Godot: parse_json: Document that JSON does not preserve order like Godot's dicts

[AlexHolly]

Godot Master

extends Node


func _ready():
    var dict = parse_json('{"D":1,"C":2,"B":3,"A":4}')
    print(dict)

# Output : (A:4), (B:3), (C:2), (D:1)

[vybr]

Tested it with a few more letters, it seems to put the keys in alphabetical order.

[vnen]

Technically JSON has no obligation to keep the key order.

[connorjclark]

JSON, nor dictionaries, are designed to preserve ordering.

[AlexHolly]

But Godot 3.0 Dictionaries do preserve order, so I was expecting it in this case too.

[connorjclark]

Oh, I didn't realize that. Still learning GDScript.

Seems the order is reversed. Solution may be as simple as changing a stack to a queue (etc.), which shouldn't have any perf. implications.

But, I would argue that you shouldn't design any application to rely on JSON key ordering.

[AlexHolly]

But, I would argue that you shouldn't design any application to rely on JSON key ordering.

I agree.

Maybe we can add a note to the docs?

[mhilbrunner]

As explained by others above, JSON objects don't guarantee any order for their keys.

From RFC 7159, the JSON spec:

An object is an unordered collection
An array is an ordered sequence

Indeed, it works fine for arrays: parse_json('[1,2,3]') corretly yields [1, 2, 3].

So the only remaining thing is that if someone is familiar with Godot dicts, but unfamiliar with JSON objects, they might not expect this to happen. Will add a note to the docs.