Swagger multiple document not working when use Nestjs Fastify

[JackoPham]

When I try to working Swagger multiple document with the nestjs + fastify , I had got error as below. Please kindly help me resolve it.

In the case use one document, it's work. It's not working when I add more than 1 document.

I use with versions.

    "@nestjs/common": "^6.1.1",
    "@nestjs/core": "^6.1.1",
    "@nestjs/graphql": "^6.0.5",
    "@nestjs/platform-fastify": "^6.1.1",
    "@nestjs/platform-socket.io": "^6.1.1",
    "@nestjs/swagger": "^3.0.2",
    "@nestjs/typeorm": "^6.0.0",

import {
  FastifyAdapter,
  NestFastifyApplication,
} from '@nestjs/platform-fastify';

const serverApp = new FastifyAdapter();
  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    serverApp
  );
  const options = new DocumentBuilder()
    .setTitle('Cats example')
    .setDescription('The cats API description')
    .setVersion('1.0')
    .addTag('cats')
    .build();

  const catDocument = SwaggerModule.createDocument(app, options, {
    include: [SystemModule],
  });
  SwaggerModule.setup('docs/cat', app, catDocument);

  const secondOptions = new DocumentBuilder()
    .setTitle('Dogs example')
    .setDescription('The dogs API description')
    .setVersion('1.0')
    .addTag('dogs')
    .build();

  const dogDocument = SwaggerModule.createDocument(app, secondOptions, {
    include: [UserModule],
  });
  SwaggerModule.setup('api/dogs', app, dogDocument);

  await app.listen(port);

======> With error.
/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/@nestjs/platform-fastify/node_modules/fastify/lib/decorate.js:17
    throw new FST_ERR_DEC_ALREADY_PRESENT(name)
    ^
FastifyError [FST_ERR_DEC_ALREADY_PRESENT]: FST_ERR_DEC_ALREADY_PRESENT: The decorator 'swagger' has already been added!
    at decorate (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/@nestjs/platform-fastify/node_modules/fastify/lib/decorate.js:17:11)
    at Object.decorateFastify [as decorate] (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/@nestjs/platform-fastify/node_modules/fastify/lib/decorate.js:35:3)
    at Object.module.exports [as static] (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/fastify-swagger/static.js:59:11)
    at fastifySwagger (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/fastify-swagger/index.js:15:19)
    at Plugin.exec (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/avvio/plugin.js:89:17)
    at Boot.loadPlugin (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/avvio/plugin.js:175:10)
    at Task.release (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/fastq/queue.js:127:16)
    at worked (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/fastq/queue.js:169:10)
    at toLoad.finish (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/avvio/plugin.js:178:7)
    at done (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/avvio/plugin.js:136:5)
    at check (/mnt/d/PROJECTS/PRIVATE/nestjs-fastify/node_modules/avvio/plugin.js:147:7)
    at process._tickCallback (internal/process/next_tick.js:61:11)

[nartc]

swagger/lib/swagger-module.ts

Line 71 in 9bdad6c

httpServer.register(loadPackage('fastify-swagger', 'SwaggerModule'), {

https://github.com/fastify/fastify-swagger/blob/c41d37cd4a2ceb6b1a667f3dd03f8ccf5f53e2bf/static.js#L59

I don't think there's anything we can do right now. Under the hood, fastify-swagger calls fastify.decorate('swagger',...) to register this swagger decorator so you can only have one document with Fastify as of the moment :)

Try raising this issue to fastify-swagger repo?

[JackoPham]

swagger/lib/swagger-module.ts

Line 71 in 9bdad6c

httpServer.register(loadPackage('fastify-swagger', 'SwaggerModule'), {
https://github.com/fastify/fastify-swagger/blob/c41d37cd4a2ceb6b1a667f3dd03f8ccf5f53e2bf/static.js#L59

I don't think there's anything we can do right now. Under the hood, fastify-swagger calls fastify.decorate('swagger',...) to register this swagger decorator so you can only have one document with Fastify as of the moment :)

Try raising this issue to fastify-swagger repo?

Thank you for your quick answer. When I working with nest + express, It's ok. But when I change to Fastify I encountered this error and I think that was the cause of Nestjs.

[nartc]

No it’s not the cause of Nest. We use two different wrappers for Express (swagger-ui-express) and Fastify (fastify-swagger). Fastify Swagger sets up the decorator with a hardcoded “swagger” string under the hood, that prevents multiple swaggers to be registered with Fastify.

[lock]

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