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@exodus/schemasafe

A code-generating JSON Schema validator that attempts to be reasonably secure.

Supports draft-04/06/07/2019-09/2020-12 and the discriminator OpenAPI keyword.

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Features

Installation

npm install --save @exodus/schemasafe

Usage

Simply pass a schema to compile it:

const { validator } = require('@exodus/schemasafe')

const validate = validator({
  type: 'object',
  required: ['hello'],
  properties: {
    hello: {
      type: 'string'
    }
  }
})

console.log('should be valid', validate({ hello: 'world' }))
console.log('should not be valid', validate({}))

Or use the parser API (running in strong mode by default):

const { parser } = require('@exodus/schemasafe')

const parse = parser({
  $schema: 'https://json-schema.org/draft/2019-09/schema',
  type: 'object',
  required: ['hello'],
  properties: {
    hello: {
      pattern: '^[a-z]+$',
      type: 'string'
    }
  },
  additionalProperties: false
})

console.log(parse('{"hello": "world" }')) // { valid: true, value: { hello: 'world' } }
console.log(parse('{}')) // { valid: false }

Parser API is recommended, because this way you can avoid handling unvalidated JSON objects in non-string form at all in your code.

Options

See options documentation for the full list of supported options.

Custom formats

@exodus/schemasafe supports the formats specified in JSON schema v4 (such as date-time). If you want to add your own custom formats pass them as the formats options to the validator:

const validate = validator({
  type: 'string',
  format: 'no-foo'
}, {
  formats: {
    'no-foo': (str) => !str.includes('foo'),
  }
})
console.log(validate('test')) // true
console.log(validate('foo')) // false

const parse = parser({
  $schema: 'https://json-schema.org/draft/2019-09/schema',
  type: 'string',
  format: 'only-a'
}, {
  formats: {
    'only-a': /^a+$/,
  }
})
console.log(parse('"aa"')) // { valid: true, value: 'aa' }
console.log(parse('"ab"')) // { valid: false }

External schemas

You can pass in external schemas that you reference using the $ref attribute as the schemas option

const ext = {
  type: 'string'
}

const schema = {
  $ref: 'ext#' // references another schema called ext
}

// pass the external schemas as an option
const validate = validator(schema, { schemas: { ext: ext }})

console.log(validate('hello')) // true
console.log(validate(42)) // false

schemas can be either an object as shown above, a Map, or plain array of schemas (given that those have corresponding $id set at top level inside schemas themselves).

Enabling errors shows information about the source of the error

When the includeErrors option is set to true, @exodus/schemasafe also outputs:

const schema = {
  type: 'object',
  required: ['hello'],
  properties: {
    hello: {
      type: 'string'
    }
  }
}
const validate = validator(schema, { includeErrors: true })

validate({ hello: 100 });
console.log(validate.errors)
// [ { keywordLocation: '#/properties/hello/type', instanceLocation: '#/hello' } ]

Or, similarly, with parser API:

const schema = {
  $schema: 'https://json-schema.org/draft/2019-09/schema',
  type: 'object',
  required: ['hello'],
  properties: {
    hello: {
      type: 'string',
      pattern: '^[a-z]+$',
    }
  },
  additionalProperties: false,
}
const parse = parser(schema, { includeErrors: true })

console.log(parse('{ "hello": 100 }'));
// { valid: false,
//   error: 'JSON validation failed for type at #/hello',
//   errors: [ { keywordLocation: '#/properties/hello/type', instanceLocation: '#/hello' } ]
// }

Only the first error is reported by default unless allErrors option is also set to true in addition to includeErrors.

See Error handling for more information.

Generate Modules

See the doc/samples directory to see how @exodus/schemasafe compiles supported test suites.

To compile a validator function to an IIFE, call validate.toModule():

const { validator } = require('@exodus/schemasafe')

const schema = {
  type: 'string',
  format: 'hex'
}

// This works with custom formats as well.
const formats = {
  hex: (value) => /^0x[0-9A-Fa-f]*$/.test(value),
}

const validate = validator(schema, { formats })

console.log(validate.toModule())
/** Prints:
 * (function() {
 * 'use strict'
 * const format0 = (value) => /^0x[0-9A-Fa-f]*$/.test(value);
 * return (function validate(data) {
 *   if (data === undefined) data = null
 *   if (!(typeof data === "string")) return false
 *   if (!format0(data)) return false
 *   return true
 * })})();
 */

Performance

@exodus/schemasafe uses code generation to turn a JSON schema into javascript code that is easily optimizeable by v8 and extremely fast.

See Performance for information on options that might affect performance both ways.

Contributing

Get a fully set up development environment with:

git clone https://github.com/ExodusMovement/schemasafe
cd schemasafe

git submodule update --init --recursive
yarn
yarn lint
yarn test

Previous work

This is based on a heavily rewritten version of the amazing (but outdated) is-my-json-valid by @mafintosh.

Compared to is-my-json-valid, @exodus/schemasafe adds security-first design, many new features, newer spec versions support, slimmer and more maintainable code, 0 dependencies, self-contained JS module generation, fixes bugs and adds better test coverage, and drops support for outdated Node.js versions.

License

MIT