jsonschema

A JSON Schema validator implementation. It compiles schema into a validation tree to have validation as fast as possible.

Supported drafts:

Draft 7 (except optional idn-hostname.json test case)
Draft 6
Draft 4 (except optional bignum.json test case)

# Cargo.toml
jsonschema = "0.14"

To validate documents against some schema and get validation errors (if any):

use jsonschema::JSONSchema;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    let compiled = JSONSchema::compile(&schema)
        .expect("A valid schema");
    let result = compiled.validate(&instance);
    if let Err(errors) = result {
        for error in errors {
            println!("Validation error: {}", error);
            println!(
                "Instance path: {}", error.instance_path
            );
        }
    }
}

Each error has an instance_path attribute that indicates the path to the erroneous part within the validated instance. It could be transformed to JSON Pointer via .to_string() or to Vec<String> via .into_vec().

If you only need to know whether document is valid or not (which is faster):

use jsonschema::is_valid;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    assert!(is_valid(&schema, &instance));
}

Or use a compiled schema (preferred):

use jsonschema::JSONSchema;
use serde_json::json;

fn main() {
    let schema = json!({"maxLength": 5});
    let instance = json!("foo");
    // Draft is detected automatically
    // with fallback to Draft7
    let compiled = JSONSchema::compile(&schema)
        .expect("A valid schema");
    assert!(compiled.is_valid(&instance));
}

Output styles

jsonschema supports basic & flag output styles from Draft 2019-09, so you can serialize the validation results with serde:

use jsonschema::{Output, BasicOutput, JSONSchema};

fn main() {
    let schema_json = serde_json::json!({
        "title": "string value",
        "type": "string"
    });
    let instance = serde_json::json!{"some string"};
    let schema = JSONSchema::options()
        .compile(&schema_json)
        .expect("A valid schema");
    
    let output: BasicOutput = schema.apply(&instance).basic();
    let output_json = serde_json::to_value(output)
        .expect("Failed to serialize output");
    
    assert_eq!(
        output_json, 
        serde_json::json!({
            "valid": true,
            "annotations": [
                {
                    "keywordLocation": "",
                    "instanceLocation": "",
                    "annotations": {
                        "title": "string value"
                    }
                }
            ]
        })
    );
}

Status

This library is functional and ready for use, but its API is still evolving to the 1.0 API.

Bindings

Python - See the ./bindings/python directory
Ruby - a crate by @driv3r
NodeJS - a package by @ahungrynoob

Performance

There is a comparison with other JSON Schema validators written in Rust - jsonschema_valid==0.4.0 and valico==3.6.0.

Test machine i8700K (12 cores), 32GB RAM.

Input values and schemas:

Zuora OpenAPI schema (zuora.json). Validated against OpenAPI 3.0 JSON Schema (openapi.json).
Kubernetes Swagger schema (kubernetes.json). Validated against Swagger JSON Schema (swagger.json).
Canadian border in GeoJSON format (canada.json). Schema is taken from the GeoJSON website (geojson.json).
Concert data catalog (citm_catalog.json). Schema is inferred via infers-jsonschema & manually adjusted (citm_catalog_schema.json).
Fast is taken from fastjsonschema benchmarks (fast_schema.json, fast_valid.json and fast_invalid.json).

Case	Schema size	Instance size
OpenAPI	18 KB	4.5 MB
Swagger	25 KB	3.0 MB
Canada	4.8 KB	2.1 MB
CITM catalog	2.3 KB	501 KB
Fast (valid)	595 B	55 B
Fast (invalid)	595 B	60 B

Here is the average time for each contender to validate. Ratios are given against compiled JSONSchema using its validate method. The is_valid method is faster, but gives only a boolean return value:

Case	jsonschema_valid	valico	jsonschema (validate)	jsonschema (is_valid)
OpenAPI	- (1)	- (1)	4.717 ms	4.279 ms (x0.90)
Swagger	- (2)	83.357 ms (x12.47)	6.681 ms	4.533 ms (x0.67)
Canada	32.987 ms (x31.38)	141.41 ms (x134.54)	1.051 ms	1.046 ms (x0.99)
CITM catalog	4.735 ms (x2.00)	13.222 ms (x5.58)	2.367 ms	535.07 us (x0.22)
Fast (valid)	2.00 us (x3.85)	3.18 us (x6.13)	518.39 ns	97.91 ns (x0.18)
Fast (invalid)	339.28 ns (x0.50)	3.34 us (x5.00)	667.55 ns	5.41ns (x0.01)

Notes:

jsonschema_valid and valico do not handle valid path instances matching the ^\\/ regex.
jsonschema_valid fails to resolve local references (e.g. #/definitions/definitions).

You can find benchmark code in benches/jsonschema.rs, Rust version is 1.57.

Support