@Override
    public CharSequence readSource(JavaFileObject filename) {
        try {
            inputFiles.add(filename);
            boolean prev = bark.setDiagnosticsIgnored(true);
            try {
                return filename.getCharContent(false);
            }
            finally {
                bark.setDiagnosticsIgnored(prev);
            }
        } catch (IOException e) {
            bark.error(Position.NOPOS, "cant.read.file", filename);
            return null;
        }
    }