docs: advice about @fastify/swagger version support in the README.md

[RodrigoDornelles]

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

2.1.0

Node.js version

20.1

Operating system

Linux

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

Linux 8a34e6999b2a 5.15.0-91-generic #101-Ubuntu SMP Tue Nov 14 13:30:08 UTC 2023 x86_64 Linux

Description

FastifyError [Error]: The decorator 'swaggerCSP' has already been added!
    at decorate (/app/node_modules/fastify/lib/decorate.js:23:11)
    at Object.decorateFastify [as decorate] (/app/node_modules/fastify/lib/decorate.js:67:3)
    at fastifySwaggerUi (/app/node_modules/@fastify/swagger-ui/index.js:11:11) {
  code: 'FST_ERR_DEC_ALREADY_PRESENT',
  statusCode: 500
}

Steps to Reproduce

import fastify from 'fastify';
import fastifySwagger from '@fastify/swagger';
import fastifySwaggerUI from '@fastify/swagger-ui';

const app = fastify();

app.register(fastifySwagger)
app.register(fastifySwaggerUI, {
  routePrefix: '/docs',
});

app.get('/', async (request, reply) => {
  return { hello: 'world!' };
});

app.ready()

Expected Behavior

work without errors

[Uzlopak]

Maybe you use an old @fastify/swagger version. Can you provide a repo with an example project please?

[RodrigoDornelles]

That's right, it works with version 8 and there is a problem with version 7!

@Uzlopak a suggestion before closing my issue would be a friendly error message, if the lifecycle allows it.

[Uzlopak]

That error message comes from fastify core. Maybe the solution is to write that we this plugin needs atleast fastify swagger v. x

[RodrigoDornelles]

That error message comes from fastify core. Maybe the solution is to write that we this plugin needs atleast fastify swagger v. x

advice in the repository's README.md is perfect!

[Uzlopak]

Reopening as we did not solve this documentation issue, yet ;)