Why all headers values are split as they are comma separated in EventToRequest?

[arabello]

I had an issue while integrating a custom header containing a comma , caused by RequestAccessorV2.EventToRequestWithContext: the request returned has the custom header value as an array of two strings (original value split into two parts) instead of an array of a single element (the entire value with the comma).

Looking at the code, it seems that the RequestAccessor splits headers values treating them as they all are comma-separated.

for headerKey, headerValue := range req.Headers {
    for _, val := range strings.Split(headerValue, ",") {
        httpRequest.Header.Add(headerKey, strings.Trim(val, " "))
    }
}

Why so? If an header is not defined as comma-separated no splitting strategy should occur, shouldn't it? What am I missing?

Moreover, why this behavior differs from the RequestAccessor (V1)?

[advdv]

We're running into this issue as well. In our case it is the Access-Control-Request-Headers, it is split before it reaches the CORS middleware: https://github.com/rs/cors/blob/1562b1715b353146f279ff7d445b7412e0f1a842/cors.go#L367. The middleware expects it to not be a multi-value and only looks the first element.