Fixes support for Maven 4 immutable API

src/it/test_no_sources/validate.groovy

@@ -1,11 +1,11 @@
-try {
-
 def file = new File(basedir, 'target')
-assert !file.exists()
 
-return true
+if (file.exists()){
+  def targetEmpty = file.listFiles()
+          .findAll { it.name != "project-local-repo" }
+          .isEmpty()
 
-} catch(Throwable e) {
-  e.printStackTrace()
-  return false
+  return targetEmpty
 }
+
+return true

src/main/java/scala_maven/ScalaDocMojo.java

@@ -64,12 +64,10 @@ public class ScalaDocMojo extends ScalaSourceMojoSupport implements MavenReport
 
   @Override
   protected List<File> getSourceDirectories() throws Exception {
-    List<String> sources = project.getCompileSourceRoots();
     // Quick fix in case the user has not added the "add-source" goal.
     String scalaSourceDir = FileUtils.pathOf(sourceDir, useCanonicalPath);
-    if (!sources.contains(scalaSourceDir)) {
-      sources.add(scalaSourceDir);
-    }
+    project.addCompileSourceRoot(scalaSourceDir);
+    List<String> sources = project.getCompileSourceRoots();
     return normalize(sources);
   }
 

src/main/java/scala_maven/ScalaTestCompileMojo.java

@@ -77,11 +77,9 @@ protected File getOutputDir() {
 
   @Override
   protected List<File> getSourceDirectories() throws Exception {
-    List<String> sources = project.getTestCompileSourceRoots();
     String scalaSourceDir = testSourceDir.getAbsolutePath();
-    if (!sources.contains(scalaSourceDir)) {
-      sources.add(scalaSourceDir);
-    }
+    project.addTestCompileSourceRoot(scalaSourceDir);
+    List<String> sources = project.getTestCompileSourceRoots();
     return normalize(sources);
   }