Resperr is a Go package to associate status codes and messages with errors.
See blog post for a full description or read the test code for more context:
// write a simple handler that just checks for errors
// and replies with an error object if it gets one
func myHandler(w http.ResponseWriter, r *http.Request) {
// ... check user permissions...
if err := hasPermissions(r); err != nil {
replyError(w, r, err)
return
}
// ...validate request...
n, err := getItemNoFromRequest(r)
if err != nil {
replyError(w, r, err)
return
}
// ...get the data ...
item, err := getItemByNumber(n)
if err != nil {
replyError(w, r, err)
return
}
replyJSON(w, r, http.StatusOK, item)
}
// in the functions that your handler calls
// use resp err to associate different error conditions
// with appropriate HTTP status codes
func getItemByNumber(n int) (item *Item, err error) {
item, err = dbCall("...", n)
if err == sql.ErrNoRows {
// this is an anticipated 404
return nil, resperr.New(
http.StatusNotFound,
"%d not found", n)
}
if err != nil {
// this is an unexpected 500!
return nil, err
}
// ...
return
}
// you can also return specific messages for users as needed
func getItemNoFromRequest(r *http.Request) (int, error) {
ns := r.URL.Query().Get("n")
if ns == "" {
return 0, resperr.WithUserMessage(
resperr.New(
http.StatusBadRequest,
"missing ?n= in query"),
"Please enter a number.")
}
n, err := strconv.Atoi(ns)
if err != nil {
return 0, resperr.WithCodeAndMessage(
err, http.StatusBadRequest,
"Input is not a number.")
}
return n, nil
}
func hasPermissions(r *http.Request) error {
// lol, don't do this!
user := r.URL.Query().Get("user")
if user == "admin" {
return nil
}
return resperr.New(http.StatusForbidden,
"bad user %q", user)
}