fix(stock): assign batch_no only when the first batch covers the full qty (#58668)

* fix(stock): assign batch_no only when the first batch covers the full qty

The auto-pick loop reduced the requested qty per batch and left the last
visited batch on the row, so a qty spanning batches got a batch that could
not fulfil it and failed at submit with a misleading negative-stock error.

Assign the first batch in pick order only when it alone covers the qty.
Otherwise leave batch_no empty so the auto-created Serial and Batch Bundle
splits the qty across batches at submit.

Batches are queried without qty so filter_batches subtracts rows already in
the document from the uncapped batch quantities. Querying on a copy also
stops get_auto_batch_nos from clearing warehouse on the kwargs later used to
pick serial nos.

Fixes #58640

* test(stock): cover batch auto-pick when qty spans batches

* fix(stock): pick serial nos across batches when no batch covers the qty

With batch_no left empty for a qty that spans batches, the serial pick for a
serialised and batched item filtered on [None] and returned nothing, leaving
the row with neither identity. Skip the batch filter when there is no batch so
the serial nos are picked in the configured order across batches; the bundle
built at submit derives each serial's batch.

* test(stock): cover serial pick across batches for batched serial items

erpnext/stock/get_item_details.py

@@ -292,7 +292,6 @@ def set_valuation_rate(out: frappe._dict, ctx: frappe._dict):
 
 
 def update_stock(ctx, out, doc=None):
-	from erpnext.stock.doctype.batch.batch import get_available_batches
 	from erpnext.stock.doctype.serial_no.serial_no import get_serial_nos_for_outward
 
 	if (
@@ -325,32 +324,21 @@ def update_stock(ctx, out, doc=None):
 		if ctx.get("ignore_serial_nos"):
 			kwargs["ignore_serial_nos"] = ctx.get("ignore_serial_nos")
 
-		qty = out.stock_qty
-		batches = []
 		if out.has_batch_no and not ctx.get("batch_no"):
-			batches = get_available_batches(kwargs)
-			if doc:
-				filter_batches(batches, doc)
-
-			for batch_no, batch_qty in batches.items():
+			batch_no = get_batch_no_covering_qty(kwargs, doc, out.stock_qty)
+			if batch_no:
+				out.update({"batch_no": batch_no, "actual_batch_qty": out.stock_qty})
 				rate = get_batch_based_item_price(
 					{"price_list": doc.get("selling_price_list"), "uom": out.uom, "batch_no": batch_no},
 					out.item_code,
 				)
-				if batch_qty >= qty:
-					out.update({"batch_no": batch_no, "actual_batch_qty": qty})
-					if rate:
-						out.update({"rate": rate, "price_list_rate": rate})
-					break
-				else:
-					qty -= batch_qty
-
-				out.update({"batch_no": batch_no, "actual_batch_qty": batch_qty})
 				if rate:
 					out.update({"rate": rate, "price_list_rate": rate})
 
 		if out.has_serial_no and out.has_batch_no and has_incorrect_serial_nos(ctx, out):
-			kwargs["batches"] = [ctx.get("batch_no")] if ctx.get("batch_no") else [out.get("batch_no")]
+			batch_no = ctx.get("batch_no") or out.get("batch_no")
+			if batch_no:
+				kwargs["batches"] = [batch_no]
 			serial_nos = get_serial_nos_for_outward(kwargs)
 			serial_nos = get_filtered_serial_nos(serial_nos, doc)
 
@@ -376,6 +364,20 @@ def has_incorrect_serial_nos(ctx, out):
 	return False
 
 
+def get_batch_no_covering_qty(kwargs, doc, qty):
+	from erpnext.stock.doctype.batch.batch import get_available_batches
+
+	batches = get_available_batches(frappe._dict(kwargs, qty=0))
+	if doc:
+		filter_batches(batches, doc)
+
+	batch_no = next(iter(batches), None)
+	if batch_no and flt(batches[batch_no]) >= flt(qty):
+		return batch_no
+
+	return None
+
+
 def filter_batches(batches, doc):
 	for row in doc.get("items"):
 		if row.get("batch_no") in batches:

