Fix 196

Author: exoego

scalac-scoverage-plugin/src/main/scala/scoverage/plugin.scala

@@ -107,6 +107,14 @@ class ScoverageInstrumentationComponent(val global: Global, extraAfterPhase: Opt
   private var options: ScoverageOptions = new ScoverageOptions()
   private var coverageFilter: CoverageFilter = AllCoverageFilter
 
+  private val isScalaJsEnabled: Boolean = {
+    try {
+      rootMirror.getClassIfDefined("scala.scalajs.js.Any") != NoSymbol
+    } catch {
+      case _: Throwable => false
+    }
+  }
+
   def setOptions(options: ScoverageOptions): Unit = {
     this.options = options
     coverageFilter = new RegexCoverageFilter(options.excludedPackages, options.excludedFiles, options.excludedSymbols)
@@ -215,6 +223,10 @@ class ScoverageInstrumentationComponent(val global: Global, extraAfterPhase: Opt
           if (tree.pos.isDefined && !isStatementIncluded(tree.pos)) {
             coverage.add(statement.copy(ignored = true))
             tree
+          } else if (isUndefinedParameterInScalaJs(tree.symbol)) {
+            coverage.add(statement.copy(ignored = true))
+            statementIds.decrementAndGet()
+            tree
           } else {
             coverage.add(statement)
 
@@ -225,6 +237,11 @@ class ScoverageInstrumentationComponent(val global: Global, extraAfterPhase: Opt
       }
     }
 
+    def isUndefinedParameterInScalaJs(symbol: Symbol): Boolean = {
+      isScalaJsEnabled && symbol != null && symbol.isSynthetic && symbol.isMethod &&
+        symbol.nameString.contains("$default$") &&
+        symbol.tpe.resultType.annotations.exists(_.symbol.nameString == "uncheckedVariance")
+    }
     def isClassIncluded(symbol: Symbol): Boolean = coverageFilter.isClassIncluded(symbol.fullNameString)
     def isFileIncluded(source: SourceFile): Boolean = coverageFilter.isFileIncluded(source)
     def isStatementIncluded(pos: Position): Boolean = coverageFilter.isLineIncluded(pos)

scalac-scoverage-plugin/src/test/scala/scoverage/PluginCoverageScalaJsTest.scala

@@ -0,0 +1,25 @@
+package scoverage
+
+import org.scalatest.{ BeforeAndAfterEachTestData, FunSuite, OneInstancePerTest }
+
+/**
+ * https://github.com/scoverage/scalac-scoverage-plugin/issues/196
+ */
+class PluginCoverageScalaJsTest
+  extends FunSuite
+  with OneInstancePerTest
+  with BeforeAndAfterEachTestData
+  with MacroSupport {
+
+  test("scoverage should ignore default undefined parameter") {
+    val compiler = ScoverageCompiler.default
+    compiler.compileCodeSnippet(
+      """import scala.scalajs.js
+        |
+        |object JSONHelper {
+        |  def toJson(value: String): String = js.JSON.stringify(value)
+        |}""".stripMargin)
+    assert(!compiler.reporter.hasErrors)
+    compiler.assertNMeasuredStatements(4)
+  }
+}

scalac-scoverage-plugin/src/test/scala/scoverage/ScoverageCompiler.scala

@@ -3,6 +3,8 @@ package scoverage
 import java.io.{File, FileNotFoundException}
 import java.net.URL
 
+import scoverage.ScoverageCompiler.getScalaJsJars
+
 import scala.collection.mutable.ListBuffer
 import scala.tools.nsc.{Settings, Global}
 import scala.tools.nsc.plugins.PluginComponent
@@ -17,7 +19,7 @@ object ScoverageCompiler {
     case _                                       => ScalaVersion
   }
 
-  def classPath = getScalaJars.map(_.getAbsolutePath) :+ sbtCompileDir.getAbsolutePath :+ runtimeClasses.getAbsolutePath
+  def classPath = (getScalaJars ++ getScalaJsJars ++ List(sbtCompileDir, runtimeClasses)).map(_.getAbsolutePath)
 
   def settings: Settings = {
     val s = new scala.tools.nsc.Settings
@@ -48,6 +50,11 @@ object ScoverageCompiler {
     scalaJars.map(findScalaJar)
   }
 
+  private def getScalaJsJars: List[File] = {
+    val scalaJars = List("scalajs-library")
+    scalaJars.map(findScalaJsJar)
+  }
+
   private def sbtCompileDir: File = {
     val dir = new File(s"./scalac-scoverage-plugin/target/scala-$ShortScalaVersion/classes")
     if (!dir.exists)
@@ -59,6 +66,8 @@ object ScoverageCompiler {
 
   private def findScalaJar(artifactId: String): File = findIvyJar("org.scala-lang", artifactId, ScalaVersion)
 
+  private def findScalaJsJar(artifactId: String): File = findIvyJar(s"org.scala-js", s"${artifactId}_${ShortScalaVersion}", "0.6.28")
+
   private def findIvyJar(groupId: String, artifactId: String, version: String, packaging: String = "jar"): File = {
     val userHome = System.getProperty("user.home")
     val jarPath = s"$userHome/.ivy2/cache/$groupId/$artifactId/${packaging}s/$artifactId-$version.jar"