Cannot find reference with allOf

[remidewitte]

Prerequisites

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

Fastify version

4.5.3

Plugin version

5.3.0

Node.js version

16

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

12.2

Description

I suspect it comes from fastify/fastify#4049 shipped with fastify 4.2.0 but I cannot figure what is wrong with my case.
It used to work with fastify 4.1.0 .

Maybe you have a clue.

Steps to Reproduce

Schema is :

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "Test",
  "definitions": {
    "Problem": {
      "type": "object",
      "required": [
        "type"
      ],
      "additionalProperties": true,
      "properties": {
        "type": {
          "type": "string"
        }
      }
    },
    "ValidationFragment": {
      "type": "string"
    },
    "ValidationErrorProblem": {
      "type": "object",
      "allOf": [
        {
          "$ref": "#/definitions/Problem"
        },
        {
          "type": "object",
          "properties": {
            "validation": {
              "$ref": "#/definitions/ValidationFragment"
            }
          }
        }
      ]
    }
  },
  "additionalProperties": false,
  "type": "object"
}

Code is

import fastify from 'fastify';

const server = fastify();

const schema = require('./schema.json');
server.addSchema(schema);

server.post<{
}>(
  '/dummy',
  {
    schema: {
      response: {
        '400': {$ref: 'Test#/definitions/ValidationErrorProblem'},
      },
    }
  },
  async (_request, _reply) => {
    return 'OK'
  });

server.ready();

Error is :

node_modules/fastify/lib/route.js:326
              throw new FST_ERR_SCH_SERIALIZATION_BUILD(opts.method, url, error.message)
                    ^
FastifyError [Error]: Failed building the serialization schema for POST: /dummy, due to error Cannot find reference "#/definitions/ValidationFragment"

Expected Behavior

It used to work with fastify 4.1.0. I would expect FJS to compile the schema.

[climba03003]

The problem exist because of how allOf schema merged.

fast-json-stringify/index.js

Lines 385 to 484 in 68f7b69

	function mergeAllOfSchema (location, schema, mergedSchema) {
	const allOfLocation = mergeLocation(location, 'allOf')
	for (let i = 0; i < schema.allOf.length; i++) {
	let allOfSchema = schema.allOf[i]
	if (allOfSchema.$ref) {
	const allOfSchemaLocation = mergeLocation(allOfLocation, i)
	allOfSchema = resolveRef(allOfSchemaLocation, allOfSchema.$ref).schema
	}
	let allOfSchemaType = allOfSchema.type
	if (allOfSchemaType === undefined) {
	allOfSchemaType = inferTypeByKeyword(allOfSchema)
	}
	if (allOfSchemaType !== undefined) {
	if (
	mergedSchema.type !== undefined &&
	mergedSchema.type !== allOfSchemaType
	) {
	throw new Error('allOf schemas have different type values')
	}
	mergedSchema.type = allOfSchemaType
	}
	if (allOfSchema.format !== undefined) {
	if (
	mergedSchema.format !== undefined &&
	mergedSchema.format !== allOfSchema.format
	) {
	throw new Error('allOf schemas have different format values')
	}
	mergedSchema.format = allOfSchema.format
	}
	if (allOfSchema.nullable !== undefined) {
	if (
	mergedSchema.nullable !== undefined &&
	mergedSchema.nullable !== allOfSchema.nullable
	) {
	throw new Error('allOf schemas have different nullable values')
	}
	mergedSchema.nullable = allOfSchema.nullable
	}
	if (allOfSchema.properties !== undefined) {
	if (mergedSchema.properties === undefined) {
	mergedSchema.properties = {}
	}
	Object.assign(mergedSchema.properties, allOfSchema.properties)
	}
	if (allOfSchema.additionalProperties !== undefined) {
	if (mergedSchema.additionalProperties === undefined) {
	mergedSchema.additionalProperties = {}
	}
	Object.assign(mergedSchema.additionalProperties, allOfSchema.additionalProperties)
	}
	if (allOfSchema.patternProperties !== undefined) {
	if (mergedSchema.patternProperties === undefined) {
	mergedSchema.patternProperties = {}
	}
	Object.assign(mergedSchema.patternProperties, allOfSchema.patternProperties)
	}
	if (allOfSchema.required !== undefined) {
	if (mergedSchema.required === undefined) {
	mergedSchema.required = []
	}
	mergedSchema.required.push(...allOfSchema.required)
	}
	if (allOfSchema.oneOf !== undefined) {
	if (mergedSchema.oneOf === undefined) {
	mergedSchema.oneOf = []
	}
	mergedSchema.oneOf.push(...allOfSchema.oneOf)
	}
	if (allOfSchema.anyOf !== undefined) {
	if (mergedSchema.anyOf === undefined) {
	mergedSchema.anyOf = []
	}
	mergedSchema.anyOf.push(...allOfSchema.anyOf)
	}
	if (allOfSchema.allOf !== undefined) {
	mergeAllOfSchema(location, allOfSchema, mergedSchema)
	}
	}
	delete mergedSchema.allOf
	mergedSchema.$id = `merged_${randomUUID()}`
	mergeAllOfSchemas[mergedSchema.$id] = mergedSchema
	refResolver.addSchema(mergedSchema)
	location.schemaId = mergedSchema.$id
	location.jsonPointer = '#'
	}

I don't think it can be fixed in a short time, the problem here lead to a complicated use-case.
And it may even leads to a deep / infinite loop since it requires to find every reference inside the schema.

cc @ivan-tymoshenko Do you have a time to investigate this issue?

[climba03003]

As a workaround, I suggest you to change the schema as follow.

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "Test",
  "definitions": {
    "Problem": {
      "type": "object",
      "required": [
        "type"
      ],
      "additionalProperties": true,
      "properties": {
        "type": {
          "type": "string"
        }
      }
    },
    "ValidationFragment": {
      "type": "string"
    },
    "ValidationErrorProblem": {
      "type": "object",
      "allOf": [
        {
          "$ref": "#/definitions/Problem"
        },
        {
          "type": "object",
          "properties": {
            "validation": {
              // all nested schema reference by $id
              "$ref": "Test#/definitions/ValidationFragment"
            }
          }
        }
      ]
    }
  },
  "additionalProperties": false,
  "type": "object"
}

[remidewitte]

Thanks a lot for your quick answer and the workaround !
Let me know how I can help further.