fix: ensure passed in encoding is being used and make some things private

plugin/src/test/scala/scoverage/LocationCompiler.scala

@@ -9,7 +9,7 @@ import scala.tools.nsc.transform.TypingTransformers
 
 import scoverage.reporter.IOUtils
 
-class LocationCompiler(
+private[scoverage] class LocationCompiler(
     settings: scala.tools.nsc.Settings,
     reporter: scala.tools.nsc.reporters.Reporter
 ) extends scala.tools.nsc.Global(settings, reporter) {
@@ -26,7 +26,7 @@ class LocationCompiler(
 
   def writeCodeSnippetToTempFile(code: String): File = {
     val file = File.createTempFile("code_snippet", ".scala")
-    IOUtils.writeToFile(file, code)
+    IOUtils.writeToFile(file, code, None)
     file.deleteOnExit()
     file
   }

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

@@ -13,7 +13,7 @@ import scala.tools.nsc.transform.TypingTransformers
 
 import scoverage.reporter.IOUtils
 
-object ScoverageCompiler {
+private[scoverage] object ScoverageCompiler {
 
   val ScalaVersion: String = scala.util.Properties.versionNumberString
   val ShortScalaVersion: String = (ScalaVersion split "[.]").toList match {
@@ -142,7 +142,7 @@ class ScoverageCompiler(
 
   def writeCodeSnippetToTempFile(code: String): File = {
     val file = File.createTempFile("scoverage_snippet", ".scala")
-    IOUtils.writeToFile(file, code)
+    IOUtils.writeToFile(file, code, None)
     file.deleteOnExit()
     file
   }

reporter/src/main/scala/scoverage/reporter/CoberturaXmlWriter.scala

@@ -27,7 +27,8 @@ class CoberturaXmlWriter(
     IOUtils.writeToFile(
       file,
       "<?xml version=\"1.0\"?>\n<!DOCTYPE coverage SYSTEM \"http://cobertura.sourceforge.net/xml/coverage-04.dtd\">\n" +
-        new PrettyPrinter(120, 4).format(xml(coverage))
+        new PrettyPrinter(120, 4).format(xml(coverage)),
+      sourceEncoding
     )
   }
 

reporter/src/main/scala/scoverage/reporter/IOUtils.scala

@@ -42,12 +42,12 @@ object IOUtils {
   def writeToFile(
       file: File,
       str: String,
-      encoding: String = Codec.UTF8.name
+      encoding: Option[String]
   ) = {
     val writer = new BufferedWriter(
       new OutputStreamWriter(
         new FileOutputStream(file),
-        encoding
+        encoding.getOrElse(Codec.UTF8.name)
       )
     )
     try {

reporter/src/main/scala/scoverage/reporter/ScoverageHtmlWriter.scala

@@ -53,10 +53,18 @@ class ScoverageHtmlWriter(
       try IOUtils.readStreamAsString(in)
       finally in.close()
     }
-    IOUtils.writeToFile(indexFile, index)
-    IOUtils.writeToFile(cssFile, css)
-    IOUtils.writeToFile(packageFile, packageList(coverage).toString())
-    IOUtils.writeToFile(overviewFile, overview(coverage).toString())
+    IOUtils.writeToFile(indexFile, index, sourceEncoding)
+    IOUtils.writeToFile(cssFile, css, sourceEncoding)
+    IOUtils.writeToFile(
+      packageFile,
+      packageList(coverage).toString(),
+      sourceEncoding
+    )
+    IOUtils.writeToFile(
+      overviewFile,
+      overview(coverage).toString(),
+      sourceEncoding
+    )
 
     coverage.packages.foreach(writePackage)
   }
@@ -67,15 +75,15 @@ class ScoverageHtmlWriter(
     // to com.example.html
     val file = new File(outputDir, packageOverviewRelativePath(pkg))
     file.getParentFile.mkdirs()
-    IOUtils.writeToFile(file, packageOverview(pkg).toString())
+    IOUtils.writeToFile(file, packageOverview(pkg).toString(), sourceEncoding)
     pkg.files.foreach(writeFile)
   }
 
   private def writeFile(mfile: MeasuredFile): Unit = {
     // each highlighted file is written out using the same structure as the original file.
     val file = new File(outputDir, relativeSource(mfile.source) + ".html")
     file.getParentFile.mkdirs()
-    IOUtils.writeToFile(file, filePage(mfile).toString())
+    IOUtils.writeToFile(file, filePage(mfile).toString(), sourceEncoding)
   }
 
   private def packageOverviewRelativePath(pkg: MeasuredPackage) =

reporter/src/main/scala/scoverage/reporter/ScoverageXmlWriter.scala

@@ -30,7 +30,11 @@ class ScoverageXmlWriter(
 
   def write(coverage: Coverage): Unit = {
     val file = IOUtils.reportFile(outputDir, debug)
-    IOUtils.writeToFile(file, new PrettyPrinter(120, 4).format(xml(coverage)))
+    IOUtils.writeToFile(
+      file,
+      new PrettyPrinter(120, 4).format(xml(coverage)),
+      sourceEncoding
+    )
   }
 
   private def xml(coverage: Coverage): Node = {