Use Ajv to validate OpenAPI component schemas

Question

I am getting an error when using Ajv to load a schema that uses $ref imported from a yaml file inside an OpenAPI description.

This is my yaml file:

    openapi: 3.0.3
    info:
      title: Demo
      version: 1.0.0
    paths:
      /carousel:
        get:
          responses:
            "200":
              description: Successful operation
              content:
                application/json:
                  schema:
                    type: array
                    items:
                      $ref: "#/components/schemas/test"
    components:
      schemas:
        other:
          type: object
          properties:
            component:
              type: object
        test:
          type: object
          properties:
            slides:
              type: array
              items:
                type: object
                properties:
                  contents:
                    type: array
                    items:
                      anyOf:
                        - $ref: "#/components/schemas/other"

This is my code (JS + Vite)

    import Ajv from 'ajv'
    import YamlContent from '../Config/API.yaml'; //vite.config.js with package @modyfi/vite-plugin-yaml
    const validate =
      new Ajv({
        schemas: YamlContent.components.schemas
      }).
      getSchema(YamlContent.components.schemas.test);

I also tried:

    const validate =
      new Ajv().
      addSchema(YamlContent.components.schemas.other).
      compile(YamlContent.components.schemas.test);

But it always gives the same error. What am i missing here? Thanks.

Answer 1

no reason to use anyOf for a single schema, just pass that schema as the reference

API.yaml

openapi: 3.0.3
info:
  title: Demo
  version: 1.0.0
paths:
  /carousel:
    get:
      responses:
        "200":
          description: Successful operation
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/test"
components:
  schemas:
    other:
      type: object
      properties:
        component:
          type: object
    test:
      type: object
      properties:
        slides:
          type: array
          items:
            type: object
            properties:
              contents:
                type: array
                items:
                  $ref: "#/components/schemas/other"

OpenAPI 3.0.x requires the use of ajv-draft-04 and the ajv-formats packages.

Because you are using a yaml file, you need a way to load it with js-yaml

package.json

{
    "dependencies": {
        "ajv": "^8",
        "ajv-draft-04": "^1.0.0",
        "js-yaml": "^4.1.0",
        "ajv-formats": "^2.1.1"
    }
}

We use strict:false to make sure the ajv validator abides by the JSON Schema specification correctly.

The idea is to use the addSchema() method to add the entire OpenAPI description; then use the validate function and provide an object schema with a $ref to the component schema you want to validate against in the first argument and pass the data instance as the second argument. Then output the results.

index.js

const Ajv = require('ajv-draft-04')
const addFormats = require('ajv-formats')
const fs = require('fs')
const { load } = require('js-yaml')
const openapiDescription = load(fs.readFileSync('./Config/API.yaml'))

const testData = {
    "slides": [
        {
            "contents":
                [{ "component": {} }]
        }]
}

try {
    const ajv = new Ajv({ strict: false })
    addFormats(ajv)

    ajv.addSchema(openapiDescription, "API.yaml")

    let validate = ajv.validate({ "$ref": "API.yaml#/components/schemas/test" }, testData)


    console.log({
        valid: validate,
        error: ajv.errorsText(validate.errors)
    })
}
catch (error) {
    console.error(error.message)
}