Every Fern API has a special file called
api.yml, which includes all the API-wide configuration.
fern/ ├─ fern.config.json └─ api/ ├─ generators.yml └─ definition/ ├─ api.yml # <--- └─ imdb.yml
This name is used to uniquely identify your API in your organization. If you
just have one API, then
api is a sufficient name.
You can define top level API docs. These docs will come through in the OpenAPI spec and Postman Collection.
name: api docs: | ## Header This API provides access to...
You can specify the authentication scheme used by your API.
Out of the box, Fern supports
Basic authentication schemes.
name: api auth: bearer
name: api auth: basic
You can also create your own authentication schemes.
name: api auth: MyAuthScheme auth-schemes: MyAuthScheme: header: X-API-Key type: string
You can specify headers that are meant to be included on every request:
name: api headers: X-App-Id: string
You can specify the environments where your backend is deployed. These are useful in most generated outputs, like SDKs and in Postman Collections.
name: api environments: Production: https://www.yoursite.com Staging: docs: This staging environment is helpful for testing! url: https://www.staging.yoursite.com
You can also provide a default environment:
name: api environments: Production: https://www.yoursite.com Staging: docs: This staging environment is helpful for testing! url: https://www.staging.yoursite.com default-environment: Production
Multiple URLs per environment
You can specify multiple URLs per environment. This is helpful if you have a microservice architecture, and you want a single SDK to interact with multiple servers.
environments: Production: urls: Auth: https://auth.yoursite.com Plants: https://plants.yoursite.com Staging: urls: Auth: https://auth.staging.yoursite.com Plants: https://plants.staging.yoursite.com
If you choose to use this feature, you must specify a
url for each service you define:
service: url: Auth base-path: /auth ...
Error discrimination strategy
In order to generate SDKs idiomatically, Fern needs to know how to differentiate between different errors when parsing an endpoint response.
Discriminate by status code
You can specify Fern to discriminate by status code. This means on each endpoint, every error that’s listed must have a different HTTP status code.
name: api error-discrimination: strategy: status-code
Discriminate by error name
You can specify Fern to discriminate by error name. If you select this strategy, then Fern will assume that every error response has an extra property denoting the error name.
If you use Fern to generate server-side boilerplate, then this option provides the most flexibility. Otherwise, you’ll probably want to use the status code discrimination strategy.
name: api error-discrimination: strategy: property property-name: errorName
You can import and list errors that will be thrown by every endpoint.
imports: commons: commons.yml errors: - commons.NotFoundError - commons.BadRequestError