fix: disallow BOM finished good item in secondary items table (backport #55710) (#55719)

Co-authored-by: Mihir Kandoi <kandoimihir@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
fix: disallow BOM finished good item in secondary items table (#55710)

erpnext/manufacturing/doctype/bom/bom.py

@@ -334,6 +334,13 @@ class BOM(WebsiteGenerator):
 
 	def validate_secondary_items(self):
 		for item in self.secondary_items:
+			if not item.is_legacy and item.item_code == self.item:
+				frappe.throw(
+					_(
+						"Row #{0}: Finished Good Item {1} cannot be added in the Secondary Items table."
+					).format(item.idx, get_link_to_form("Item", item.item_code))
+				)
+
 			if not item.qty:
 				frappe.throw(
 					_("Row #{0}: Quantity should be greater than 0 for {1} Item {2}").format(

erpnext/manufacturing/doctype/bom/test_bom.py

@@ -444,6 +444,30 @@ class TestBOM(ERPNextTestSuite):
 		#  Items with whole UOMs can't be PL Items
 		self.assertRaises(frappe.ValidationError, bom_doc.submit)
 
+	@timeout
+	def test_fg_item_not_allowed_in_secondary_items(self):
+		fg_item = make_item(properties={"is_stock_item": 1, "valuation_rate": 100}).name
+		rm_item = make_item(properties={"is_stock_item": 1, "valuation_rate": 100}).name
+
+		bom_doc = frappe.new_doc("BOM")
+		bom_doc.item = fg_item
+		bom_doc.quantity = 1
+		bom_doc.company = "_Test Company"
+		bom_doc.currency = "INR"
+		bom_doc.append("items", {"item_code": rm_item, "qty": 1, "rate": 100.0})
+		bom_doc.append(
+			"secondary_items",
+			{
+				"item_code": fg_item,
+				"secondary_item_type": "Additional Finished Good",
+				"qty": 1,
+				"cost_allocation_per": 10,
+			},
+		)
+
+		# FG item of the BOM cannot also be a secondary item
+		self.assertRaises(frappe.ValidationError, bom_doc.save)
+
 	@timeout
 	def test_bom_item_query(self):
 		query = partial(