noson

A Rust library that generates example JSON data from a JSON Schema.

Given a JSON Schema as a serde_json::Value, noson produces a random JSON value that validates against it.

Usage

use rand::SeedableRng;
use rand::rngs::StdRng;
use serde_json::json;

let schema = json!({
    "type": "object",
    "properties": {
        "name": { "type": "string", "minLength": 1, "maxLength": 20 },
        "age": { "type": "integer", "minimum": 0, "maximum": 120 },
        "active": { "type": "boolean" }
    },
    "required": ["name", "age"]
});

let mut rng = StdRng::seed_from_u64(42);
let example = noson::generate(&schema, &mut rng).unwrap();

// example is a random JSON value that validates against the schema
println!("{}", serde_json::to_string_pretty(&example).unwrap());

Supported Schema Features

Types: null, boolean, string, integer, number, object, array
Constraints: minimum/maximum, exclusiveMinimum/exclusiveMaximum, minLength/maxLength, minItems/maxItems
Enum / Const: enum, const
Composition: allOf, anyOf, oneOf
References: $ref resolved against $defs / definitions
Boolean schemas: true (any value) and false (error)

Not Supported

The following JSON Schema features are not currently handled. Schemas using them will either be silently ignored (the keyword has no effect on generation) or, in the case of external $ref, return an error.

String: pattern, format, contentEncoding, contentMediaType
Numeric: multipleOf
Object: additionalProperties, patternProperties, propertyNames, minProperties, maxProperties, unevaluatedProperties
Array: prefixItems, additionalItems, contains, minContains, maxContains, uniqueItems, unevaluatedItems
Composition: not, if/then/else
Dependencies: dependentRequired, dependentSchemas
References: external $ref (http/file URIs), $dynamicRef, $anchor
Type unions: "type": ["string", "null"] (array form of type)

Roadmap

Builder/configuration API -- customizable string length ranges, array sizes, max recursion depth
format generators -- date-time, email, uri, uuid, etc.
pattern support -- regex-based string generation via rand_regex
additionalProperties generation
prefixItems, contains
minProperties / maxProperties
multipleOf
if/then/else
not
dependentRequired / dependentSchemas
External $ref resolution (http/file references)

Development