Expand Down
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