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SkiFire13 • yesterday at 9:22 PM • 2 replies • view on HN

> nil slices and maps are marshaled as an empty JSON array or object by default

I feel that is the kind of broken default that will come back and bite a bunch of people, and will eventually need to be fixed in a v3.

Replies

travisd • yesterday at 9:30 PM

I think it'll bite some people, but probably is the better default for JSON specifically. Most of the nil-maps-become-null thing is just an extension of Go defaulting to nil for empty arrays and maps, which is usually not what you expect when you're writing a JSON schema like

    type ListUsersResponse struct {
        Users []User `json:"users"`
    }
in Go. It's pretty common have code like

    userRows := db.Query(...)
    var users []api.User
    for _, user := range userRows {
        users = append(users, api.User{...})
    }
where you don't _really_ intend for the default nil-ness to leak out. (Apologies for any broken syntax, I'm realizing in real time that it's been a while since I've written Go)
devmor • yesterday at 9:24 PM

Can you explain why? This seems like the appropriate expectation to me, given how JSON is constructed and consumed.