`ArrayNode.addAll()` adds raw `null` values which cause NPE on `deepCopy()` and `toString()`

[heshamMassoud]

Version: 2.9.9

When I create an ArrayNode and use ArrayNode#addAll to add elements containing a raw null element as follows:

final List<ObjectNode> nodes = Arrays.asList(null, JsonNodeFactory.instance.objectNode());
final ArrayNode arrayNode = JsonNodeFactory.instance.arrayNode();
arrayNode.addAll(nodes);

Calling ArrayNode#deepCopy and ArrayNode#toString on such arrayNode will throw NullPointerExceptions.

However, if we add the nodes using ArrayNode#add as follows:

final ArrayNode arrayNode = JsonNodeFactory.instance.arrayNode();
arrayNode.add((JsonNode) null);
arrayNode.add(JsonNodeFactory.instance.objectNode());

Calling ArrayNode#deepCopy and ArrayNode#toString on such arrayNode will NOT throw any NullPointerExceptions.

This is because ArrayNode#add converts any raw null to a NullNode object:

jackson-databind/src/main/java/com/fasterxml/jackson/databind/node/ArrayNode.java

Lines 306 to 313 in f75b304

	public ArrayNode add(JsonNode value)
	{
	if (value == null) { // let's not store 'raw' nulls but nodes
	value = nullNode();
	}
	_add(value);
	return this;
	}

But ArrayNode#addAll does not. But It should, otherwise how does one deepCopy an arrayNode that contains null raw elements?

[cowtowncoder]

First of all: thank you for reporting the issue! Yes, that looks like a problem, although surprisingly one that has not been reported before. I agree that raw null is not to be added; and to me it seems there are 2 possibilities: either automatically "upgrade" null as is done in a few other places, or throw an exception to indicate invalid value.

It seems reasonable to expect former, so that nulls would be automatically coerced, given that this happens elsewhere.

I'll think about this bit more, and will get fixed for 2.10 to be included in 2.10.0.

[heshamMassoud]

Hi @cowtowncoder, thanks for the quick reply. I also agree with you about the former being the more suitable solution to be consistent with the rest of the methods.

I attempted to provide a fix for it here: #2443