Function errorFromResponse

internal/barista/observability/telemetry.twirp.go:748–786

errorFromResponse builds a twirp.Error from a non-200 HTTP response. If the response has a valid serialized Twirp error, then it's returned. If not, the response status code is used to generate a similar twirp error. See twirpErrorFromIntermediary for more info on intermediary errors.

(resp *http.Response)

// If not, the response status code is used to generate a similar twirp
// error. See twirpErrorFromIntermediary for more info on intermediary errors.
func errorFromResponse(resp *http.Response) twirp.Error {
	statusCode := resp.StatusCode
	statusText := http.StatusText(statusCode)

	if isHTTPRedirect(statusCode) {
		// Unexpected redirect: it must be an error from an intermediary.
		// Twirp clients don't follow redirects automatically, Twirp only handles
		// POST requests, redirects should only happen on GET and HEAD requests.
		location := resp.Header.Get("Location")
		msg := fmt.Sprintf("unexpected HTTP status code %d %q received, Location=%q", statusCode, statusText, location)
		return twirpErrorFromIntermediary(statusCode, msg, location)
	}

	respBodyBytes, err := io.ReadAll(resp.Body)
	if err != nil {
		return wrapInternal(err, "failed to read server error response body")
	}

	var tj twerrJSON
	dec := json.NewDecoder(bytes.NewReader(respBodyBytes))
	dec.DisallowUnknownFields()
	if err := dec.Decode(&tj); err != nil || tj.Code == "" {
		// Invalid JSON response; it must be an error from an intermediary.
		msg := fmt.Sprintf("Error from intermediary with HTTP status code %d %q", statusCode, statusText)
		return twirpErrorFromIntermediary(statusCode, msg, string(respBodyBytes))
	}

	errorCode := twirp.ErrorCode(tj.Code)
	if !twirp.IsValidErrorCode(errorCode) {
		msg := "invalid type returned from server error response: " + tj.Code
		return twirp.InternalError(msg).WithMeta("body", string(respBodyBytes))
	}

	twerr := twirp.NewError(errorCode, tj.Msg)
	for k, v := range tj.Meta {
		twerr = twerr.WithMeta(k, v)
	}
	return twerr
}

// twirpErrorFromIntermediary maps HTTP errors from non-twirp sources to twirp errors.
// The mapping is similar to gRPC: https://github.com/grpc/grpc/blob/master/doc/http-grpc-status-mapping.md.