[Feature] Object Oriented SDKs

[dsinghvi]

Problem description

Often times, API resources are interconnected and it is natural to propagate these relationships directly into the SDK. See the snippet below, which uses the Github API as an example

const user = client.user.get("user-id..."); 
const repositories = user.get_repos(); 

In the example above, you can call get_repos directly on the user response. In comparison, today, with Fern, the user would instead have to call client.repositories.filter(user_id = user.id).

Why would it be useful?

This is more intuitive for developers and reduces boilerplate.

Describe the solution (optional)

The solution here is to introduce a new primitive into fern, called "methods". Every type defined in the API can have methods, which make calls to API endpoints. For the users example above, this is what the Fern Definition would look like:

imports: 
  repos: repos.yml

types: 
  User: 
    methods: # <---------------  new methods key
      get_repos: # <------------  name of method
        endpoint: repos.list # <--- the endpoint to proxy to 
        parameters: 
          user_id: $.id  # <-------- any parameters to pass in from the type itself
    properties: 
      id: 
        type: string
        docs: The ID of the user. 

For users coming from OpenAPI, we would support a x-fern-methods extension directly on the schema.

components: 
  schemas: 
    User: 
      x-fern-methods: 
        get_repos: 
           path: /users
           method: POST
           parameters: 
             user_id: $.id
      properties: 
        id:
          type: string