OpenAPI schema validator

A JSON schema validator for OpenAPI specifications, it currently supports:

• 2.0
• 3.0.x
• 3.1.x

Tested on over 2,000 real-world APIs from AWS, Microsoft, Google etc.

Install

npm install @seriousme/openapi-schema-validator

Usage

// ESM
import Validator from "@seriousme/openapi-schema-validator";
// CommonJS
const Validator = require("@seriousme/openapi-schema-validator");

console.log(Validator.supportedVersions.has("3.1"));
// prints true

const validator = new Validator();
const res = await validator.validate("./petstore.json");
const specification = validator.specification;
// specification now contains a Javascript object containing the specification
if (res.valid) {
  console.log("Specification matches schema for version", validator.version);
  const schema = validator.resolveRefs();
  // schema now contains a Javascript object containing the dereferenced schema
} else {
  console.log("Specification does not match Schema");
  console.log(res.errors);
}

CLI

Run with global install:

npm install @seriousme/openapi-schema-validator -g
validate-api <filename>

Run without install:

npx -p @seriousme/openapi-schema-validator validate-api <filename>

Where <filename> refers to a YAML or JSON file containing the specification.

API

• new Validator(ajvOptions)
• <instance>.validate(specification)
• <instance>.specification
• <instance>.version
• <instance>.resolveRefs(options)
• <instance>.addSpecRef(uri, subSpecification)
• Validator.supportedVersions

new Validator(ajvOptions)

The constructor returns an instance of Validator. By passing an ajv options object it is possible to influence the behavior of the AJV schema validator. AJV fails to process the openApi schemas if you set strict:true therefore this set to false if present. This is not a bug but a result of the complexity of the openApi JSON schemas.

<instance>.validate(specification)

This function tries to validata a specification against the OpenApi schemas. specification can be one of:

• a JSON object
• a JSON object encoded as string
• a YAML string
• a filename

External references are not automatically resolved so you need to inline them yourself if required e.g by using <instance>.addSpecRef() The result is an object:

{
  valid: <boolean>,
  errors: <any>  // only present if valid is false
}

<instance>.specification

If the validator managed to extract data from the specification parameter then the extracted specification is available in this property as javascript object. E.g. if you supplied a filename of a YAML file and the file was sucessfully read and its YAML decoded then the contents is here. Even if validation failed.

<instance>.version

If validation is succesfull this will return the openApi version found e.g. ("2.0","3.0","3.1). The openApi specification only specifies major/minor versions as separate schemas. So "3.0.3" results in "3.0".

<instance>.resolveRefs(options)

This function tries to resolve all internal references. External references are not automatically resolved so you need to inline them yourself if required e.g by using <instance>.addSpecRef(). By default it will use the last specification passed to <instance>.validate() but you can explicity pass a specification by passing {specification:<object>} as options. The result is an object where all references have been resolved. Resolution of references is shallow This should normally not be a problem for this use case.

<instance>.addSpecRef(subSpecification, uri)

subSpecification can be one of:

• a JSON object
• a JSON object encoded as string
• a YAML string
• a filename uri must be a string (e.g. http://www.example.com/subspec), but is not required if the subSpecification holds a $id attribute at top level. If you specify a value for uri it will overwrite the definition in the $id attribute at top level.

Sometimes a specification is composed of multiple files that each contain parts of the specification. The specification refers to these sub specifications using external references. Since references are based on URI's (so Identifier and Location as in URL's!) there needs to be a way to tell the validator how to resolve those references. This is where this function comes in:

E.g.: we have a main specification in main-spec.yaml containing:

...
paths:
  /pet:
    post:
      tags:
        - pet
      summary: Add a new pet to the store
      description: ''
      operationId: addPet
      responses:
        '405':
          description: Invalid input
      requestBody:
        $ref: 'http://www.example.com/subspec#/components/requestBodies/Pet'

And the reference is in sub-spec.yaml, containing:

components:
  requestBodies:
    Pet:
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Pet'
        application/xml:
          schema:
            $ref: '#/components/schemas/Pet'
      description: Pet object that needs to be added to the store
      required: true
  ...

Then the validation can be performed as follows:

const validator = new Validator();
await validator.addSpecRef("./sub-spec.yaml", "http://www.example.com/subspec");
const res = await validator.validate("./main-spec.yaml");
// res now contains the results of the validation across main-spec and sub-spec
const specification = validator.specification;
// specification now contains a Javascript object containing the specification
// with the subspec inlined

Validator.supportedVersions

This static property returns the OpenApi versions supported by this package as a Set. If present, the result of <instance>.version is a member of this Set.

License

Licensed under the MIT license