Multiple fields with anyOf and self ref causes Maximum call stack size exceeded

[JJCella]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.28.0 (latest)

Plugin version

5.16.1 (latest)

Node.js version

20.11.0 (LTS)

Operating system

macOS Sonoma 14.5

Description

When defining a schema with at least two anyOf fields or oneOf fields with self ref like so :

import fastJson from 'fast-json-stringify';

const schema = {
  $schema: 'http://json-schema.org/draft-07/schema#',
  type: 'object',
  properties: {
    field: { type: 'string' },
    field1: { anyOf: [{ $ref: '#' }, { type: 'null' }] },
    field2: { anyOf: [{ $ref: '#' }, { type: 'null' }] },
  },
};

fastJson(schema.valueOf());

I'm getting this following error :

    RangeError: Maximum call stack size exceeded

      at RefResolver.#addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:143:14)
      at RefResolver.#addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:165:24)
      at RefResolver.#addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:165:24)
      at RefResolver.#addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:165:24)
      at RefResolver.#addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:165:24)
      at RefResolver.addSchema (../../node_modules/.pnpm/json-schema-ref-resolver@1.0.1/node_modules/json-schema-ref-resolver/index.js:30:20)
      at mergeLocations (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:433:23)
      at buildOneOf (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:868:24)
      at buildValue (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:979:12)
      at buildInnerObject (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:380:11)
      at buildObject (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:501:9)
      at buildSingleTypeSerializer (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:768:24)
      at buildValue (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:1010:13)
      at buildOneOf (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:874:26)
      at buildValue (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify/index.js:979:12)
      at buildInnerObject (../../node_modules/.pnpm/fast-json-stringify@5.16.1/node_modules/fast-json-stringify

(output truncated for readability)

Fastify fails to start when using this schema in routes

Is this kind of schema possible ? in my case, anyOf / oneOf + self reference & null are required.

[mcollina]

Currently this schema is not supported. However it would be cool if it was.
I'm not sure how hard it would be, but if you are willing to give it a shot it would be amazing.