oneOf Validation Issue
Tim McDowell
I am working on creating a complex JSON schema and am having issues with validating a "oneOf" construction.
I have created a very simple schema using "oneOf" and a simple JSON file to demonstrate the issue.
JSON Schema:
{
"$schema": "http://json-schema.org/draft-07/schema#",
"type": "object",
"oneOf":[
{"properties": {"test1": {"type": "string"}}},
{"properties": {"test2": {"type": "number"}}}
]
}JSON File:
{
"test2":4
}When I validate the JSON file versus the schema using jsonschema.validate I expect for this to be valid. However I get the error response of:
Traceback (most recent call last):
File "TestValidate.py", line 11, in <module>
jsonschema.validate(instance=file, schema=schema, resolver=resolver)
File "C:\Python36\lib\site-packages\jsonschema\validators.py", line 899, in validate
raise error
jsonschema.exceptions.ValidationError: {'test2': 4} is valid under each of {'properties': {'test2': {'type': 'number'}}}, {'properties': {'test1': {'type': 'string'}}}
Failed validating 'oneOf' in schema:
{'$schema': 'http://json-schema.org/draft-07/schema#',
'oneOf': [{'properties': {'test1': {'type': 'string'}}},
{'properties': {'test2': {'type': 'number'}}}],
'type': 'object'}
On instance:
{'test2': 4}I don't understand how 'test2': 4 can be valid against "test1": {"type": "string"}.
Ben Hutton (@Relequestual)
Hey Tim,
This is a pretty common stumbling block here, so don’t worry.
You’re schema looks OK, but it’s not doing what you want.
You’ve assumed that the validation path should go down `oneOf[1]` and find it valid, and go down `one of[0]` and find it invalid, and so pass the overall `oneOf`.
Test your assumption.
What happens if you use the first subschema on its own?
Passes validation, right? As a result, `oneOf` is false, as it’s valid according to more than one subschema.
This is because it only expresses constraints for a property `test1`. Omission of a property key does not mean such is invalid.
`properties` only applies subschemas when the keys match, but does not place any constraint on the allowed keys of the object.
If you want to prevent additional properties in a schema, you need to use the `additionalProperties` keyword, with a value of false.
I’m addressing this common pitfall in my upcoming talk at ASC2019.
(20% off registration code: ASCSOCIAL19 if you can make it!)
Out of interest, what’s the reason for using `oneOf` here? A simplified example for demo purposes?
Feel free to use your much more complex schema and share using https://jsonschema.dev
Cheers
Ben
Tim McDowell
Ben -
Thanks for the explanation - it makes perfect sense now. Making the properties required has the same effect of forcing the check to be made.
It was a very simple example to understand how oneOf works before using it on a more complex schema. I now have that schema working as well.
Tim
---
Timothy P. McDowell Executive Vice President Thermal Energy System Specialists, LLC 3 N Pinckney St, Suite 202 Madison, WI 53703 office: 608-274-2577 cell: 608-225-5250
On 2019-09-23 10:48, Ben Hutton wrote:
Hey Tim,
This is a pretty common stumbling block here, so don’t worry.
You’re schema looks OK, but it’s not doing what you want.
You’ve assumed that the validation path should go down `oneOf[1]` and find it valid, and go down `one of[0]` and find it invalid, and so pass the overall `oneOf`.
Test your assumption.
What happens if you use the first subschema on its own?
Passes validation, right? As a result, `oneOf` is false, as it’s valid according to more than one subschema.
This is because it only expresses constraints for a property `test1`. Omission of a property key does not mean such is invalid.
`properties` only applies subschemas when the keys match, but does not place any constraint on the allowed keys of the object.
If you want to prevent additional properties in a schema, you need to use the `additionalProperties` keyword, with a value of false.
I’m addressing this common pitfall in my upcoming talk at ASC2019.
(20% off registration code: ASCSOCIAL19 if you can make it!)
Out of interest, what’s the reason for using `oneOf` here? A simplified example for demo purposes?
Feel free to use your much more complex schema and share using https://jsonschema.dev
Cheers
Ben
-- The Wellcome Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE.