The goal of this lib is to play the onchange methods to get values for the fields not yet filled into the received list of values used to createor update a record. Therefore, the values from the user must be preserved. If we don't process on this way and you play the onchange methods on a sale.order for a new line with 'product_id' and 'product_uom_qty', the product_uom_qty will be reset to 1 when the onchange for product_id will be played and we'll lost the initial value for product_uom_qty
Before this change, the inmemory record was populated from values copied from the exisitng record.
It was no predictable to know in advance which values were required to correctly play onchange methods. Therefore all the values defined on the model were copied from the exising record to populate the inmemory record. The side effect of this approach was that in a lot of cases, a lot of useless values was copied leading to performance issue with computed fields.
With this change, we use the current record to call the onchange methods in an onchange context to avoid direct write to the database each time a new value is assigned by an onchange. At the end of the process, we restore the current record to its original state and return a dictionary with only the fields modified by the onchange.
Laurent Mignon (ACSONE)