fix(stock): support shared target UOM conversions (#58305)

erpnext/stock/doctype/item/item.py

@@ -1510,7 +1510,7 @@ def get_uom_conv_factor(uom: str | None, stock_uom: str | None):
 	inverse_match = frappe.db.get_value(
 		"UOM Conversion Factor", {"to_uom": from_uom, "from_uom": to_uom}, ["value"], as_dict=1
 	)
-	if inverse_match:
+	if inverse_match and inverse_match.value:
 		return flt(1 / inverse_match.value, frappe.get_precision("UOM Conversion Factor", "value"))
 
 	# This attempts to try and get conversion from intermediate UOM.
@@ -1520,18 +1520,34 @@ def get_uom_conv_factor(uom: str | None, stock_uom: str | None):
 	# therefore	 kg -> mg = 1000  / 0.001 = 1,000,000
 	first = frappe.qb.DocType("UOM Conversion Factor").as_("first")
 	second = frappe.qb.DocType("UOM Conversion Factor").as_("second")
-	intermediate_match = (
+	# Conversion pairs are not unique, so document names provide stable tie-breakers.
+	shared_source_match = (
 		frappe.qb.from_(first)
 		.join(second)
 		.on(first.from_uom == second.from_uom)
 		.select((first.value / second.value).as_("value"))
-		.where((first.to_uom == to_uom) & (second.to_uom == from_uom))
+		.where((first.to_uom == to_uom) & (second.to_uom == from_uom) & (second.value != 0))
+		.orderby(first.name, second.name)
 		.limit(1)
 		.run(as_dict=1)
 	)
 
-	if intermediate_match:
-		return flt(intermediate_match[0].value, frappe.get_precision("UOM Conversion Factor", "value"))
+	if shared_source_match:
+		return flt(shared_source_match[0].value, frappe.get_precision("UOM Conversion Factor", "value"))
+
+	shared_target_match = (
+		frappe.qb.from_(first)
+		.join(second)
+		.on(first.to_uom == second.to_uom)
+		.select((first.value / second.value).as_("value"))
+		.where((first.from_uom == from_uom) & (second.from_uom == to_uom) & (second.value != 0))
+		.orderby(first.name, second.name)
+		.limit(1)
+		.run(as_dict=1)
+	)
+
+	if shared_target_match:
+		return flt(shared_target_match[0].value, frappe.get_precision("UOM Conversion Factor", "value"))
 
 
 @frappe.whitelist()

erpnext/stock/doctype/item/test_item.py

@@ -71,6 +71,20 @@ def make_item(item_code=None, properties=None, uoms=None, barcode=None):
 	return item
 
 
+def make_uom_conversion_factor(from_uom, to_uom, value, category="Mass"):
+	for uom in (from_uom, to_uom):
+		if not frappe.db.exists("UOM", uom):
+			frappe.get_doc(doctype="UOM", uom_name=uom, category=category).insert()
+
+	return frappe.get_doc(
+		doctype="UOM Conversion Factor",
+		category=category,
+		from_uom=from_uom,
+		to_uom=to_uom,
+		value=value,
+	).insert()
+
+
 class TestItem(ERPNextTestSuite):
 	def setUp(self):
 		super().setUp()
@@ -807,6 +821,32 @@ class TestItem(ERPNextTestSuite):
 		factor = get_uom_conv_factor("Pound", "Gram")
 		self.assertAlmostEqual(factor, 453.592, 3)
 
