fix: incorrect time period in asset depreciation schedule (backport #41805) (#42043)

fix: incorrect time period in asset depreciation schedule (#41805)

* fix(wip): depreciation calculation for existing asset

* fix(wip): added validation for incorrect depreciation period

* fix: depreciation schedule time period issue for existing asset

* chore: run pre-commit checks and apply fixes

* style: apply formatting changes

* style: made some necessary changes

* chore: modified test

(cherry picked from commit 625f16dee0)

Co-authored-by: Khushi Rawat <142375893+khushi8112@users.noreply.github.com>

erpnext/assets/doctype/asset/test_asset.py

@@ -1501,19 +1501,17 @@ class TestDepreciationBasics(AssetSetup):
 		"""
 
 		asset = create_asset(calculate_depreciation=1)
-		asset.opening_accumulated_depreciation = 2000
-		asset.opening_number_of_booked_depreciations = 1
 
 		asset.finance_books[0].expected_value_after_useful_life = 100
 		asset.save()
 		asset.reload()
-		self.assertEqual(asset.finance_books[0].value_after_depreciation, 98000.0)
+		self.assertEqual(asset.finance_books[0].value_after_depreciation, 100000.0)
 
 		# changing expected_value_after_useful_life shouldn't affect value_after_depreciation
 		asset.finance_books[0].expected_value_after_useful_life = 200
 		asset.save()
 		asset.reload()
-		self.assertEqual(asset.finance_books[0].value_after_depreciation, 98000.0)
+		self.assertEqual(asset.finance_books[0].value_after_depreciation, 100000.0)
 
 	def test_asset_cost_center(self):
 		asset = create_asset(is_existing_asset=1, do_not_save=1)

erpnext/assets/doctype/asset_depreciation_schedule/asset_depreciation_schedule.py

@@ -552,32 +552,45 @@ def _check_is_pro_rata(asset_doc, row, wdv_or_dd_non_yearly=False):
 	# if not existing asset, from_date = available_for_use_date
 	# otherwise, if opening_number_of_booked_depreciations = 2, available_for_use_date = 01/01/2020 and frequency_of_depreciation = 12
 	# from_date = 01/01/2022
-	from_date = _get_modified_available_for_use_date(asset_doc, row, wdv_or_dd_non_yearly)
+	from_date = _get_modified_available_for_use_date(asset_doc, row, wdv_or_dd_non_yearly=False)
 	days = date_diff(row.depreciation_start_date, from_date) + 1
-
-	if wdv_or_dd_non_yearly:
-		total_days = get_total_days(row.depreciation_start_date, 12)
-	else:
-		# if frequency_of_depreciation is 12 months, total_days = 365
-		total_days = get_total_days(row.depreciation_start_date, row.frequency_of_depreciation)
-
+	total_days = get_total_days(row.depreciation_start_date, row.frequency_of_depreciation)
+	if days <= 0:
+		frappe.throw(
+			_(
+				"""Error: This asset already has {0} depreciation periods booked.
+				The `depreciation start` date must be at least {1} periods after the `available for use` date.
+				Please correct the dates accordingly."""
+			).format(
+				asset_doc.opening_number_of_booked_depreciations,
+				asset_doc.opening_number_of_booked_depreciations,
+			)
+		)
 	if days < total_days:
 		has_pro_rata = True
-
 	return has_pro_rata
 
 
 def _get_modified_available_for_use_date(asset_doc, row, wdv_or_dd_non_yearly=False):
-	if wdv_or_dd_non_yearly:
-		return add_months(
+	"""
+	if Asset has opening booked depreciations = 9,
+	available for use date = 17-07-2023,
+	depreciation start date = 30-04-2024
+	then from date should be 01-04-2024
+	"""
+	if asset_doc.opening_number_of_booked_depreciations > 0:
+		from_date = add_months(
 			asset_doc.available_for_use_date,
-			(asset_doc.opening_number_of_booked_depreciations * 12),
+			(asset_doc.opening_number_of_booked_depreciations * row.frequency_of_depreciation) - 1,
 		)
+		if is_last_day_of_the_month(row.depreciation_start_date):
+			return add_days(get_last_day(from_date), 1)
+
+		# get from date when depreciation start date is not last day of the month
+		months_difference = month_diff(row.depreciation_start_date, from_date) - 1
+		return add_days(add_months(row.depreciation_start_date, -1 * months_difference), 1)
 	else:
-		return add_months(
-			asset_doc.available_for_use_date,
-			(asset_doc.opening_number_of_booked_depreciations * row.frequency_of_depreciation),
-		)
+		return asset_doc.available_for_use_date
 
 
 def _get_pro_rata_amt(

erpnext/assets/doctype/asset_depreciation_schedule/test_asset_depreciation_schedule.py

@@ -3,7 +3,7 @@
 
 import frappe
 from frappe.tests.utils import FrappeTestCase
-from frappe.utils import cstr
+from frappe.utils import cstr, flt
 
 from erpnext.assets.doctype.asset.depreciation import (
 	post_depreciation_entries,
@@ -172,7 +172,7 @@ class TestAssetDepreciationSchedule(FrappeTestCase):
 			opening_accumulated_depreciation=2000,
 			opening_number_of_booked_depreciations=2,
 			depreciation_method="Straight Line",
-			available_for_use_date="2020-03-01",
+			available_for_use_date="2020-01-01",
 			depreciation_start_date="2020-03-31",
 			frequency_of_depreciation=1,
 			total_number_of_depreciations=24,
@@ -195,3 +195,37 @@ class TestAssetDepreciationSchedule(FrappeTestCase):
 		asset.reload()
 
 		self.assertEqual(asset.finance_books[0].total_number_of_booked_depreciations, 14)
+
+	def test_schedule_for_wdv_method_for_existing_asset(self):
+		asset = create_asset(
+			calculate_depreciation=1,
+			depreciation_method="Written Down Value",
+			available_for_use_date="2020-07-17",
+			is_existing_asset=1,
+			opening_number_of_booked_depreciations=2,
+			opening_accumulated_depreciation=11666.67,
+			depreciation_start_date="2021-04-30",
+			total_number_of_depreciations=12,
+			frequency_of_depreciation=3,
+			gross_purchase_amount=50000,
+			rate_of_depreciation=40,
+		)
+
+		self.assertEqual(asset.status, "Draft")
+		expected_schedules = [
+			["2021-04-30", 3833.33, 15500.0],
+			["2021-07-31", 3833.33, 19333.33],
+			["2021-10-31", 3833.33, 23166.66],
+			["2022-01-31", 3833.33, 26999.99],
+			["2022-04-30", 2300.0, 29299.99],
+			["2022-07-31", 2300.0, 31599.99],
+			["2022-10-31", 2300.0, 33899.99],
+			["2023-01-31", 2300.0, 36199.99],
+			["2023-04-30", 1380.0, 37579.99],
+			["2023-07-31", 12420.01, 50000.0],
+		]
+		schedules = [
+			[cstr(d.schedule_date), flt(d.depreciation_amount, 2), d.accumulated_depreciation_amount]
+			for d in get_depr_schedule(asset.name, "Draft")
+		]
+		self.assertEqual(schedules, expected_schedules)