From 6ab0046e9c6d311c5496347a37770f30ffd59f52 Mon Sep 17 00:00:00 2001
From: Ankush Menat <me@ankush.dev>
Date: Tue, 10 May 2022 12:32:56 +0530
Subject: [PATCH] fix: consider previous balance is missing

Also remove `total`, total of total is a meaningless value.
---
 .../report/stock_analytics/stock_analytics.py | 52 ++++++++++++++++---
 .../stock_analytics/test_stock_analytics.py   | 12 +++++
 2 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/erpnext/stock/report/stock_analytics/stock_analytics.py b/erpnext/stock/report/stock_analytics/stock_analytics.py
index da0776b9a8..77faa1f679 100644
--- a/erpnext/stock/report/stock_analytics/stock_analytics.py
+++ b/erpnext/stock/report/stock_analytics/stock_analytics.py
@@ -1,6 +1,7 @@
 # Copyright (c) 2013, Frappe Technologies Pvt. Ltd. and contributors
 # For license information, please see license.txt
 import datetime
+from typing import List
 
 import frappe
 from frappe import _, scrub
@@ -148,11 +149,19 @@ def get_periodic_data(entry, filters):
 	                        - Warehouse A : bal_qty/value
 	                        - Warehouse B : bal_qty/value
 	"""
+
+	expected_ranges = get_period_date_ranges(filters)
+	expected_periods = []
+	for _start_date, end_date in expected_ranges:
+		expected_periods.append(get_period(end_date, filters))
+
 	periodic_data = {}
 	for d in entry:
 		period = get_period(d.posting_date, filters)
 		bal_qty = 0
 
+		fill_intermediate_periods(periodic_data, d.item_code, period, expected_periods)
+
 		# if period against item does not exist yet, instantiate it
 		# insert existing balance dict against period, and add/subtract to it
 		if periodic_data.get(d.item_code) and not periodic_data.get(d.item_code).get(period):
@@ -186,6 +195,36 @@ def get_periodic_data(entry, filters):
 	return periodic_data
 
 
+def fill_intermediate_periods(
+	periodic_data, item_code: str, current_period: str, all_periods: List[str]
+) -> None:
+	"""There might be intermediate periods where no stock ledger entry exists, copy previous previous data.
+
+	Previous data is ONLY copied if period falls in report range and before period being processed currently.
+
+	args:
+	        current_period: process till this period (exclusive)
+	        all_periods: all periods expected in report via filters
+	        periodic_data: report's periodic data
+	        item_code: item_code being processed
+	"""
+
+	previous_period_data = None
+	for period in all_periods:
+		if period == current_period:
+			return
+
+		if (
+			periodic_data.get(item_code)
+			and not periodic_data.get(item_code).get(period)
+			and previous_period_data
+		):
+			# This period should exist since it's in report range, assign previous period data
+			periodic_data[item_code][period] = previous_period_data.copy()
+
+		previous_period_data = periodic_data.get(item_code, {}).get(period)
+
+
 def get_data(filters):
 	data = []
 	items = get_items(filters)
@@ -202,14 +241,15 @@ def get_data(filters):
 			"uom": item_data.stock_uom,
 			"brand": item_data.brand,
 		}
-		total = 0
-		for dummy, end_date in ranges:
+		previous_period_value = 0.0
+		for _start_date, end_date in ranges:
 			period = get_period(end_date, filters)
 			period_data = periodic_data.get(item_data.name, {}).get(period)
-			amount = sum(period_data.values()) if period_data else 0
-			row[scrub(period)] = amount
-			total += amount
-		row["total"] = total
+			if period_data:
+				row[scrub(period)] = previous_period_value = sum(period_data.values())
+			else:
+				row[scrub(period)] = previous_period_value
+
 		data.append(row)
 
 	return data
diff --git a/erpnext/stock/report/stock_analytics/test_stock_analytics.py b/erpnext/stock/report/stock_analytics/test_stock_analytics.py
index d9f10e5455..dd8f8d8038 100644
--- a/erpnext/stock/report/stock_analytics/test_stock_analytics.py
+++ b/erpnext/stock/report/stock_analytics/test_stock_analytics.py
@@ -102,3 +102,15 @@ class TestStockAnalyticsReport(FrappeTestCase):
 			(20, add_to_date(today, months=3).replace(day=15)),
 		]
 		self.assert_single_item_report(movement, [100, 50, 50, 70])
+
+	def test_multi_month_missings(self):
+		today = getdate()
+		movement = [
+			(100, add_to_date(today, months=0).replace(day=15)),
+			(-50, add_to_date(today, months=1).replace(day=15)),
+			# Skip a month
+			(20, add_to_date(today, months=3).replace(day=15)),
+			# Skip another month
+			(-10, add_to_date(today, months=5).replace(day=15)),
+		]
+		self.assert_single_item_report(movement, [100, 50, 50, 70, 70, 60])