Type error when sending Readable to reply.send

[theguacamoleking]

Prerequisites

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

Fastify version

5

Plugin version

4.0.1

Node.js version

20

Operating system

Linux

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

n/a

Description

The following schema

{
  schema: {
    // ...
    response: {
      200: {
        type: 'string',
        headers: {
          'Content-Type': { type: 'application/octet-stream', default: 'text/csv' },
        },
      },
    },
  },
}

Leads to reply.send being typed as (payload: string | undefined) => ....

This is problematic because sending streams leads to a type error

Argument of type Readable is not assignable to parameter of type string.

Link to code that reproduces the bug

No response

Expected Behavior

reply.send(someReadable) does not lead to a type error