Required body with optional properties

[hpohlmeyer]

Prerequisites

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

🚀 Feature Proposal

I would like to have a way to mark a request bodies as required, even if the body only has optional properties.

Motivation

This is a follow-up to #541. While this solves part of my problem, it still does not reflect the defined schema.
The following example illustrates the problem (it uses typebox for schema generation):

// user.types.ts

export const updateUserBody = Type.Object({
  firstName: Type.Optional(Type.String()),
  lastName: Type.Optional(Type.String()),
})

export type UpdateUserRoute = {
  Body: Static<typeof updateUserBody>;
};

// user.routes.ts

export default (fastify) => {
  fastify.put<UpdateUserRoute>(
    "/user",
    { schema: { body: updateUserBody } },
    (request) => console.log(request.body.firstName)
  )
}

Because no property inside the body is required, fastify-swagger will not mark the request body as required.
In theory this would allow me to send a fetch request with an empty body:

const response = await fetch("http://localhost:300/user", {
  method: "put",
  headers: { "Content-Type": "application/json" },
};

console.log(await response.json()) // => [400] Body cannot be empty when content-type is set to 'application/json'

… but fastify always prevents this, because it is not valid JSON. You could argue, that this is not a problem, because you would never do something like this, but if you generate your frontend client with something like oazapfts, you will end up with a signature that has an optional body. And not sending a body will always result in a failed request.

Example

See above

[mcollina]

What is preventing you to mark the body as required?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.