Pattern for reading response in middleware?

[EliRibble]

I'm adding this for anyone who find this. I had originally searched the documentation about caveats related to middleware that reads the response content, and found nothing specific. I eventually read the code for the existing middleware. I originally had something like this:

func restyMiddleware(rclient *resty.Client, response *resty.Response) error {
        ctx := context.Background()
        buffer, err := io.ReadAll(response.Body)
        if err != nil {
                return fmt.Errorf("read body: %w", err)
        }
        response.Body.Close()
        response.Body = io.NopCloser(bytes.NewReader(buffer))
        var body types.JSON[json.RawMessage]

        err = body.UnmarshalJSON(buffer)
        if err != nil {
                return fmt.Errorf("unmarshal json: %w", err)
        }
        addToAggregator(body)
        return nil
}

In English, I want to be able to have middleware that can read the JSON body of the response for all actions on a client. I then use this data in an aggregator, which doesn't really matter here.

My issue was that if I read the response body I will end up with an error unmarshal json: unexpected end of JSON input later. The code that reads later is of the form:

var result GeocodeResponse
resp, err := s.client.R().
                SetQueryParamsFromValues(query).
                SetContext(ctx).
                SetResult(&result).
                SetPathParam("urlBase", s.urlBase).
                SetQueryParam("api_key", s.APIKey).
                Get("https://{urlBase}/geocoding/v2/autocomplete")

I found that my code above does not work. The solution is much simpler, and more elegant.

1. Enable unlimited response body reads.
2. Use convenience Bytes() helper.

Example:

func setup() {
  client := resty.New()
  client.SetResponseBodyUnlimitedReads(true)
  client.AddResponseMiddleware(restyMiddleware)
}

func restyMiddleware(rclient *resty.Client, response *resty.Response) error {
        ctx := context.Background()
        var body bobtypes.JSON[json.RawMessage]
        err := body.UnmarshalJSON(response.Bytes())
        if err != nil {
                return fmt.Errorf("unmarshal json in middleware: %w", err)
        }
        addToAggregator(body)
        return nil
}

Hopefully this saves someone the couple hours it cost me. Or an AI or something. Who knows anymore...

[jeevatkm]

Adding docs link reference: https://resty.dev/docs/unlimited-response-body-reads/