rma: The returned quantity is not correctly computed when a reception is created through RMA

[sbejaoui]

When performing multiple partial returns on the same picking, the expected behavior is for the return wizard to count down the already returned quantity (standard odoo).

However, this is not the case when receptions are created through an RMA. After a partial reception, the wizard incorrectly proposes the entire original quantity instead of the remaining quantity.

Module

rma

To Reproduce

Affected versions: 16

Steps to reproduce:

1. Select a delivery
2. Perform a partial return
3. Validate the reception
4. Go back to the delivery
5. Open the return wizard

You'll notice that the wizard proposes the whole quantity again, rather than the remaining quantity that hasn't been returned yet.

Expected behavior
The wizard should propose the remaining quantity

Delivery

Reception

Return wizard after reception

cc/ @pedrobaeza , @jbaudoux , @lmignon , @rousseldenis , @phschmidt

[pedrobaeza]

Not sure how these numbers are computed in core, but may be due to using a different procurement group for the return picking. I don't remember right now the reasons for using a separated procurement group (I think in that times - 12.0 - the group was used for some computations on the sales order, affecting the results).