Jackson 3 parses YAML ~ as StringNode instead of NullNode

[neottil]

In Jackson 2, the special character ~ was parsed as a NullNode, while in Jackson 3 I get a StringNode with value ~. It seems that the default behavior has changed.

I tried several YAML mapper configurations, but I couldn’t find any setting that reproduces the Jackson 2 behavior.

The issue can be reproduced with the following test:

@Test
void tilde() throws JsonProcessingException {
    String rawDescriptor = """
         specVersion: v1
         kind: com.example.kind
         name: "mnp_up"
         state: ~
         description: "a description"
        """;

    tools.jackson.dataformat.yaml.YAMLMapper myYamlMapper = new YAMLMapper();
    JsonNode node1 = myYamlMapper.readValue(rawDescriptor, tools.jackson.databind.JsonNode.class);
    com.fasterxml.jackson.databind.ObjectMapper objectMapper = new com.fasterxml.jackson.databind.ObjectMapper(new YAMLFactory());
    com.fasterxml.jackson.databind.JsonNode node2 = objectMapper.readValue(rawDescriptor, com.fasterxml.jackson.databind.JsonNode.class);
    System.out.println("node1 state: " + node1.get("state").getNodeType() + "\nnode2 state: " + node2.get("state").getNodeType());
}

OUTPUT:
node1 state: STRING
node2 state: NULL

I couldn’t find anything about this in the migration documentation.

Since my application logic depends on parsing files that may contain this special character, I need to stay compatible with the behavior implemented in Jackson 2.

How can I configure the Jackson 3 mapper to get the same result as in Jackson 2?

[yawkat]

Please see #506 (comment)

[cowtowncoder]

I don't think #506 is directly relevant as it's about ~ as null Map/Object key, whereas here it's for value.

And it would appear this was an intended change: plain ~ as value should, I think, be seen as null value, not String.

Will investigate.

[yawkat]

Yes the issue I linked isn't the same but the comments explain why the change happened aiui.

[cowtowncoder]

Ah. Yes, that makes sense... too bad things again get this complicated. :-/

[neottil]

Hi, @cowtowncoder any update on this issue?

[cowtowncoder]

@neottil No. I don't quite know how to approach this, given YAML spec differences (1.1 vs 1.2; SnakeYAML vs snakeyaml-engine).