fix: purchase return of batchwise valuation batch valued at original receipt rate instead of batch avg rate (version-15-hotfix) (#57837)

* fix: use current batch avg rate for outward returns of batchwise valuation batches

* fix: honor zero batch average and avoid duplicate batch classification query

erpnext/stock/doctype/purchase_receipt/test_purchase_receipt.py

@@ -4996,6 +4996,66 @@ class TestPurchaseReceipt(FrappeTestCase):
 
 		self.assertEqual(frappe.parse_json(stock_queue), [[20, 0.0]])
 
+	def test_purchase_return_valuation_for_batchwise_valuation_batch(self):
+		from erpnext.controllers.sales_and_purchase_return import make_return_doc
+		from erpnext.stock.doctype.delivery_note.test_delivery_note import create_delivery_note
+
+		item_code = make_item(
+			"Test Purchase Return Batchwise Valn Item",
+			{
+				"is_stock_item": 1,
+				"has_batch_no": 1,
+				"batch_number_series": "BN-TPRBWV-.#####",
+			},
+		).name
+
+		batch_no = "BN-TPRBWV-00001"
+		batch = frappe.new_doc("Batch").update({"batch_id": batch_no, "item": item_code}).insert()
+		self.assertEqual(batch.use_batchwise_valuation, 1)
+
+		warehouse = "_Test Warehouse - _TC"
+		pr = make_purchase_receipt(
+			item_code=item_code,
+			qty=100,
+			rate=1000,
+			warehouse=warehouse,
+			batch_no=batch_no,
+			use_serial_batch_fields=1,
+		)
+		make_purchase_receipt(
+			item_code=item_code,
+			qty=100,
+			rate=400,
+			warehouse=warehouse,
+			batch_no=batch_no,
+			use_serial_batch_fields=1,
+		)
+		create_delivery_note(
+			item_code=item_code,
+			qty=100,
+			warehouse=warehouse,
+			batch_no=batch_no,
+			use_serial_batch_fields=1,
+		)
+
+		return_pr = make_return_doc("Purchase Receipt", pr.name)
+		return_pr.submit()
+
+		sle = frappe.db.get_value(
+			"Stock Ledger Entry",
+			{"voucher_no": return_pr.name, "is_cancelled": 0},
+			["stock_value_difference", "qty_after_transaction", "stock_value", "serial_and_batch_bundle"],
+			as_dict=True,
+		)
+		self.assertEqual(flt(sle.qty_after_transaction), 0.0)
+		self.assertEqual(flt(sle.stock_value_difference, 2), -70000.0)
+		self.assertEqual(flt(sle.stock_value, 2), 0.0)
+
+		rate = frappe.db.get_value(
+			"Serial and Batch Entry", {"parent": sle.serial_and_batch_bundle}, "incoming_rate"
+		)
+		self.assertEqual(flt(rate, 2), 700.0)
+
 	def test_negative_stock_error_for_purchase_return(self):
 		from erpnext.controllers.sales_and_purchase_return import make_return_doc
 		from erpnext.stock.doctype.stock_entry.test_stock_entry import make_stock_entry

erpnext/stock/doctype/serial_and_batch_bundle/serial_and_batch_bundle.py

@@ -402,6 +402,13 @@ class SerialandBatchBundle(Document):
 
 			valuation_method = get_valuation_method(self.item_code)
 
+			# An outward return must go out at the batch's current average rate for a
+			# batchwise valuation batch. The original receipt rate is only correct while
+			# the batch still holds stock at that rate; once other receipts have changed
+			# the average, removing at the original rate strands a residue in the batch
+			# value (negative when returning the costlier receipt).
+			batchwise_avg_rates = self.get_batchwise_return_avg_rates()
+
 			stock_queue = []
 			non_batchwise_batches = []
 			if not self.has_serial_no and valuation_method == "FIFO":
@@ -435,6 +442,12 @@ class SerialandBatchBundle(Document):
 						batches = sorted(list(valuation_details["batches"].keys()))
 						valuation_rate = valuation_details["batches"].get(batches[cint(row.idx) - 1])
 
+				# a batch with an available balance goes out at its current average rate (a
+				# valid 0.0 included); the original receipt rate applies only when there is
+				# no balance to average
+				if not row.serial_no and row.batch_no in batchwise_avg_rates:
+					valuation_rate = batchwise_avg_rates[row.batch_no]
+
 				row.incoming_rate = flt(valuation_rate)
 				row.stock_value_difference = flt(row.qty) * flt(row.incoming_rate)
 
@@ -463,6 +476,41 @@ class SerialandBatchBundle(Document):
 		elif self.type_of_transaction == "Inward":
 			self.set_incoming_rate_for_inward_transaction(row, save, prev_sle=prev_sle)
 
+	def get_batchwise_return_avg_rates(self):
+		from erpnext.stock.utils import get_valuation_method
+
+		if self.type_of_transaction != "Outward" or self.has_serial_no:
+			return {}
+
+		batch_nos = [d.batch_no for d in self.entries if d.batch_no]
+		if not batch_nos:
+			return {}
+
+		if get_valuation_method(self.item_code) == "Moving Average" and frappe.db.get_single_value(
+			"Stock Settings", "do_not_use_batchwise_valuation"
+		):
+			return {}
+
+		batchwise_batches = frappe.get_all(
+			"Batch",
+			filters={"name": ("in", batch_nos), "use_batchwise_valuation": 1},
+			pluck="name",
+		)
+		if not batchwise_batches:
+			return {}
+
+		# scoped to batchwise batches only, so BatchNoValuation's non-batchwise
+		# machinery never runs for them
+		sle = self.get_sle_for_outward_transaction()
+		sle.batch_nos = {batch_no: sle.batch_nos[batch_no] for batch_no in batchwise_batches}
+		sle.batchwise_valuation_batches = batchwise_batches
+		sn_obj = BatchNoValuation(sle=sle, item_code=self.item_code, warehouse=self.warehouse)
+		return {
+			batch_no: abs(flt(sn_obj.batch_avg_rate.get(batch_no)))
+			for batch_no in batchwise_batches
+			if flt(sn_obj.available_qty.get(batch_no))
+		}
+
 	def validate_returned_serial_batch_no(self, return_against, row, original_inv_details):
 		if frappe.flags.through_repost_item_valuation:
 			return

erpnext/stock/serial_batch_bundle.py

@@ -910,6 +910,11 @@ class BatchNoValuation(DeprecatedBatchNoValuation):
 		self.batchwise_valuation_batches = []
 		self.non_batchwise_valuation_batches = []
 
+		if batchwise_batches := self.sle.get("batchwise_valuation_batches"):
+			self.batchwise_valuation_batches = list(batchwise_batches)
+			self.non_batchwise_valuation_batches = list(set(self.batches) - set(batchwise_batches))
+			return
+
 		if get_valuation_method(self.sle.item_code) == "Moving Average" and frappe.db.get_single_value(
 			"Stock Settings", "do_not_use_batchwise_valuation"
 		):