not : Schema
not
SchemaAn instance is valid against this keyword if it fails to validate successfully against the schema defined by this keyword.
| Value | This keyword must be set to a valid JSON Schema |
|---|---|
| Kind | Applicator |
| Applies To | Any |
| Base Dialect | 2020-12 |
| Changed In | None |
| Introduced In | Draft 4 |
| Vocabulary | Applicator |
| Specification | https://json-schema.org/draft/2020-12/json-schema-core.html#section-10.2.1.4 |
| Metaschema | https://json-schema.org/draft/2020-12/meta/applicator |
| Official Tests | draft2020-12/not.json |
| Default |
false
|
| Annotation | None |
| Affected By | None |
| Affects | None |
| Also See |
|
The not keyword restricts instances to fail validation against the given subschema. This keyword represents a logical negation (NOT) operation. In other words, the instance successfully validates against the schema only if it does not match the given subschema.
Digging Deeper
After evaluating this keyword, any annotation emitted by its subschema is discarded, independently of whether the subschema was successful or not, as annotations are always discarded on failure. While this might seem counter-intuitive, consider the following cases:
- If the subschema successfully validates against the instance, then the negation keyword itself fails and annotations are discarded
- If the subschema fails to validate against the instance, then annotations are discarded before bubbling up to the outer negation keyword
Best Practice
Avoid the use of this keyword (usually negating the
required keyword) to prohibit
specific object properties from being defined. Instead, use the
properties keyword and set the disallowed object
properties to the false boolean schema.
This keyword is equivalent to the ! operator found in most programming
languages. For example:
bool valid = !not_schema;
Examples
A schema that constrains instances to not be a specific value
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"not": {
"title": "I will never be emitted as an annotation",
"const": "Prohibited"
}
}
Valid
A value that does not equal the prohibited value is valid and no annotation is emitted
Instance
"Hello World"
Invalid
A value that equals the prohibited value is invalid
Instance
"Prohibited"
A schema that negates an unsatisfiable schema matches every possible instance
Schema
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"not": {
"type": "string",
"minLength": 10,
"maxLength": 9
}
}
Valid
Any value is valid
Instance
"Hello World"