fix(wip): depreciation calculation after asset value adjustment

(cherry picked from commit d3200fb67f)

erpnext/assets/doctype/asset_depreciation_schedule/asset_depreciation_schedule.py

@@ -637,49 +637,18 @@ def get_straight_line_or_manual_depr_amount(
 	elif asset.flags.decrease_in_asset_value_due_to_value_adjustment:
 		if row.daily_prorata_based:
 			amount = flt(row.value_after_depreciation) - flt(row.expected_value_after_useful_life)
-			total_days = (
+			total_years = flt(number_of_pending_depreciations * row.frequency_of_depreciation) / 12
-				date_diff(
+			every_year_depr = amount / total_years
-					get_last_day(
-						add_months(
-							row.depreciation_start_date,
-							flt(row.total_number_of_depreciations - asset.number_of_depreciations_booked - 1)
-							* row.frequency_of_depreciation,
-						)
-					),
-					add_days(
-						get_last_day(
-							add_months(
-								row.depreciation_start_date,
-								flt(
-									row.total_number_of_depreciations
-									- asset.number_of_depreciations_booked
-									- number_of_pending_depreciations
-									- 1
-								)
-								* row.frequency_of_depreciation,
-							)
-						),
-						1,
-					),
-				)
-				+ 1
-			)
 
-			daily_depr_amount = amount / total_days
+			year_start_date = add_years(
-
+				row.depreciation_start_date, (row.frequency_of_depreciation * schedule_idx) // 12
-			to_date = get_last_day(
-				add_months(row.depreciation_start_date, schedule_idx * row.frequency_of_depreciation)
 			)
-			from_date = add_days(
+			year_end_date = add_days(add_years(year_start_date, 1), -1)
-				get_last_day(
+			daily_depr_amount = every_year_depr / (date_diff(year_end_date, year_start_date) + 1)
-					add_months(
+			total_depreciable_days = _get_total_days(
-						row.depreciation_start_date, (schedule_idx - 1) * row.frequency_of_depreciation
+				row.depreciation_start_date, schedule_idx, row.frequency_of_depreciation
 			)
-				),
+			return daily_depr_amount * total_depreciable_days
-				1,
-			)
-
-			return daily_depr_amount * (date_diff(to_date, from_date) + 1)
 		else:
 			return (
 				flt(row.value_after_depreciation) - flt(row.expected_value_after_useful_life)
@@ -692,40 +661,24 @@ def get_straight_line_or_manual_depr_amount(
 				- flt(asset.opening_accumulated_depreciation)
 				- flt(row.expected_value_after_useful_life)
 			)
+			total_years = (
+				flt(
+					(row.total_number_of_depreciations - asset.number_of_depreciations_booked)
+					* row.frequency_of_depreciation
+				)
+				/ 12
+			)
+			every_year_depr = amount / total_years
 
-			total_days = (
+			year_start_date = add_years(
-				date_diff(
+				row.depreciation_start_date, (row.frequency_of_depreciation * schedule_idx) // 12
-					get_last_day(
-						add_months(
-							row.depreciation_start_date,
-							flt(row.total_number_of_depreciations - asset.number_of_depreciations_booked - 1)
-							* row.frequency_of_depreciation,
 			)
-					),
+			year_end_date = add_days(add_years(year_start_date, 1), -1)
-					add_days(
+			daily_depr_amount = every_year_depr / (date_diff(year_end_date, year_start_date) + 1)
-						get_last_day(
+			total_depreciable_days = _get_total_days(
-							add_months(row.depreciation_start_date, -1 * row.frequency_of_depreciation)
+				row.depreciation_start_date, schedule_idx, row.frequency_of_depreciation
-						),
-						1,
-					),
 			)
-				+ 1
+			return daily_depr_amount * total_depreciable_days
-			)
-
-			daily_depr_amount = amount / total_days
-
-			to_date = get_last_day(
-				add_months(row.depreciation_start_date, schedule_idx * row.frequency_of_depreciation)
-			)
-			from_date = add_days(
-				get_last_day(
-					add_months(
-						row.depreciation_start_date, (schedule_idx - 1) * row.frequency_of_depreciation
-					)
-				),
-				1,
-			)
-			return daily_depr_amount * (date_diff(to_date, from_date) + 1)
 		else:
 			return (
 				flt(asset.gross_purchase_amount)
@@ -734,6 +687,15 @@ def get_straight_line_or_manual_depr_amount(
 			) / flt(row.total_number_of_depreciations - asset.number_of_depreciations_booked)
 
