JsonNumEquals fails when MissingNode is passed

[grimsa]

Problem
The following code:

JsonNode original = originalJson.at("/some/path");    // produces MissingNode instance
JsonNode updated = updatedJson.at("/some/path");
boolean valid = JsonNumEquals.getInstance().equivalent(original, updated);

results in

java.lang.NullPointerException: unhandled token type NOT_AVAILABLE
	at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:897)
	at com.github.fge.jackson.NodeType.getNodeType(NodeType.java:144)
	at com.github.fge.jackson.JsonNumEquals.doEquivalent(JsonNumEquals.java:68)
	at com.github.fge.jackson.JsonNumEquals.doEquivalent(JsonNumEquals.java:43)
	at com.google.common.base.Equivalence.equivalent(Equivalence.java:65)

The cause seems to be that there is no enum value in com.github.fge.jackson.NodeType that corresponds to MissingNode.

Workaround:

private boolean nodesEqual(JsonNode original, JsonNode updated) {
    return !oneMissing(original, updated)
            && (bothMissing(original, updated) || JsonNumEquals.getInstance().equivalent(original, updated));
}

private boolean bothMissing(JsonNode original, JsonNode updated) {
    return original.isMissingNode() && updated.isMissingNode();
}

private boolean oneMissing(JsonNode original, JsonNode updated) {
    return original.isMissingNode() ^ updated.isMissingNode();
}

[Capstan]

From the commentary in NodeType, it was intended that it be a short-lived replacement until Databind's JsonNodeType could be used, and that has an entry for MISSING.

I would be happy to review contributions of either a NodeType entry addition of MISSING, or a larger refactor to use JsonNodeType from Databind, or both, serially.

[grimsa]

For the record, we have since switched to a more generic workaround presented here: #45 (comment)