Bad request for querystring when using explode is false

[mstimvol]

Prerequisites

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

Fastify version

4.25.2

Plugin version

8.14.0

Node.js version

18.12.1

Operating system

Windows

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

Windows 11

Description

I've a get request that sends a comma separated list of ids to fastify. But when I send more than one id, I'm getting the following error:

{
    "statusCode": 400,
    "code": "FST_ERR_VALIDATION",
    "error": "Bad Request",
    "message": "querystring/ids/0 must be number"
}

That's the request that causes the error: GET http://localhost:8888/test?ids=201,202

Steps to Reproduce

  const fastify = Fastify({
    logger: true,

    ajv: {
      plugins: [
        function (ajv) {
          ajv.addKeyword({ keyword: 'style' })
          ajv.addKeyword({ keyword: 'explode' })
        }
      ]
    }
  })

  await fastify.register(FastifySwagger, {
    openapi: {
      info: {
        title: 'MyAPI',
        version: '0.1.0'
      },
      host: 'https://host.tld',
      schemes: ['http', 'https'],
      consumes: ['application/json'],
      produces: ['application/json']
    }
  })

  fastify.get('/test', {
    schema: {
      querystring: {
        type: 'object',
        additionalProperties: false,
        properties: {
          ids: {
            type: 'array',
            description: 'List of ids to return',
            uniqueItems: true,
            items: {
              type: 'number',
              format: 'int64',
              exclusiveMinimum: 200
            }
          },
          explode: false
        }
      }
    }
  }, (req) => {
    // do something
    console.log(req.query)
    return ''
  })

  await fastify.listen({
    host: 'localhost',
    port: 8888
  })

Expected Behavior

My expected behavior is that req.query.ids is an array that contains the ids, e.g. [201, 202, 203].

[Uzlopak]

Without deeper checking, i think you also need to set an appropriate querystring parser which can handle that format. The native querystring parser is afaik not able to handle that exploded format.