Define different sort order based on nested objects

In the current implementation, you can’t define different sort order based on nested objects

imagine I want a to be before b in root element and b to be before a under x element, as far as I can see, is not possible.

I’ve already created a solution for this on my local branch and would love to push it.

There are 3 options here that I see:

1. Adjust the arguments to be nested - sort key will be called with the key with nested name

test('Dumper should provide nested keys', function () {
  var nested = { a: 1, b: 2, x: { a: 2, b: 1 } };
  var expected = 'a: 1\nb: 2\nx:\n  b: 1\n  a: 2\n';
  var order = [ 'a', 'b', 'x', 'x.b', 'x.a' ];
  assert.deepEqual(yaml.safeDump(nested, {
    sortKeys: function (a, b) {
      return order.indexOf(a) - order.indexOf(b);
    }
  }), expected);

• Pro: Nice clean and friendly API
• Con: Break backward compatibility

1. Ad a third argument to sortKey - namespace (array)

test('Dumper should provide nested keys', function () {
  var nested = { a: 1, b: 2, x: { a: 2, b: 1 } };
  var expected = 'a: 1\nb: 2\nx:\n  b: 1\n  a: 2\n';
  var rootOrder = [ 'a', 'b', 'x' ];
  var xOrder = [ 'b', 'a' ];
  assert.deepEqual(yaml.safeDump(nested, {
    sortKeys: function (a, b, namespace) {
      if (namespace && namespace.length === 1 && namespace[0] === 'x') { // an ugly way to check if namespace === ['x']
        return xOrder.indexOf(a) - xOrder.indexOf(b);
      }
      return rootOrder.indexOf(a) - rootOrder.indexOf(b);
    }
  }), expected);

• Pro: backward compatible, doesn’t add ‘.’ as a special character
• Con: a sort function with a third parameter - yack!

1. Do not fix ( I’ll fork and use my own implementation)

I think you should go with option 2, it has an API flaw but it

_Originally posted by @ekeren in https://github.com/nodeca/js-yaml/pull/188/comment#issuecomment-434783584_

[puzrin]

I also remembered that sorting was guaranteed, but it turns out it is an implementation detail, not a language definition. Thus not guaranteed (as you can see in the above pdf)

I don’t like to make changes “just for fun”. It ordered objects work everywhere, why should we change anything?

[puzrin]

I’d prefer to close.