fix: depreciation schedule for existing assets [v14] (backport #35255) (#35347)

* fix: depreciation schedule for existing assets [v14] (#35255)

* fix: depreciation schedule for existing assets

* chore: correct logic for existing assets and fix test

(cherry picked from commit 0a080efce2)

# Conflicts:
#	erpnext/assets/doctype/asset/asset.py

* chore: fix conflict

---------

Co-authored-by: Anand Baburajan <anandbaburajan@gmail.com>

erpnext/assets/doctype/asset/asset.py

@@ -432,7 +432,7 @@ class Asset(AccountsController):
 					)
 					skip_row = True
 
-				if depreciation_amount > 0:
+				if flt(depreciation_amount, self.precision("gross_purchase_amount")) > 0:
 					self.append(
 						"schedules",
 						{
@@ -1281,9 +1281,11 @@ def get_straight_line_or_manual_depr_amount(asset, row):
 		)
 	# if the Depreciation Schedule is being prepared for the first time
 	else:
-		return (flt(asset.gross_purchase_amount) - flt(row.expected_value_after_useful_life)) / flt(
-			row.total_number_of_depreciations
-		)
+		return (
+			flt(asset.gross_purchase_amount)
+			- flt(asset.opening_accumulated_depreciation)
+			- flt(row.expected_value_after_useful_life)
+		) / flt(row.total_number_of_depreciations - asset.number_of_depreciations_booked)
 
 
 def get_wdv_or_dd_depr_amount(

erpnext/assets/doctype/asset/test_asset.py

@@ -569,7 +569,7 @@ class TestDepreciationMethods(AssetSetup):
 		)
 
 		self.assertEqual(asset.status, "Draft")
-		expected_schedules = [["2032-12-31", 30000.0, 77095.89], ["2033-06-06", 12904.11, 90000.0]]
+		expected_schedules = [["2032-12-31", 42904.11, 90000.0]]
 		schedules = [
 			[cstr(d.schedule_date), flt(d.depreciation_amount, 2), d.accumulated_depreciation_amount]
 			for d in asset.get("schedules")