In Odoo, the behavior you described is by design. Odoo's Purchase Order (PO) and Goods Receipt (GR) processes are deliberately separate to ensure a clear audit trail between the purchase agreement (PO) and what is actually received. However, this can be modified if you want to update the Purchase Order (PO) and Vendor Bill automatically when extra products are received.

Here’s how you can achieve it:

Solution 1: Automated Action

You can use Odoo's Automated Actions to automatically update the Purchase Order based on extra products received in the receipt.

Steps:

1. Enable Developer Mode:
   • Go to Settings > Activate Developer Mode.
2. Create the Automated Action:
   • Go to Settings > Technical > Automated Actions.
   • Create a new Automated Action with the following configuration:
     • Model: Stock Picking
     • Trigger: On Creation & Update
     • Filter Domain: picking_type_id.code = 'incoming'
     • Action To Do: Execute Python Code.
3. Python Code for the Action: Add the following code to update the PO with extra received products:

   for move in record.move_ids_without_package:
       po_line = record.purchase_id.order_line.filtered(lambda l: l.product_id == move.product_id)
       if not po_line:
           record.purchase_id.order_line.create({
               'order_id': record.purchase_id.id,
               'product_id': move.product_id.id,
               'product_qty': move.product_uom_qty,
               'product_uom': move.product_uom.id,
               'price_unit': move.product_id.standard_price,  # Or use a custom logic for pricing
               'date_planned': record.scheduled_date or fields.Datetime.now(),
           })
   

   Explanation:
   • This code checks if the product received (move.product_id) is already in the Purchase Order line.
   • If not, it creates a new PO line with the details from the stock move.
4. Test the Automated Action:
   • Create a PO and validate a Goods Receipt with extra products using the barcode scanner.
   • Verify that the PO updates with the new products.

Solution 2: Customize the Behavior with a Custom Module

For more robust and maintainable functionality, creating a custom module is recommended. Below is an outline of how this could be implemented.

Key Features:

• Detect extra products during receipt validation.
• Update the Purchase Order and Vendor Bill with the extra products.

Code Example:

from odoo import api, models

class StockPicking(models.Model):
    _inherit = 'stock.picking'

    @api.model
    def button_validate(self):
        res = super(StockPicking, self).button_validate()
        if self.picking_type_id.code == 'incoming' and self.purchase_id:
            for move in self.move_ids_without_package:
                po_line = self.purchase_id.order_line.filtered(lambda l: l.product_id == move.product_id)
                if not po_line:
                    self.purchase_id.order_line.create({
                        'order_id': self.purchase_id.id,
                        'product_id': move.product_id.id,
                        'product_qty': move.product_uom_qty,
                        'product_uom': move.product_uom.id,
                        'price_unit': move.product_id.standard_price,  # Or custom pricing
                        'date_planned': self.scheduled_date or fields.Datetime.now(),
                    })
        return res

Steps:

1. Create a custom Odoo module with the above logic.
2. Extend the button_validate method in stock.picking to trigger the PO update during Goods Receipt validation.
3. Install the module and test its behavior.

Solution 3: Manual Update Option

If you prefer to keep the process more controlled, you can create a custom button or wizard to review extra products received and update the Purchase Order manually.

Why It Doesn't Work Automatically for POs?

Odoo does not update POs automatically during Goods Receipts because:

• A Purchase Order is a legally binding agreement between the company and the vendor.
• Updating it dynamically may create inconsistencies in terms of traceability and accountability.
• Sales Orders allow updates since they are typically more dynamic and less tied to vendor agreements.

Conclusion

While Odoo doesn’t natively support this functionality for Purchase Orders, the above approaches can be used to automate or streamline the process. Using a custom module is the most reliable and scalable solution for this requirement. Let me know if you'd like help with the custom module code or configuration!