[ADD] vendor_in_rr: auto-set best vendor in reordering rules

vendor_in_rr/__init__.py

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+from . import models

vendor_in_rr/__manifest__.py

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+{
+    "name": "Vendor In Reordering Rules",
+    "summary": "Automatically set the best vendor in Reordering Rules based on price and unit ratio",
+    "description": """
+        This module adds logic to automatically set the best vendor in stock reordering rules
+        during creation and editing based on price and unit ratio.
+    """,
+    "depends": ["stock", "purchase"],
+    "license": "LGPL-3",
+    "installable": True,
+}

vendor_in_rr/models/__init__.py

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+from . import stock_orderpoint

vendor_in_rr/models/stock_orderpoint.py

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+from odoo import api, models
+
+
+class StockWarehouseOrderpoint(models.Model):
+    _inherit = "stock.warehouse.orderpoint"
+
+    @api.onchange("route_id")
+    def _onchange_route_as_buy_set_supplier(self):
+        if (
+            self.product_id
+            and self.route_id
+            and "buy" in self.route_id.rule_ids.mapped("action")
+        ):
+            if not self.supplier_id:
+                best_supplier = self._get_best_supplier(self.product_id)
+                if best_supplier:
+                    self.supplier_id = best_supplier.id
+
+    def _get_best_supplier(self, product):
+        supplierinfos = self.env["product.supplierinfo"].search(
+            [
+                ("product_tmpl_id", "=", product.product_tmpl_id.id),
+            ]
+        )
+
+        best_supplier = False
+        best_effective_price = None
+
+        for supplier in supplierinfos:
+            # Normalize min_qty to product UoM
+            normalized_min_qty = supplier.product_uom._compute_quantity(
+                supplier.min_qty, product.uom_id
+            )
+
+            # Avoid division by zero
+            if normalized_min_qty <= 0:
+                continue
+
+            effective_price = supplier.price / normalized_min_qty
+
+            if (best_effective_price is None) or (
+                effective_price < best_effective_price
+            ):
+                best_effective_price = effective_price
+                best_supplier = supplier
+
+        return best_supplier