+	def test_uom_conv_intermediate_with_shared_target(self):
+		make_uom_conversion_factor("_Test 3 Kg Bag", "Kg", 3)
+		make_uom_conversion_factor("_Test 25 Kg Bag", "Kg", 25)
+
+		factor = get_uom_conv_factor("_Test 3 Kg Bag", "_Test 25 Kg Bag")
+
+		self.assertEqual(factor, 0.12)
+
+	def test_uom_conv_intermediate_with_shared_target_is_deterministic(self):
+		make_uom_conversion_factor("_Test 3 Kg Bag", "Kg", 3)
+		make_uom_conversion_factor("_Test 25 Kg Bag", "Kg", 25)
+		make_uom_conversion_factor("_Test 3 Kg Bag", "Kg", 6)
+		make_uom_conversion_factor("_Test 25 Kg Bag", "Kg", 20)
+
+		factor = get_uom_conv_factor("_Test 3 Kg Bag", "_Test 25 Kg Bag")
+
+		self.assertEqual(factor, 0.12)
+
+	def test_uom_conv_intermediate_with_shared_target_ignores_zero_divisor(self):
+		make_uom_conversion_factor("_Test 3 Kg Bag", "Kg", 3)
+		make_uom_conversion_factor("_Test 25 Kg Bag", "Kg", 0)
+
+		factor = get_uom_conv_factor("_Test 3 Kg Bag", "_Test 25 Kg Bag")
+
+		self.assertIsNone(factor)
+
 	def test_uom_conv_base_case(self):
 		factor = get_uom_conv_factor("m", "m")
 		self.assertEqual(factor, 1.0)

erpnext/stock/doctype/purchase_receipt/test_purchase_receipt.py

@@ -15,7 +15,7 @@ from erpnext.buying.doctype.supplier.test_supplier import create_supplier
 from erpnext.controllers.accounts_controller import InvalidQtyError
 from erpnext.controllers.buying_controller import QtyMismatchError
 from erpnext.stock import get_warehouse_account_map
-from erpnext.stock.doctype.item.test_item import create_item, make_item
+from erpnext.stock.doctype.item.test_item import create_item, make_item, make_uom_conversion_factor
 from erpnext.stock.doctype.material_request.mapper import make_purchase_order
 from erpnext.stock.doctype.purchase_receipt.mapper import make_purchase_invoice
 from erpnext.stock.doctype.serial_and_batch_bundle.serial_and_batch_bundle import (
@@ -28,6 +28,7 @@ from erpnext.stock.doctype.serial_and_batch_bundle.test_serial_and_batch_bundle
 	make_serial_batch_bundle,
 )
 from erpnext.stock.doctype.warehouse.test_warehouse import create_warehouse
+from erpnext.stock.get_item_details import get_conversion_factor
 from erpnext.tests.utils import ERPNextTestSuite
 
 
@@ -4610,6 +4611,33 @@ class TestPurchaseReceipt(ERPNextTestSuite):
 
 		self.assertEqual(pr.items[0].conversion_factor, 1.0)
 
+	def test_conversion_factor_via_shared_target_uom(self):
+		transaction_uom = "_Test 3 Kg Bag"
+		stock_uom = "_Test 25 Kg Bag"
+		make_uom_conversion_factor(transaction_uom, "Kg", 3)
+		make_uom_conversion_factor(stock_uom, "Kg", 25)
+		item = make_item("Test Item for Shared Target UOM", {"stock_uom": stock_uom})
+
+		conversion_factor = get_conversion_factor(item.name, transaction_uom).get("conversion_factor")
+		pr = make_purchase_receipt(
+			item_code=item.name,
+			qty=10,
+			uom=transaction_uom,
+			stock_uom=stock_uom,
+			conversion_factor=conversion_factor,
+		)
+
+		self.assertEqual(conversion_factor, 0.12)
+		self.assertEqual(pr.items[0].stock_qty, 1.2)
+		self.assertEqual(
+			frappe.db.get_value(
+				"Stock Ledger Entry",
+				{"voucher_type": pr.doctype, "voucher_no": pr.name, "voucher_detail_no": pr.items[0].name},
+				"actual_qty",
+			),
+			1.2,
+		)
+
 	def test_purchase_receipt_return_valuation_without_use_serial_batch_field(self):
 		from erpnext.stock.doctype.purchase_receipt.mapper import make_purchase_return