fastify-swagger VS openapi-diff

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.

Introducing our star player for detecting breaking changes: OpenAPI Diff. The good news? You can fire it up locally with Docker. Here’s how:

Now that we have a way to lookup our API’s behavior with Git, we can start testing for breaking changes between versions of our API. We’ll be using Optic (an open source tool I created) to do just that. If you are looking for other options I recommend https://github.com/OpenAPITools/openapi-diff or https://github.com/Tufin/oasdiff.

One option is to use OpenAPI to define the contracts. And then when you update the definitions, run something like https://github.com/OpenAPITools/openapi-diff to make sure there are no incompatibilities.