Iterating over an array stream from an object field which has been mapped throws an IllegalStateException

[tomwhoiscontrary]

Say you have some JSON which defines an object, and inside that object there is an array. You parse to the start of the array, then call JsonParser#getArrayStream, then call Stream#map on that to transform it somehow, then call Stream#iterator on the result, and iterate over the iterator.

I think this should result in iterating over the transformed elements of the array.

However, it throws an IllegalStateException from the hasNext call at the end of the iteration.

This code (the body of a JUnit 5 test):

        try (JsonParser parser = Json.createParser(new StringReader("{\"numbers\": [1, 2, 3]}"))) {
            assertThat(parser.next(), equalTo(JsonParser.Event.START_OBJECT));
            assertThat(parser.next(), equalTo(JsonParser.Event.KEY_NAME));
            assertThat(parser.getString(), equalTo("numbers"));
            assertThat(parser.next(), equalTo(JsonParser.Event.START_ARRAY));

            Stream<JsonValue> numbersStream = parser.getArrayStream().map(Function.identity());
            Iterator<JsonValue> numbersIterator = numbersStream.iterator();

            List<Integer> numbersList = new ArrayList<>();
            while (numbersIterator.hasNext()) {
                numbersList.add(((JsonNumber) numbersIterator.next()).intValue());
            }

            assertThat(numbersList, equalTo(List.of(1, 2, 3)));
        }

Throws this exception:

java.lang.IllegalStateException: getValue() was called in illegal parser event END_OBJECT.
	at org.leadpony.joy.core.AbstractJsonParser.newIllegalStateException(AbstractJsonParser.java:234)
	at org.leadpony.joy.core.AbstractJsonParser.getValue(AbstractJsonParser.java:87)
	at org.leadpony.joy.core.JsonStreams$1.tryAdvance(JsonStreams.java:46)
	at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.lambda$initPartialTraversalState$0(StreamSpliterators.java:292)
	at java.base/java.util.stream.StreamSpliterators$AbstractWrappingSpliterator.fillBuffer(StreamSpliterators.java:206)
	at java.base/java.util.stream.StreamSpliterators$AbstractWrappingSpliterator.doAdvance(StreamSpliterators.java:169)
	at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.tryAdvance(StreamSpliterators.java:298)
	at java.base/java.util.Spliterators$1Adapter.hasNext(Spliterators.java:681)

Using Joy 2.1.0 on OpenJDK 17+35.

Note that the Stream#map call takes Function.identity() as a parameter. If you remove the map call, this code is semantically the same, but now it works - it doesn't throw an exception, and the test passes.