compat layer for scala 2.12

Author: yurique

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.13.6, 3.0.0]
+        scala: [2.12.13, 2.13.6, 3.0.0]
         java: [openjdk@1.11.0]
     runs-on: ${{ matrix.os }}
     steps:
@@ -101,6 +101,16 @@ jobs:
             ~/Library/Caches/Coursier/v1
           key: ${{ runner.os }}-sbt-cache-v2-${{ hashFiles('**/*.sbt') }}-${{ hashFiles('project/build.properties') }}
 
+      - name: Download target directories (2.12.13)
+        uses: actions/download-artifact@v2
+        with:
+          name: target-${{ matrix.os }}-2.12.13-${{ matrix.java }}
+
+      - name: Inflate target directories (2.12.13)
+        run: |
+          tar xf targets.tar
+          rm targets.tar
+
       - name: Download target directories (2.13.6)
         uses: actions/download-artifact@v2
         with:

build.sbt

@@ -8,6 +8,7 @@ inThisBuild(
     scalaVersion := ScalaVersions.v213,
     description := "String diff for Scala",
     crossScalaVersions := Seq(
+      ScalaVersions.v212,
       ScalaVersions.v213,
       ScalaVersions.v3
     ),
@@ -22,7 +23,8 @@ inThisBuild(
       "PGP_SECRET"        -> s"$${{ secrets.PGP_SECRET }}",
       "SONATYPE_PASSWORD" -> s"$${{ secrets.SONATYPE_PASSWORD }}",
       "SONATYPE_USERNAME" -> s"$${{ secrets.SONATYPE_USERNAME }}"
-    ))
+    )),
+    versionScheme := Some("early-semver")
   )
 )
 
@@ -39,7 +41,8 @@ lazy val stringdiff =
     .settings(
       ScalaOptions.fixOptions,
       libraryDependencies ++= Seq(
-        "org.scalatest" %%% "scalatest" % "3.2.9" % Test
+        "org.scala-lang.modules" %%% "scala-collection-compat" % "2.4.4",
+        "org.scalatest"          %%% "scalatest"               % "3.2.9" % Test
       )
     )
 

project/ScalaOptions.scala

@@ -12,14 +12,9 @@ object ScalaOptions {
         "-Wunused:params"
       )
     )),
-    scalacOptions ++= (CrossVersion.partialVersion(scalaVersion.value) match {
-      case Some((2, _)) =>
-        Seq(
-          "-Ymacro-annotations"
-        )
-      case Some((3, _)) => Seq()
-      case _            => Seq()
-    }),
+    scalacOptions ++= CrossVersion.partialVersion(scalaVersion.value).collect { case (2, 13) =>
+      "-Ymacro-annotations"
+    },
     (Compile / doc / scalacOptions) ~= (_.filterNot(
       Set(
         "-scalajs",

project/ScalaVersions.scala

@@ -1,4 +1,5 @@
 object ScalaVersions {
+  val v212 = "2.12.13"
   val v213 = "2.13.6"
   val v3   = "3.0.0"
 }

stringdiff/src/main/scala-2.12/app/tulz/diff/compat/IndexedSeqView.scala

@@ -0,0 +1,28 @@
+package app.tulz.diff
+package compat
+
+import scala.collection.SeqView
+import scala.collection.immutable.Range
+
+class IndexedSeqView[A](
+  private[compat] val underlying: SeqView[A, _]
+) {
+  def apply(index: Int): A = underlying(index)
+
+  def size: Int = underlying.length
+
+  def isEmpty: Boolean = underlying.isEmpty
+
+  def concat(other: IndexedSeqView[A]): IndexedSeqView[A] =
+    new IndexedSeqView((underlying ++ other.underlying).view)
+
+  def take(n: Int): IndexedSeqView[A] = new IndexedSeqView(underlying.take(n))
+
+  def slice(from: Int, until: Int): IndexedSeqView[A] = new IndexedSeqView(underlying.slice(from, until))
+
+  def toIndexedSeq: IndexedSeq[A] = underlying.toIndexedSeq
+
+  def indices: Range = underlying.indices
+
+  def forall(predicate: A => Boolean): Boolean = underlying.forall(predicate)
+}

stringdiff/src/main/scala-2.12/app/tulz/diff/compat/IndexedSeqViewOfCharOps.scala

@@ -0,0 +1,9 @@
+package app.tulz.diff.compat
+
+class IndexedSeqViewOfCharOps(
+  underlying: IndexedSeqView[Char]
+) {
+
+  def mkString: String = underlying.underlying.mkString
+
+}

stringdiff/src/main/scala-2.12/app/tulz/diff/compat/IndexedSeqViewOfStringOps.scala

@@ -0,0 +1,9 @@
+package app.tulz.diff.compat
+
+class IndexedSeqViewOfStringOps(
+  underlying: IndexedSeqView[String]
+) {
+
+  def mkString: String = underlying.underlying.mkString
+
+}

stringdiff/src/main/scala-2.12/app/tulz/diff/compat/package.scala

@@ -0,0 +1,24 @@
+package app.tulz.diff
+
+import scala.collection.SeqView
+import scala.language.implicitConversions
+
+package object compat {
+
+  implicit def indexedSeq_ViewToIndexedSeqView[A](
+    underlying: SeqView[A, IndexedSeq[A]]
+  ): IndexedSeqView[A] = new IndexedSeqView[A](underlying)
+
+  implicit def string_ViewToIndexedSeqView(
+    underlying: SeqView[Char, String]
+  ): IndexedSeqView[Char] = new IndexedSeqView[Char](underlying)
+
+  implicit def indexedSeqViewOfCharOps(
+    underlying: IndexedSeqView[Char]
+  ): IndexedSeqViewOfCharOps = new IndexedSeqViewOfCharOps(underlying)
+
+  implicit def indexedSeqViewOfStringOps(
+    underlying: IndexedSeqView[String]
+  ): IndexedSeqViewOfStringOps = new IndexedSeqViewOfStringOps(underlying)
+
+}

stringdiff/src/main/scala-2.13/app/tulz/diff/compat/package.scala

@@ -0,0 +1,7 @@
+package app.tulz.diff
+
+package object compat {
+
+  type IndexedSeqView[+A] = scala.collection.IndexedSeqView[A]
+
+}

stringdiff/src/main/scala-3/app/tulz/diff/compat/package.scala

@@ -0,0 +1,7 @@
+package app.tulz.diff
+
+package object compat {
+
+  type IndexedSeqView[+A] = scala.collection.IndexedSeqView[A]
+
+}