I have extended Sale Order Line with parent / child hierarchy relationship because some lines (children) can be connected to others (parent) in the same Sale Order

class SaleOrderLine(models.Model):
  _inherit = 'sale.order.line'
  _parent_name = 'my_parent_id'

  my_parent_id = fields.Many2one('sale.order.line', 'Operation for', index=True, domain='[("my_parent_id", "=", False)]', ondelete='cascade')

  my_children_ids = fields.One2many('sale.order.line', 'my_parent_id', 'Operations')

I am presenting children records differently in the view (different row color, disabled re-sequennce, and so on) based on the `my_parent_id` field (and I am also dealing with re-sequencing of the children together with the parent and all the rest) which is working fine

The problem I have is that I don't know how to properly add a new parent line with couple of children records on changing some field of an existing line (in the same Sale Order)

Meaning that if I change the quantity of one line, based on some conditions of course, I need to add another parent line with couple of children lines.

There are actually two problems, combined (examples of code below):

1. Where exactly to put the code ?

   1. Most logical place would be in `sale_order_line.onchange('product_uom_qty')`
      But here I couldn't add even the single parent line using `self.new()` (it's just not showing up) although I'm on the same model, and using `self.create()` it's working but the new records do not show up until the user saves the Sale Order or just refresh / reloads it (as the records have been created into the DB using create() method)

   2. I did try also on `sale_order.onchange('order_line')`
      Here it's working to add the lines even with `new()` but the problem is that the parent / child relationship it's not held

2. What method to use ?

   1. `sale_order_line.new()` - I would have preferred not to have the records saved into DB directly (in order to allow user to discard the change) but at least one method to work would be nice ... but this is not keeping the parent / child relationship
      Although if using debugger on the moment they're added, the connection between them seems fine using the NewIDs but as soon as the transaction finishes (I don't know which other code it's executing after my function) the relation drops (on next debug the relationship fields are empty)
      

   2. `sale_order_line.create()` - this seems to work, adding first the parent line and then connecting each child with the parent record ID, but the records do not show up in the view until user saves the Sale Order or simply refreshes / reloads the page

   3. `sale_order.update({'order_line': [(0, 0, {'product_id': parent, 'my_children_ids': [(0, 0, child products ...)]})` same issues as above
      

Code examples:

1. using `sale_order_line.new()` inside `sale_order_line._onchange_product_uom_qty()` method

not working at all, even for the single parent line, it doesn't show up ...

# in my SaleOrderLine extension class
@api.onchange('product_uom_qty')
def _onchange_product_uom_qty(self):
  new_parent_line = self.new({
    'order_id': rec.order_id.id,
    'product_id': 10,
    # I'm adding all the other required fields just to be sure ...
    'name': 'Test parent',
    'price_unit': 10,
    'product_uom_qty': 1,
  })

2. using `sale_order_line.create()` inside `sale_order_line._onchange_product_uom_qty()` method

it's working, even adding child lines correctly, but:

•  they are not visible to the user until Sale Order get's saved manually by the user (which does some kind of refresh afterwards) or entire page reloaded (as the records are already saved in the DB)
  Is there a method to save the Sale Order from code and automatically show the new records created ?
  

• it would have been nice to be able to use the discard functionality (like new()) - but anyway, at least one decent way to achieve what I need would be nice though (correct parent / child relationship and displayed to the user after the change ...)
  

# in my SaleOrderLine extension class
@api.onchange('product_uom_qty')
def _onchange_product_uom_qty(self):
  new_parent_line = self.create({
    # I need to use the _origin to take order integer ID instead of the NewID format in order to work correctly ...
    'order_id': rec._origin.order_id.id,
    'product_id': 10,
    # I'm adding all the other required fields just to be sure ...
    'name': 'Test parent',
    'price_unit': 10,
    'product_uom_qty': 1,
    # this doesn't work to automatically create children records too ...
    # 'my_children_ids': [
    # (0, 0, {child 1 values ...}),
    # (0, 0, {child 2 values ...}),
    # ],
  })

  new_child_1_line = self.create({
    'my_parent_id': new_parent_line.id,
     # other child 1 values ...
  })

3. using `sale_order.order_line.new()` from `sale_order._onchange_order_line()`

The records show up, but the parent / child relation it's not kept

Actually debugging the code during execution which adds them, the relationship seems fine (based on the NewIDs), but as soon as the code ends (and whatever the framework does afterwards) it seems that is broken

I've debugged again and for those records the link fields (parent / child) are empty

# in my SaleOrder extension class
@api.onchange('order_line')
def _onchange_order_line(self):
  new_parent_line = self.order_line.new({
    'order_id': self.id,
    'product_id': 10,
    # I'm adding all the other required fields just to be sure ...
    'name': 'Test parent',
    'price_unit': 10,
    'product_uom_qty': 1,
    'my_children_ids': [
      (0, 0, {child 1 values ...}),
      (0, 0, {child 2 values ...}),
    ]
  })

4. using `sale_order.update({'order_line': [(0, 0, {parent values ...}]})` from `sale_order._omchange_order_line()`

the same like point above, they appear but without parent / child relation

# in my SaleOrder extension class
@api.onchange('order_line')
def _onchange_order_line(self):
  self.update({
    'order_line': [(0, 0, {
      'order_id': self.id,
      'product_id': 10,
      # I'm adding all the other required fields just to be sure ...
      'name': 'Test parent',
      'price_unit': 10,
      'product_uom_qty': 1,
      'my_children_ids': [
        (0, 0, {child 1 values ...}),
        (0, 0, {child 2 values ...}),
      ]
    })]
  })

Are there any other ways to achieve what I need ?

Thx,