Remove properties from JSON object not present in schema?

Question

I am using Python's jsonschema to validate JSON files against a schema. It works great. But now I need to remove any properties from my JSON that are not present in the schema.

I know that according to the JSON Schema docs, I can set the property:

additionalProperties = false

to reject any files with additional properties. But this will just reject the properties, not actually remove them.

What is the best way to remove them?

I guess I can write my own script that:

walks every leaf node of the JSON file
checks whether the leaf node exists in the schema
if it does not, walks up the tree until it finds the highest node that does exist, then prunes the branch at that point.

My question is: is there an existing Python library to do this, or do I need to write one? I have Googled, but without any success.

I'm also interested in this use case and opened a GitHub Issue. — Daniel Himmelstein
– Daniel Himmelstein, Commented Aug 7, 2018 at 19:32
got the same issue in ruby : stackoverflow.com/questions/60569726/… — gordie
– gordie, Commented Mar 8, 2020 at 20:12

Raphael Medaer · Accepted Answer · 2020-03-28 21:10:44Z

3

You could extend the validator. A similar implementation is used for default values.

A little bit late, but here is a solution.

I extend the validator to override validation of properties keyword. If one of properties exists in instance but not in the schema, I remove it from the instance.

from jsonschema import Draft7Validator, validators

def extend_validator(validator_class):
    validate_properties = validator_class.VALIDATORS["properties"]

    def remove_additional_properties(validator, properties, instance, schema):
        for prop in list(instance.keys()):
            if prop not in properties:
                del instance[prop]

        for error in validate_properties(
            validator, properties, instance, schema,
        ):
            yield error

    return validators.extend(
        validator_class, {"properties" : remove_additional_properties},
    )

DefaultValidatingDraft7Validator = extend_validator(Draft7Validator)

# Example usage:
obj = {
    'foo': 'bar',
    'not_in_schema': 'no no no'
}
schema = {
    'properties': {
        'foo': {
            'type': 'string'
        }
    }
}

DefaultValidatingDraft7Validator(schema).validate(obj)
assert obj == {'foo': 'bar'}

answered Mar 28, 2020 at 21:10

Raphael Medaer

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1 Comment

Raphael Medaer Over a year ago

@Richard does it fix your issue ?

Raymond Hettinger · Accepted Answer · 2020-01-27 08:12:08Z

0

I don't see a straight-forward way to achieve this without monkey patching the iter_errors() method in the Validator class:

https://github.com/Julian/jsonschema/blob/master/jsonschema/validators.py#L296

answered Jan 27, 2020 at 8:12

Raymond Hettinger

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