test(purchase): add coverage for zero-qty return rejection

erpnext/controllers/tests/test_sales_and_purchase_return.py

@@ -37,3 +37,44 @@ class TestSalesAndPurchaseReturn(ERPNextTestSuite):
 
 		self.assertEqual(return_dn.is_return, 1)
 		self.assertEqual(return_dn.items[0].qty, -5)
+
+	def test_purchase_invoice_zero_qty_return_is_rejected(self):
+		# A return with every item at qty 0 moves no stock and no value, so it must be
+		# rejected the same way a return with no items at all would be.
+		from erpnext.accounts.doctype.purchase_invoice.test_purchase_invoice import make_purchase_invoice
+
+		pi = make_purchase_invoice(qty=10)
+		self.addCleanup(self._cancel_and_delete, "Purchase Invoice", pi.name)
+
+		return_pi = make_purchase_invoice(
+			is_return=1,
+			return_against=pi.name,
+			qty=0,
+			do_not_save=True,
+		)
+
+		self.assertRaises(frappe.ValidationError, return_pi.save)
+
+	def test_purchase_invoice_item_name_only_zero_qty_return_is_rejected(self):
+		# Item Code is not mandatory on Purchase Invoice Item - a row can have only an
+		# item_name (e.g. a free-text/non-stock line). Such rows fall through to the
+		# item_name-only branch, which must also reject an all-zero-qty return instead
+		# of unconditionally treating the row as returned.
+		from erpnext.accounts.doctype.purchase_invoice.test_purchase_invoice import make_purchase_invoice
+
+		pi = make_purchase_invoice(item_name="_Test Item", qty=10, do_not_submit=True)
+		pi.items[0].item_code = ""
+		pi.save()
+		pi.submit()
+		self.addCleanup(self._cancel_and_delete, "Purchase Invoice", pi.name)
+
+		return_pi = make_purchase_invoice(
+			item_name="_Test Item",
+			is_return=1,
+			return_against=pi.name,
+			qty=0,
+			do_not_save=True,
+		)
+		return_pi.items[0].item_code = ""
+
+		self.assertRaises(frappe.ValidationError, return_pi.save)