code: @GwtIncompatible("Unnecessary")
    private void outputSourceMap(B options, String associatedName) throws IOException {
      if (Strings.isNullOrEmpty(options.sourceMapOutputPath)
          || options.sourceMapOutputPath.equals("/dev/null")) {
        return;
      }
  
      String outName = expandSourceMapPath(options, null);
      maybeCreateDirsForPath(outName);
      try (Writer out = fileNameToOutputWriter2(outName)) {
        compiler.getSourceMap().appendTo(out, associatedName);
      }
    }
docs: Outputs the source map found in the compiler to the proper path if one exists.
  
  @param options The options to the Compiler.