This is a workaround for #1375 that allows working with SSE streams outside of the generated client code.

I'm not sure if it'd be appropriate to add an SSE implementation at this time, since there currently isn't an agreed upon standard for how to interpret OpenAPI schemas for text/event-stream responses and there's lots of different ways people are constructing them. I did think of providing a basic wrapper around the exposed http.Response that implements the SSE protocol and could be updated later to handle decoding event data, but there's already established libraries out there that can do the job (albeit most of them do expect to own the request and response, not just the response, so not as straight forward as it could be).

By adding x-ogen-raw-response: true to each text/event-stream response, this patch will cause ogen to expose the raw http.Response without first reading it's body, e.g.:

"text/event-stream": {
    "schema": {
        "items": {
            "$ref": "#/components/schemas/MyEvent"
        },
        "type": "array"
    },
    "x-ogen-raw-response": true
}

(this is just one example of how you might represent an SSE stream.)

This flag will also change server code-gen to give full control over the handler (I've separated these handlers into a new interface since the Client's methods don't match the handler signatures for raw requests).

One can also add an application/json response with the same schema to generate encoders/decoders for it (I'd recommend doing this in a patch script, which I find myself reaching for with most OpenAPI schemas I encounter anyways).

Now when we call our generated client method, we'll get something like this back:

type SuscribeToEventsOKRawTextEventStream struct {
	Response *http.Response `json:"-"`
}

Which we can then pass into our SSE reader of choice to stream the events.

This is most useful when also enabling request editing features:

generator:
  features:
    enable:
      - "paths/client"
      - "client/request/options"
      - "client/editors"

We'd pass an option to either our client construction or the request method that sets the appropriate headers, e.g.:

req.Header.Set("Cache-Control", "no-cache")
req.Header.Set("Accept", "text/event-stream")
req.Header.Set("Connection", "keep-alive")