json_schema_fuzz

Schema-guided JSON value generation for Draft 2020-12 JSON Schema documents.

Installation

Add to your Cargo.toml:

[dependencies]
json_schema_fuzz = "0.2.6"

Usage

use json_schema_ast::SchemaDocument;
use json_schema_fuzz::{GenerationConfig, ValueGenerator};
use serde_json::json;

let raw = json!({
    "type": "object",
    "properties": {
        "flag": { "type": "boolean" },
        "count": { "type": "integer" }
    },
    "required": ["flag"]
});

// Keep the schema document around; it lazily builds the canonicalized graph
// and raw validator when generation needs them.
let schema = SchemaDocument::from_json(&raw).unwrap();

// Generate a random value with the default depth and retry budget.
let mut rng = rand::rng();
let value = ValueGenerator::generate(&schema, GenerationConfig::default(), &mut rng).unwrap();

println!("{}", value);

For repeated generation from the same schema, keep the same SchemaDocument so its lazy canonical graph and raw validator are reused.

Public Interface

• ValueGenerator::generate(&SchemaDocument, GenerationConfig, rng) -> Result<Value, GenerateError> is the value-generation entry point.
• GenerationConfig::default() uses the default recursion depth and retry budget.
• GenerationConfig::new(depth) changes the recursion depth limit while keeping the default retry budget.
• GenerationConfig::with_max_generation_attempts(limit) overrides the retry budget with a non-zero limit.
• GenerateError::Unsatisfiable means the resolved schema is known to have no valid instances.
• GenerateError::ExhaustedAttempts means the schema may still be satisfiable, but the heuristic generator did not find a raw-valid candidate within the configured retry budget.

The generator walks the canonicalized SchemaNode graph from json_schema_ast, but every returned value is accepted by SchemaDocument::is_valid() against the original raw schema.

License

Licensed under MIT. See LICENSE.