fix: block serialized to non-serialized item change when SABB exists (backport #56773) (#56774)

* fix: block serialized to non-serialized item change when SABB exists (#56773)

(cherry picked from commit 0e8ae7548d)

# Conflicts:
#	erpnext/stock/doctype/item/item.py
#	erpnext/stock/doctype/item/test_item.py

* chore: fix conflicts

* chore: fix conflicts

Remove test for variant UOM mismatch and related logic.

---------

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

erpnext/stock/doctype/item/item.py

@@ -217,6 +217,7 @@ class Item(Document):
 		self.validate_item_defaults()
 		self.validate_auto_reorder_enabled_in_stock_settings()
 		self.cant_change()
+		self.validate_serialized_change_with_bundle()
 		self.validate_item_tax_net_rate_range()
 
 		if not self.is_new():
@@ -1074,6 +1075,25 @@ class Item(Document):
 
 			frappe.throw(msg, title=_("Linked with submitted documents"))
 
+	def validate_serialized_change_with_bundle(self):
+		"""Block turning a serialized item non-serialized while any Serial and Batch Bundle still exists
+		for it. Such bundles carry the item's serial numbers; the user must delete or cancel them first."""
+		if self.is_new() or self.has_serial_no or not self._doc_before_save:
+			return
+
+		# Only relevant when the item was serialized before and is now being unset.
+		if not self._doc_before_save.has_serial_no:
+			return
+
+		# Draft (docstatus 0) or submitted (docstatus 1) bundles block the change; cancelled ones don't.
+		if frappe.db.count("Serial and Batch Bundle", {"item_code": self.name, "docstatus": ("<", 2)}):
+			frappe.throw(
+				_(
+					"Cannot change Item {0} from serialized to non-serialized because a Serial and Batch Bundle exists for it. Please delete or cancel the Serial and Batch Bundle first."
+				).format(frappe.bold(self.name)),
+				title=_("Serial and Batch Bundle Exists"),
+			)
+
 	def _get_linked_submitted_documents(self, changed_fields: list[str]) -> dict[str, str] | None:
 		linked_doctypes = [
 			"Delivery Note Item",

erpnext/stock/doctype/item/test_item.py

@@ -966,6 +966,47 @@ class TestItem(FrappeTestCase):
 
 		self.assertRaises(frappe.ValidationError, item_doc.save)
 
+	def test_cannot_unset_serialized_while_bundle_exists(self):
+		from erpnext.stock.doctype.serial_and_batch_bundle.test_serial_and_batch_bundle import (
+			make_serial_batch_bundle,
+		)
+
+		item = make_item(
+			properties={"has_serial_no": 1, "is_stock_item": 1, "serial_no_series": "TSN-UNSET-.####"}
+		).name
+
+		serial_no = f"{item}-SN-01"
+		frappe.get_doc(
+			{"doctype": "Serial No", "serial_no": serial_no, "item_code": item, "company": "_Test Company"}
+		).insert()
+
+		# A draft (unsubmitted) Serial and Batch Bundle for the item must block the change.
+		bundle = make_serial_batch_bundle(
+			{
+				"item_code": item,
+				"warehouse": "_Test Warehouse - _TC",
+				"company": "_Test Company",
+				"qty": 1,
+				"rate": 100,
+				"voucher_type": "Stock Entry",
+				"serial_nos": [serial_no],
+				"type_of_transaction": "Inward",
+				"do_not_submit": True,
+				"ignore_sabb_validation": True,
+			}
+		)
+
+		doc = frappe.get_doc("Item", item)
+		doc.has_serial_no = 0
+		self.assertRaises(frappe.ValidationError, doc.save)
+
+		# Once the bundle is removed, the item can be made non-serialized.
+		frappe.delete_doc("Serial and Batch Bundle", bundle.name, force=True)
+		doc = frappe.get_doc("Item", item)
+		doc.has_serial_no = 0
+		doc.save()
+		self.assertEqual(frappe.db.get_value("Item", item, "has_serial_no"), 0)
+
 
 def set_item_variant_settings(fields):
 	doc = frappe.get_doc("Item Variant Settings")