erpnext/stock/tests/test_get_item_details.py

@@ -457,3 +457,93 @@ class TestGetItemDetail(ERPNextTestSuite):
 			frappe.set_user("Administrator")
 			frappe.db.set_single_value("Buying Settings", "maintain_same_rate", original)
 			frappe.clear_cache(doctype="Buying Settings")
+
+	def make_batched_item_with_stock(self, quantities, uoms=None, **properties):
+		from erpnext.stock.doctype.item.test_item import make_item
+		from erpnext.stock.doctype.serial_and_batch_bundle.test_serial_and_batch_bundle import (
+			get_batch_from_bundle,
+		)
+		from erpnext.stock.doctype.stock_entry.test_stock_entry import make_stock_entry
+
+		properties.update({"has_batch_no": 1, "create_new_batch": 1, "batch_number_series": "FBQ-.#####"})
+		item_code = make_item(properties=properties, uoms=uoms).name
+		batches = []
+		for qty in quantities:
+			se = make_stock_entry(
+				item_code=item_code, target="_Test Warehouse - _TC", qty=qty, basic_rate=100
+			)
+			batches.append(get_batch_from_bundle(se.items[0].serial_and_batch_bundle))
+
+		return item_code, batches
+
+	def get_item_details_for_row(self, item_code, qty, items=None):
+		ctx = frappe._dict(
+			{
+				"doctype": "Delivery Note",
+				"item_code": item_code,
+				"company": "_Test Company",
+				"warehouse": "_Test Warehouse - _TC",
+				"qty": qty,
+				"use_serial_batch_fields": 1,
+				"price_list": "_Test Price List",
+				"currency": "INR",
+				"conversion_rate": 1.0,
+				"price_list_currency": "INR",
+				"plc_conversion_rate": 1.0,
+				"ignore_pricing_rule": 1,
+			}
+		)
+		doc = {"doctype": "Delivery Note", "selling_price_list": "_Test Price List", "items": items or []}
+		return get_item_details(ctx, doc=doc)
+
+	def get_picked_batch_no(self, item_code, qty, items=None):
+		return self.get_item_details_for_row(item_code, qty, items).get("batch_no")
+
+	def test_batch_no_set_only_when_first_batch_covers_qty(self):
+		from erpnext.stock.doctype.delivery_note.test_delivery_note import create_delivery_note
+
+		item_code, batches = self.make_batched_item_with_stock([2, 3, 14])
+		first_batch_row = [{"batch_no": batches[0], "qty": 2, "stock_qty": 2}]
+
+		with self.change_settings(
+			"Stock Settings",
+			{"pick_serial_and_batch_based_on": "FIFO", "auto_create_serial_and_batch_bundle_for_outward": 1},
+		):
+			self.assertEqual(self.get_picked_batch_no(item_code, 2), batches[0])
+			self.assertEqual(self.get_picked_batch_no(item_code, 3, items=first_batch_row), batches[1])
+			self.assertIsNone(self.get_picked_batch_no(item_code, 5))
+			self.assertIsNone(self.get_picked_batch_no(item_code, 20))
+
+			dn = create_delivery_note(item_code=item_code, qty=5, use_serial_batch_fields=1)
+			dn.reload()
+			entries = frappe.get_all(
+				"Serial and Batch Entry", {"parent": dn.items[0].serial_and_batch_bundle}, ["batch_no", "qty"]
+			)
+			self.assertEqual({d.batch_no: d.qty for d in entries}, {batches[0]: -2, batches[1]: -3})
+
+	def test_serial_nos_picked_across_batches_when_no_batch_covers_qty(self):
+		from erpnext.stock.doctype.delivery_note.test_delivery_note import create_delivery_note
+		from erpnext.stock.doctype.serial_and_batch_bundle.test_serial_and_batch_bundle import (
+			get_serial_nos_from_bundle,
+		)
+
+		item_code, batches = self.make_batched_item_with_stock(
+			[2, 3], has_serial_no=1, serial_no_series="FBQ-SN-.#####"
+		)
+
+		with self.change_settings(
+			"Stock Settings",
+			{"pick_serial_and_batch_based_on": "FIFO", "auto_create_serial_and_batch_bundle_for_outward": 1},
+		):
+			details = self.get_item_details_for_row(item_code, 5)
+			self.assertIsNone(details.get("batch_no"))
+			serial_nos = details.serial_no.split("\n")
+			self.assertEqual(len(serial_nos), 5)
+
+			dn = create_delivery_note(
+				item_code=item_code, qty=5, use_serial_batch_fields=1, serial_no=details.serial_no
+			)
+			dn.reload()
+			self.assertEqual(
+				get_serial_nos_from_bundle(dn.items[0].serial_and_batch_bundle), sorted(serial_nos)
+			)