fastify-swagger VS fastify-cli

With Speakeasy, you can create client SDKs based on an OpenAPI specification. Fastify ships with the @fastify/swagger plugin, which provides convenient shortcuts for generating good OpenAPI specifications. We'll start this tutorial by registering @fastify/swagger in a Fastify project to generate a spec.

First let’s get our current OpenAPI specification out of Fastify and onto the file system. If you have not added the https://github.com/fastify/fastify-swagger plugin first go do that. Then use this simple script I called generate-spec.ts to write your OpenAPI specification to the filesystem.

The fastify-swagger docs has an example https://github.com/fastify/fastify-swagger

@fastify/swagger is a fastify plugin to serve a Swagger UI, using Swagger (OpenAPI v2) or OpenAPI v3 schemas automatically generated from your route schemas, or from an existing Swagger/OpenAPI schema.

On the Node.js framework side of things, Fastify has support for Swagger with the fastify-swagger plugin.

With this approach, backend can be any programming languages that support OpenAPI or Swagger. Personally, I use fastify-swagger; but I can also be things like Python's FastAPI or Golang's Gin/Buffalo/Native.

You'll need Node.js installed (we used Node v20.5.1), and you'll need to install the Fastify CLI.

Fastify allows all that but if you start from scratch you may not perceive the difference from Express. That's why we recommend you to start your application with the CLI. It will not only bootstrap you application but will configure it to have TypeScript if you want.