public long copyTo(CharSink sink) throws IOException {
    checkNotNull(sink);

    Closer closer = Closer.create();
    try {
      Reader reader = closer.register(openStream());
      Writer writer = closer.register(sink.openStream());
      return CharStreams.copy(reader, writer);
    } catch (Throwable e) {
      throw closer.rethrow(e);
    } finally {
      closer.close();
    }
  }

  /**

  public long copyTo(CharSink sink) throws IOException {
    checkNotNull(sink);

    Closer closer = Closer.create();
    try {
      Reader reader = closer.register(openStream());
      Writer writer = closer.register(sink.openStream());
      return CharStreams.copy(reader, writer);
    } catch (Throwable e) {
      throw closer.rethrow(e);
    } finally {
      closer.close();
    }
  }

  /**

    ByteSource checker =
        new ByteSource() {
          @Override
          public InputStream openStream() throws IOException {
            if (counter[0]++ != 0) {
              throw new IllegalStateException("More than one source open");
            }
            return new FilterInputStream(source.openStream()) {
              @Override
              public void close() throws IOException {
                super.close();

    ByteSource checker =
        new ByteSource() {
          @Override
          public InputStream openStream() throws IOException {
            if (counter[0]++ != 0) {
              throw new IllegalStateException("More than one source open");
            }
            return new FilterInputStream(source.openStream()) {
              @Override
              public void close() throws IOException {
                super.close();

   */
  public abstract InputStream openStream() throws IOException;

  /**
   * Opens a new buffered {@link InputStream} for reading from this source. The returned stream is
   * not required to be a {@link BufferedInputStream} in order to allow implementations to simply
   * delegate to {@link #openStream()} when the stream returned by that method does not benefit from

    advance();
  }

  /** Closes the current reader and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      current = it.next().openStream();
    }
  }

  @Override
  public int read(char[] cbuf, int off, int len) throws IOException {
    checkNotNull(cbuf);
    if (current == null) {
      return -1;
    }

            project.setOriginalModel(model);
            ConsumerPomArtifactTransformer t = new ConsumerPomArtifactTransformer((s, p, f) -> {
                try (InputStream is = f.openStream()) {
                    return DefaultConsumerPomBuilder.transformPom(new MavenStaxReader().read(is), project);
                }
            });

                @Override
                public String getLocation() {
                    return "test-pom.xml";
                }

                @Override
                public InputStream openStream() throws IOException {
                    return null;
                }

                @Override
                public Source resolve(String relative) {
                    return null;
                }

        String content = "test content";
        Files.writeString(testFile, content);

        Source source = Sources.fromPath(testFile);
        try (InputStream inputStream = source.openStream()) {
            String readContent = new String(inputStream.readAllBytes());
            assertEquals(content, readContent);
        }
    }

    @Test
    void testNullHandling() {

        ModelSource source = new ModelSource() {
            @Override
            public Path getPath() {
                return actual;
            }

            @Override
            public InputStream openStream() throws IOException {
                return Files.newInputStream(actual);
            }

            @Override
            public String getLocation() {
                return actual.toString();