string auto convert to number

[miniboxhaha]

Prerequisites

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

Fastify version

3.2.0

Plugin version

No response

Node.js version

18.0

Operating system

Windows

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

win10

Description

use fastify with TypeBoxTypeProvider,validate will auto cast sting to number,and auto cast sting to string[]

for example code blow:

Steps to Reproduce

//server.ts
const server = fastify().withTypeProvider<TypeBoxTypeProvider>()
fastify.post<
            { Body: User[] }
        >('/marks', { schema: { body: properties} }, async (request, reply) => {
            try {
                reply.code(200).send()
            } catch (err) {
                reply.code(400).send(err)
            }
        }),

//validate.ts
export const properties = Type.Object({
   timestamp: Type.Readonly(Type.Integer()),
   users:Type.Optional(Type.Array(Type.String()))
})



//testData1:
{
   timestamp:1683687611279,
   users:["tom","jerry"]
}
expect:OK
result:OK

//testData2:
{
   timestamp:"1683687611279",
   users:"tom"
}
expect:False
result:OK

Expected Behavior

No response

[mcollina]

This is expected because Fastify creates Ajv with coerceTypes: "array" by default: https://www.fastify.io/docs/latest/Reference/Validation-and-Serialization/#schema-validator.

[miniboxhaha]

thanks，i will follow the doc