Here's an interesting "bug"

[Byron Ellis]

Hi all,

I ran into sort of an interesting issue last night. Consider the code
below. If you try to run it what will happen is you'll get a
ClassCastException on the second Filter.by. What appears to be happening is
that the Filter.by DoFnInvoker is being reused... which should be fine
since that should be working with Object... but what I can't find is where
the casting is happening because it seems like a) the cast isn't actually
needed? and b) it's doing the wrong cast. Any clues?

Best,
B

@Test
public void testReusedLambda() {
  p.apply(Create.of(new SimpleElement1()))
      .apply("First", Filter.by(Objects::nonNull))
      .apply(ParDo.of(new VerySimpleDoFn<>()))
      .apply("Second", Filter.by(Objects::nonNull));
  p.run().waitUntilFinish();
}

static class SimpleElement1 implements Serializable {}

static class SimpleElement2 implements Serializable {}

static class VerySimpleDoFn<I> extends DoFn<I, SimpleElement2> {
  @ProcessElement
  public void processElement(ProcessContext c) {
    c.output(new SimpleElement2());
  }
}