improvement: Add fallback to 2.3.0 for older Scala versions

src/main/scala/scoverage/ScoverageSbtPlugin.scala

@@ -70,7 +70,18 @@ object ScoverageSbtPlugin extends AutoPlugin {
     coverageReport := coverageReport0.value,
     coverageAggregate := coverageAggregate0.value,
     coverageAggregate / aggregate := false,
-    coverageDataDir := crossTarget.value
+    coverageDataDir := crossTarget.value,
+    coverageScalacPluginVersion := {
+      scalaVersion.value match {
+        case "2.13.11" => "2.3.0"
+        case "2.13.12" => "2.3.0"
+        case "2.13.13" => "2.3.0"
+        case "2.13.14" => "2.3.0"
+        case "2.13.15" => "2.3.0"
+        case "2.12.16" => "2.3.0"
+        case _         => defaultScoverageVersion
+      }
+    }
   ) ++ coverageSettings ++ scalacSettings
 
   private def isScala2(scalaVersion: String) =

src/sbt-test/scoverage/good-coverage-older/build.sbt

@@ -0,0 +1,17 @@
+version := "0.1"
+
+// Set older version to make sure fallbacks work correctly
+scalaVersion := "2.13.11"
+
+libraryDependencies += "org.scalameta" %% "munit" % "1.0.0-M10" % Test
+
+coverageMinimumStmtTotal := 100
+coverageMinimumBranchTotal := 100
+coverageMinimumStmtPerPackage := 100
+coverageMinimumBranchPerPackage := 100
+coverageMinimumStmtPerFile := 100
+coverageMinimumBranchPerFile := 100
+
+coverageFailOnMinimum := true
+
+allowUnsafeScalaLibUpgrade := true

src/sbt-test/scoverage/good-coverage-older/project/plugins.sbt

@@ -0,0 +1,9 @@
+val pluginVersion = sys.props.getOrElse(
+  "plugin.version",
+  throw new RuntimeException(
+    """|The system property 'plugin.version' is not defined.
+       |Specify this property using the scriptedLaunchOpts -D.""".stripMargin
+  )
+)
+
+addSbtPlugin("org.scoverage" % "sbt-scoverage" % pluginVersion)

src/sbt-test/scoverage/good-coverage-older/src/main/scala/GoodCoverage.scala

@@ -0,0 +1,7 @@
+object GoodCoverage {
+
+  def sum(num1: Int, num2: Int) = {
+    if (0 == num1) num2 else if (0 == num2) num1 else num1 + num2
+  }
+
+}

src/sbt-test/scoverage/good-coverage-older/src/main/scala/two/GoodCoverage.scala

@@ -0,0 +1,9 @@
+package two
+
+object GoodCoverage {
+
+  def sum(num1: Int, num2: Int) = {
+    if (0 == num1) num2 else if (0 == num2) num1 else num1 + num2
+  }
+
+}

src/sbt-test/scoverage/good-coverage-older/src/test/scala/GoodCoverageSpec.scala

@@ -0,0 +1,19 @@
+import munit.FunSuite
+
+/** Created by tbarke001c on 7/8/14.
+  */
+class GoodCoverageSpec extends FunSuite {
+
+  test("GoodCoverage should sum two numbers") {
+    assertEquals(GoodCoverage.sum(1, 2), 3)
+    assertEquals(GoodCoverage.sum(0, 3), 3)
+    assertEquals(GoodCoverage.sum(3, 0), 3)
+  }
+
+  test("two.GoodCoverage should sum two numbers") {
+    assertEquals(two.GoodCoverage.sum(1, 2), 3)
+    assertEquals(two.GoodCoverage.sum(0, 3), 3)
+    assertEquals(two.GoodCoverage.sum(3, 0), 3)
+  }
+
+}

src/sbt-test/scoverage/good-coverage-older/test

@@ -0,0 +1,5 @@
+# run scoverage
+> clean
+> coverage
+> test
+> coverageReport