 
+def _get_total_days(depreciation_start_date, schedule_idx, frequency_of_depreciation):
+	from_date = add_months(depreciation_start_date, (schedule_idx - 1) * frequency_of_depreciation)
+	to_date = add_months(from_date, frequency_of_depreciation)
+	if is_last_day_of_the_month(depreciation_start_date):
+		to_date = get_last_day(to_date)
+		from_date = add_days(get_last_day(from_date), 1)
+	return date_diff(to_date, from_date) + 1
+
+
 def get_shift_depr_amount(asset_depr_schedule, asset, row, schedule_idx):
 	if asset_depr_schedule.get("__islocal") and not asset.flags.shift_allocation:
 		return (

erpnext/assets/doctype/asset_depreciation_schedule/test_asset_depreciation_schedule.py

@@ -3,10 +3,12 @@
 
 import frappe
 from frappe.tests.utils import FrappeTestCase
+from frappe.utils import cstr
 
 from erpnext.assets.doctype.asset.test_asset import create_asset, create_asset_data
 from erpnext.assets.doctype.asset_depreciation_schedule.asset_depreciation_schedule import (
 	get_asset_depr_schedule_doc,
+	get_depr_schedule,
 )
 
 
@@ -25,3 +27,47 @@ class TestAssetDepreciationSchedule(FrappeTestCase):
 		)
 
 		self.assertRaises(frappe.ValidationError, second_asset_depr_schedule.insert)
+
+	def test_daily_prorata_based_depr_on_sl_methond(self):
+		asset = create_asset(
+			calculate_depreciation=1,
+			depreciation_method="Straight Line",
+			daily_prorata_based=1,
+			available_for_use_date="2020-01-01",
+			depreciation_start_date="2020-01-31",
+			frequency_of_depreciation=1,
+			total_number_of_depreciations=24,
+		)
+
+		expected_schedules = [
+			["2020-01-31", 4234.97, 4234.97],
+			["2020-02-29", 3961.75, 8196.72],
+			["2020-03-31", 4234.97, 12431.69],
+			["2020-04-30", 4098.36, 16530.05],
+			["2020-05-31", 4234.97, 20765.02],
+			["2020-06-30", 4098.36, 24863.38],
+			["2020-07-31", 4234.97, 29098.35],
+			["2020-08-31", 4234.97, 33333.32],
+			["2020-09-30", 4098.36, 37431.68],
+			["2020-10-31", 4234.97, 41666.65],
+			["2020-11-30", 4098.36, 45765.01],
+			["2020-12-31", 4234.97, 49999.98],
+			["2021-01-31", 4246.58, 54246.56],
+			["2021-02-28", 3835.62, 58082.18],
+			["2021-03-31", 4246.58, 62328.76],
+			["2021-04-30", 4109.59, 66438.35],
+			["2021-05-31", 4246.58, 70684.93],
+			["2021-06-30", 4109.59, 74794.52],
+			["2021-07-31", 4246.58, 79041.1],
+			["2021-08-31", 4246.58, 83287.68],
+			["2021-09-30", 4109.59, 87397.27],
+			["2021-10-31", 4246.58, 91643.85],
+			["2021-11-30", 4109.59, 95753.44],
+			["2021-12-31", 4246.56, 100000.0],
+		]
+
+		schedules = [
+			[cstr(d.schedule_date), d.depreciation_amount, d.accumulated_depreciation_amount]
+			for d in get_depr_schedule(asset.name, "Draft")
+		]
+		self.assertEqual(schedules, expected_schedules)