bug: null test missing for missing discriminator property.

[GregoryEssertel]

Where:

json-schema-validator/src/main/java/com/networknt/schema/OneOfValidator.java

Line 113 in eea61d6

String discriminatorPropertyValue = node.get(discriminator.getPropertyName()).asText();

To trigger:
schema:

    {
          "type": "object",
          "discriminator": { "propertyName": "name" },
          "oneOf": [
            {
              "$ref": "#/defs/Foo"
            },
            {
              "$ref": "#/defs/Bar"
            }
          ],
          "defs": {
            "Foo": {
              "type": "object",
              "properties": {
                "name": {
                  "const": "Foo"
                }
              },
              "required": [ "name" ],
              "additionalProperties": false
            },
            "Bar": {
              "type": "object",
              "properties": {
                "name": {
                  "const": "Bar"
                }
              },
              "required": [ "name" ],
              "additionalProperties": false
            }
          }
        }

value:

{}

I want to try to make a PR, what should be the expected behavior in this case. Ideas:
1 - returning an error similar to the missing required property, but specifying that it is the discriminator.
2 - ignoring discriminator and return all errors

[justin-tay]

Thanks for raising the issue.

I think the simple fix is to have it fall back on

json-schema-validator/src/main/java/com/networknt/schema/OneOfValidator.java

Lines 141 to 149 in eea61d6

	if (this.validationContext.getConfig().isOpenAPI3StyleDiscriminators()
	&& (discriminator != null || executionContext.getCurrentDiscriminatorContext().isActive())
	&& !executionContext.getCurrentDiscriminatorContext().isDiscriminatorMatchFound()) {
	errors = Collections.singleton(message().instanceNode(node).instanceLocation(instanceLocation)
	.locale(executionContext.getExecutionConfig().getLocale())
	.arguments(
	"based on the provided discriminator. No alternative could be chosen based on the discriminator property")
	.build());
	}

I don't really have an objection to a specific error message for the missing property, since the spec states If the discriminator value does not match an implicit or explicit mapping, no schema can be determined and validation SHOULD fail.

But if you want to do so then ideally the PR should have a proper fix, meaning that

• Ensure that the missing property message raised is consistent for all the discriminator usages eg. allOf, anyOf, oneOf
• The messages should all be localized (Currently even the current message isn't properly localized and would tack on an english message)

[justin-tay]

After looking at this closer it looks like due to the following

• Relaxation of the discriminator validation #436

To make the behavior consistent with the rest of the usages the logic needs to treat the discriminator as matching if the property is not present in the data and rely on the required validator to catch the missing discriminator.

I shall probably create the PR to resolve this.