OneOf Validation removes validations, making invalid data appear valid

[kamtschatka]

We are working on validating an array of different kinds of events, that are distinguished by an "event.type" property.
For a reproducer, I have recreated it with a "pet_type" property.
There is the type Cat and Dog. If I just put them as possible types into the array, the passed in JSON gets validated against each type separately and we will get all validation errors for all types, which makes the error very hard to find.
To narrow it down, we are using "if/then/else" to narrow down the type based on the "pet_type" beforehand:

{
	"title": "PetArray",
	"type": "object",
	"properties": {
		"pets": {
			"type": "array",
			"items": {
				"oneOf": [
					{
						"if": {
							"properties": {
								"pet_type": {
									"const": "Cat"
								}
							}
						},
						"then": {
							"type": "object",
							"properties": {
								"hunts": {
									"type": "boolean"
								},
								"age": {
									"type": "integer"
								}
							},
							"required": [
								"age"
							]
						},
						"else": false
					},
					{
						"if": {
							"properties": {
								"pet_type": {
									"const": "Dog"
								}
							}
						},
						"then": {
							"type": "object",
							"properties": {
								"bark": {
									"type": "boolean"
								},
								"breed": {
									"type": "string"
								}
							},
							"required": [
								"bark"
							]
						},
						"else": false
					}
				]
			}
		}
	},
	"additionalProperties": false,
	"required": [
		"pets"
	]
}

I then pass in this JSON for validations:

{
	"pets": [
      {
       "pet_type": "Cat",
        "hunts": "asdf",
        "additionaValue": "asdf"
      }
    ]
}

What I expect it to complain about:

• "hunts" is a string and not a boolean
• "age" is missing completely
• optional: "it also does not match the "false" condition at the end

When I run this on https://www.jsonschemavalidator.net/, everything shows up as expected.

When I run it with the json-schema-validator, the only message I get is "Boolean schema false is not valid". This is basically the optional error I have listed above.

When I debug through the validator, I can see that the "OneOfValidator" actually detects the problem with the "age" property being required, when it is missing. The validation error gets filtered out in the OneOfValidator though, because of #535.

The problem with "hunts" being a string and not a boolean is also detected and filtered out, but I did not debug into it further.

In my opinion the change for issue 535 is invalid and should be removed again. The JSON does not match against either of the provided schemas, so all the errors should be shown. https://www.jsonschemavalidator.net shows the same outcome as json-schema-validator showed before the change.

To get a better validation result for the sample from issue 535, the "if/then/else" mechanism should probably be used.

[stevehu]

@kamtschatka I have reviewed the changes for #535 and the fix makes sense. Could you please elaborate a little bit more on what was wrong with that PR? Or better yet, summit a PR to help the discussion? Thanks.

[kamtschatka]

The fix only makes sense for this particular use case, and only because the schema in the sample for #535 is not created properly.
The basic issue was that the validator did not narrow down the validation, because the schema did not tell it to do so.

The schema said the following:
It must either be of type 1 or 2. When the passed in event did not match the description for either one of the types, it showed the error messages for both of them (which is also what https://www.jsonschemavalidator.net/ does and what I would expect)

What you can however do is the following:
If the schema has property 1 then it MUST be of type 1 and therefore the validation needs to only perform validations for type 1 and not show validation errors for type 2

This change for #535 tries to perform some magic in the validations to narrow it down(which is not actually specified in the schema definiton), which breaks the validation results for other scenarios.

[stevehu]

I am with you. We shouldn't have customized code to handle a particular scenario. Is it possible for you to submit a PR to get it fixed? Thanks.

[fdutton]

@kamtschatka Do these messages meet your needs?

json-schema-validator/src/test/resources/draft7/issue653.json

Lines 82 to 86 in 284e952

	"validationMessages": [
	"$.pets[0]: should be valid to one and only one schema, but 0 are valid",
	"$.pets[0].age: is missing but it is required",
	"Boolean schema false is not valid"
	]

[kamtschatka]

The first 2 look good, but I am wondering why the third one is there? The "false" condition is part of the else branch, so shouldn't it be omittted?
Edit: just realized it is from the other validation. Looks good to me.

[fdutton]

I updated the OneOfValidator; I still have to tackle the IfValidator. If this is good for you, I'll close this issue. It would be nice if you reported another issue on what you expect from if-then-else validation.

[fdutton]

Closing as resolved