code: @Override
      public void execute()
      {
          if ( "pom".equals( project.getPackaging() ) )
          {
              return;
          }
  
          File baseDir = project.getBasedir();
  
          File mainScalaPath = new File( baseDir, "src/main/scala" );
          if ( mainScalaPath.isDirectory() )
          {
              String mainScalaPathStr = mainScalaPath.getAbsolutePath();
              if ( !project.getCompileSourceRoots().contains( mainScalaPathStr ) )
              {
                  project.addCompileSourceRoot( mainScalaPathStr );
                  getLog().debug( "Added source directory: " + mainScalaPathStr );
              }
          }
  
          File testScalaPath = new File( baseDir, "src/test/scala" );
          if ( testScalaPath.isDirectory() )
          {
              String testScalaPathStr = testScalaPath.getAbsolutePath();
              if ( !project.getTestCompileSourceRoots().contains( testScalaPathStr ) )
              {
                  project.addTestCompileSourceRoot( testScalaPathStr );
                  getLog().debug( "Added test source directory: " + testScalaPathStr );
              }
          }
      }
docs: Adds default Scala sources locations to Maven project.
  
  <ul>
  <li>{@code src/main/scala} is added to project's compile source roots</li>
  <li>{@code src/test/scala} is added to project's test compile source roots</li>
  </ul>