fix: item variant with manufacturer (backport #38845) (#38847)

* fix: item variant with manufacturer (#38845)

(cherry picked from commit e0c8ff10da)

* chore: fix test case

---------

Co-authored-by: rohitwaghchaure <rohitw1991@gmail.com>

erpnext/controllers/item_variant.py

@@ -56,10 +56,24 @@ def make_variant_based_on_manufacturer(template, manufacturer, manufacturer_part
 
 	copy_attributes_to_variant(template, variant)
 
-	variant.manufacturer = manufacturer
-	variant.manufacturer_part_no = manufacturer_part_no
-
 	variant.item_code = append_number_if_name_exists("Item", template.name)
+	variant.flags.ignore_mandatory = True
+	variant.save()
+
+	if not frappe.db.exists(
+		"Item Manufacturer", {"item_code": variant.name, "manufacturer": manufacturer}
+	):
+		manufacturer_doc = frappe.new_doc("Item Manufacturer")
+		manufacturer_doc.update(
+			{
+				"item_code": variant.name,
+				"manufacturer": manufacturer,
+				"manufacturer_part_no": manufacturer_part_no,
+			}
+		)
+
+		manufacturer_doc.flags.ignore_mandatory = True
+		manufacturer_doc.save(ignore_permissions=True)
 
 	return variant