[IMP] website_sale: warn for open cart on partner pricelist change

It is not always immediately clear to the end user that changing the
pricelist on a partner will not change the pricelist for any open carts
related to this partner. To clarify, this commit introduces a warning
message, indicating that the end user should change the pricelists of
these open carts manually if this is the desired effect.

Any open carts that already have the same pricelist as the new partner
pricelist are excluded from the search and will not trigger the warning
message.

task-2635067

closes odoo/odoo#77298

Signed-off-by: Romain Derie (rde) <rde@odoo.com>

addons/website_sale/models/res_partner.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo import api, fields, models
+from odoo import api, fields, models, _
 from odoo.addons.website.models import ir_http
 
 
@@ -18,8 +18,29 @@ class ResPartner(models.Model):
             if website and not is_public:
                 partner.last_website_so_id = SaleOrder.search([
                     ('partner_id', '=', partner.id),
+                    ('pricelist_id', '=', partner.property_product_pricelist.id),
                     ('website_id', '=', website.id),
                     ('state', '=', 'draft'),
                 ], order='write_date desc', limit=1)
             else:
                 partner.last_website_so_id = SaleOrder  # Not in a website context or public User
+
+    @api.onchange('property_product_pricelist')
+    def _onchange_property_product_pricelist(self):
+        open_order = self.env['sale.order'].search([
+            ('partner_id', '=', self._origin.id),
+            ('pricelist_id', '=', self._origin.property_product_pricelist.id),
+            ('pricelist_id', '!=', self.property_product_pricelist.id),
+            ('website_id', '!=', False),
+            ('state', '=', 'draft'),
+        ], limit=1)
+
+        if open_order:
+            return {'warning': {
+                'title': _('Open Sale Orders'),
+                'message': _(
+                    "This partner has an open cart. "
+                    "Please note that the pricelist will not be updated on that cart. "
+                    "Also, the cart might not be visible for the customer until you update the pricelist of that cart."
+                ),
+            }}