goconst warnings from linter

Question

I'm using Atom to develop my Go app. The Linter in Atom is reporting an odd warning, and I don't see how it's a problem. Should I forever ignore the warning, or is there an alternate method I can implement?

Error: Warning goconst 3 other occurrence(s) of "GET" found in: routes_pages.go:384:8 routes_pages.go:443:7 routes_pages.go:536:7 (goconst) 198:8

Details:

I have routes in a file "app.go":

a.Router.HandleFunc("/login", a.PageLogin)
a.Router.HandleFunc("/register", a.PageRegister)
a.Router.HandleFunc("/event/add", a.PageEventCreate)

In a "routes_pages.go" file, I have func's defined like so:

func (a *App) PageEventCreate(w http.ResponseWriter, r *http.Request) {

    switch r.Method {
        case "GET":
            // Serve the resource.
        case "POST":
            // Create a new record.
        case "PUT":
            // Update an existing record.
        case "DELETE":
            // Remove the record.
        default:
            // Give an error message.
    }

}



func (a *App) PageLogin(res http.ResponseWriter, req *http.Request) {
        switch r.Method {
            case "GET":
                // Serve the resource.
            case "POST":
                // Create a new record.
            case "PUT":
                // Update an existing record.
            case "DELETE":
                // Remove the record.
            default:
                // Give an error message.
        }

}

I have a multitude of func's setup this way. It makes it easy to work on any case (GET, POST, etc) in one place.

The Linter in Atom has a problem with this. It's reporting a warning for each item, for example:

Warning goconst 3 other occurrence(s) of "GET" found in: routes_pages.go:384:8 routes_pages.go:443:7 routes_pages.go:536:7 (goconst)    198:8

This warning occurs many times; once for every instance of switch/case with GET, PUT, DELETE, etc; ultimately, for me it's a huge list (thus a huge error list).

I see no apparent way to 'ignore' the warning in Atom, so I feel like just disabling the linter, which is not great for more serious warnings...

Answer 1

It's just a warning that you're re-using the same string literal in multiple places. This can be problematic because string literals are liable to be misspelled without noticing. The solution is to use a constant instead. This is made very easy in your case, because all of the (standard) HTTP verbs are already constants exported by the http package. Just update your string literals to use the contant version instead:

func (a *App) PageLogin(res http.ResponseWriter, req *http.Request) {
        switch r.Method {
            case http.MethodGet:
                // Serve the resource.
            case http.MethodPost:
                // Create a new record.
            case http.MethodPut:
                // Update an existing record.
            case http.MethodDelete:
                // Remove the record.
            default:
                // Give an error message.
        }
}

By using a constant, you safeguard against an accidental typo. Example:

req, err := http.NewRequest("DLETE", ...)

would not result in a compile-time error (and may not even result in a runtime error, depending on the rest of your program's logic), but

req, err := http.NewRequest(http.MethodDlete, ...)

will fail to compile.