fix: updated packed_items getting fetched on Sales Return / Credit Note (#28607)

* fix: updated packed_items getting fetched on sales return

* fix: updated test cases for product bundle returns

* fix: moved calculate_mapped_packed_items_return to stock.utils

* fix: updated packed_items getting fetched on Return/Credit Note

* refactor: change var name to avoid `self`

* fix: check item code before assigning parent item

Co-authored-by: Ankush Menat <ankush@frappe.io>
diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index 98bc953..f04e7ea 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -43,6 +43,7 @@
 from erpnext.stock.doctype.batch.batch import set_batch_nos
 from erpnext.stock.doctype.delivery_note.delivery_note import update_billed_amount_based_on_so
 from erpnext.stock.doctype.serial_no.serial_no import get_delivery_note_serial_no, get_serial_nos
+from erpnext.stock.utils import calculate_mapped_packed_items_return
 
 form_grid_templates = {
 	"items": "templates/form_grid/item_grid.html"
@@ -728,8 +729,11 @@
 
 	def update_packing_list(self):
 		if cint(self.update_stock) == 1:
-			from erpnext.stock.doctype.packed_item.packed_item import make_packing_list
-			make_packing_list(self)
+			if cint(self.is_return) and self.return_against:
+				calculate_mapped_packed_items_return(self)
+			else:
+				from erpnext.stock.doctype.packed_item.packed_item import make_packing_list
+				make_packing_list(self)
 		else:
 			self.set('packed_items', [])
 
diff --git a/erpnext/stock/doctype/delivery_note/delivery_note.py b/erpnext/stock/doctype/delivery_note/delivery_note.py
index 70d48a4..d1e2244 100644
--- a/erpnext/stock/doctype/delivery_note/delivery_note.py
+++ b/erpnext/stock/doctype/delivery_note/delivery_note.py
@@ -14,6 +14,7 @@
 from erpnext.controllers.selling_controller import SellingController
 from erpnext.stock.doctype.batch.batch import set_batch_nos
 from erpnext.stock.doctype.serial_no.serial_no import get_delivery_note_serial_no
+from erpnext.stock.utils import calculate_mapped_packed_items_return
 
 form_grid_templates = {
 	"items": "templates/form_grid/item_grid.html"
@@ -128,8 +129,12 @@
 		self.validate_uom_is_integer("uom", "qty")
 		self.validate_with_previous_doc()
 
-		from erpnext.stock.doctype.packed_item.packed_item import make_packing_list
-		make_packing_list(self)
+		# Keeps mapped packed_items in case product bundle is updated.
+		if self.is_return and self.return_against:
+			calculate_mapped_packed_items_return(self)
+		else:
+			from erpnext.stock.doctype.packed_item.packed_item import make_packing_list
+			make_packing_list(self)
 
 		if self._action != 'submit' and not self.is_return:
 			set_batch_nos(self, 'warehouse', throw=True)
diff --git a/erpnext/stock/doctype/delivery_note/test_delivery_note.py b/erpnext/stock/doctype/delivery_note/test_delivery_note.py
index 4f89a19..bd18e78 100644
--- a/erpnext/stock/doctype/delivery_note/test_delivery_note.py
+++ b/erpnext/stock/doctype/delivery_note/test_delivery_note.py
@@ -386,8 +386,7 @@
 		self.assertEqual(actual_qty, 25)
 
 		#  return bundled item
-		dn1 = create_delivery_note(item_code='_Test Product Bundle Item', is_return=1,
-			return_against=dn.name, qty=-2, rate=500, company=company, warehouse="Stores - TCP1", expense_account="Cost of Goods Sold - TCP1", cost_center="Main - TCP1")
+		dn1 = create_return_delivery_note(source_name=dn.name, rate=500, qty=-2)
 
 		# qty after return
 		actual_qty = get_qty_after_transaction(warehouse="Stores - TCP1")
@@ -823,6 +822,15 @@
 
 		automatically_fetch_payment_terms(enable=0)
 
+def create_return_delivery_note(**args):
+	args = frappe._dict(args)
+	from erpnext.controllers.sales_and_purchase_return import make_return_doc
+	doc = make_return_doc("Delivery Note", args.source_name, None)
+	doc.items[0].rate = args.rate
+	doc.items[0].qty = args.qty
+	doc.submit()
+	return doc
+
 def create_delivery_note(**args):
 	dn = frappe.new_doc("Delivery Note")
 	args = frappe._dict(args)
diff --git a/erpnext/stock/doctype/stock_ledger_entry/test_stock_ledger_entry.py b/erpnext/stock/doctype/stock_ledger_entry/test_stock_ledger_entry.py
index cafbd75..a1030d5 100644
--- a/erpnext/stock/doctype/stock_ledger_entry/test_stock_ledger_entry.py
+++ b/erpnext/stock/doctype/stock_ledger_entry/test_stock_ledger_entry.py
@@ -5,7 +5,10 @@
 from frappe.core.page.permission_manager.permission_manager import reset
 from frappe.utils import add_days, today
 
-from erpnext.stock.doctype.delivery_note.test_delivery_note import create_delivery_note
+from erpnext.stock.doctype.delivery_note.test_delivery_note import (
+	create_delivery_note,
+	create_return_delivery_note,
+)
 from erpnext.stock.doctype.item.test_item import make_item
 from erpnext.stock.doctype.landed_cost_voucher.test_landed_cost_voucher import (
 	create_landed_cost_voucher,
@@ -232,8 +235,7 @@
 		self.assertEqual(outgoing_rate, 100)
 
 		# Return Entry: Qty = -2, Rate = 150
-		return_dn = create_delivery_note(is_return=1, return_against=dn.name, item_code=bundled_item, qty=-2, rate=150,
-			company=company, warehouse="Stores - _TC", expense_account="Cost of Goods Sold - _TC", cost_center="Main - _TC")
+		return_dn = create_return_delivery_note(source_name=dn.name, rate=150, qty=-2)
 
 		# check incoming rate for Return entry
 		incoming_rate, stock_value_difference = frappe.db.get_value("Stock Ledger Entry",
diff --git a/erpnext/stock/utils.py b/erpnext/stock/utils.py
index 3c70b41..1a846f0 100644
--- a/erpnext/stock/utils.py
+++ b/erpnext/stock/utils.py
@@ -419,6 +419,19 @@
 	if reposting_in_progress:
 		frappe.msgprint(_("Item valuation reposting in progress. Report might show incorrect item valuation."), alert=1)
 
+
+def calculate_mapped_packed_items_return(return_doc):
+	parent_items = set([item.parent_item for item in return_doc.packed_items])
+	against_doc = frappe.get_doc(return_doc.doctype, return_doc.return_against)
+
+	for original_bundle, returned_bundle in zip(against_doc.items, return_doc.items):
+		if original_bundle.item_code in parent_items:
+			for returned_packed_item, original_packed_item in zip(return_doc.packed_items, against_doc.packed_items):
+				if returned_packed_item.parent_item == original_bundle.item_code:
+					returned_packed_item.parent_detail_docname = returned_bundle.name
+					returned_packed_item.qty = (original_packed_item.qty / original_bundle.qty) * returned_bundle.qty
+
+
 def check_pending_reposting(posting_date: str, throw_error: bool = True) -> bool:
 	"""Check if there are pending reposting job till the specified posting date."""