proposal: net/http: customizable Not Found and Method Not Allowed handlers #67971
Description
Proposal Details
With the HTTP router changes in go1.22, many developers are considering standard library for daily use or production. Although, as of now, NotFound and MethodNotAllowed handlers are hard coded, with no way of change or overriding them.
If we look at thefindHandler function, we see:
//...
allowedMethods := mux.matchingMethods(host, path)
if len(allowedMethods) > 0 {
return HandlerFunc(func(w ResponseWriter, r *Request) {
w.Header().Set("Allow", strings.Join(allowedMethods, ", "))
Error(w, StatusText(StatusMethodNotAllowed), StatusMethodNotAllowed)
}), "", nil, nil
}
return NotFoundHandler(), "", nil, nil
//...I propose adding the option to set these two handlers.
Implementation
Referring to my PR (#67970), a new MuxOption type is introduced and two functions called WithNotFoundHandler and WithNotAllowedHandler are added.
Also, function NewServeMux is updated to accept variadic parameter of type MuxOption. This ensures backward compatibility, while allowing for customization.
To make sure the default value of ServeMux is valid as well, findHandler function is updated to use custom handlers if provided, or to use the default handlers otherwise.