[FIX] purchase: stop adding useless vendor to product vendor list

Current behavior:
When you create a contact and a delivery adress for this contact. If you
add the delivery adress as a vendor to a product, and purchase this
product from the delivery adress, the contact will be added to the
product vendor list.

Steps to reproduce:
- Create contact C
- Create delivery adress D for C
- Create product P
- Add D as a vendor to P
- Create PO for P from D, and confirm it
- Go to P, and check the vendor list (C is there)

opw-3177309

closes odoo/odoo#117902

X-original-commit: 67031d2b3d7d52297d18a69c76b4f747b17142e3
Signed-off-by: Engels Robin (roen) <roen@odoo.com>

addons/purchase/models/purchase.py

@@ -523,7 +523,8 @@ class PurchaseOrder(models.Model):
         for line in self.order_line:
             # Do not add a contact as a supplier
             partner = self.partner_id if not self.partner_id.parent_id else self.partner_id.parent_id
-            if line.product_id and partner not in line.product_id.seller_ids.partner_id and len(line.product_id.seller_ids) <= 10:
+            already_seller = (partner | self.partner_id) & line.product_id.seller_ids.mapped('partner_id')
+            if line.product_id and not already_seller and len(line.product_id.seller_ids) <= 10:
                 # Convert the price in the right currency.
                 currency = partner.property_purchase_currency_id or self.env.company.currency_id
                 price = self.currency_id._convert(line.price_unit, currency, line.company_id, line.date_order or fields.Date.today(), round=False)

addons/purchase/tests/test_purchase.py

@@ -333,3 +333,42 @@ class TestPurchase(AccountTestInvoicingCommon):
             po_line.product_id = product
         purchase_order_coco = po_form.save()
         self.assertEqual(purchase_order_coco.order_line.price_unit, currency_rate.rate * product.standard_price, "Value shouldn't be rounded 🍫")
+
+    def test_purchase_not_creating_useless_product_vendor(self):
+        """ This test ensures that the product vendor is not created when the
+        product is not set on the purchase order line.
+        """
+
+        #create a contact of type contact
+        contact = self.env['res.partner'].create({
+            'name': 'Contact',
+            'type': 'contact',
+        })
+
+        #create a contact of type Delivery Address lnked to the contact
+        delivery_address = self.env['res.partner'].create({
+            'name': 'Delivery Address',
+            'type': 'delivery',
+            'parent_id': contact.id,
+        })
+
+        #create a product that use the delivery address as vendor
+        product = self.env['product.product'].create({
+            'name': 'Product A',
+            'seller_ids': [(0, 0, {
+                'partner_id': delivery_address.id,
+                'min_qty': 1.0,
+                'price': 1.0,
+            })]
+        })
+
+        #create a purchase order with the delivery address as partner
+        po_form = Form(self.env['purchase.order'])
+        po_form.partner_id = delivery_address
+        with po_form.order_line.new() as po_line:
+            po_line.product_id = product
+            po_line.product_qty = 1.0
+        po = po_form.save()
+        po.button_confirm()
+
+        self.assertEqual(po.order_line.product_id.seller_ids.mapped('partner_id'), delivery_address)