fix: (india) HSN wise report

Problem:
The previous approach for calculating tax_rate was incorrect.
```
['tax_rate'] * ['number of unique rows']
```
Joining `tabSales Taxes and Charges` was adding unnecessary rows & complexity.

Solution:
Instead of trying to get tax_rate from the main query itself, I used the get_tax_accounts's data to calculate the correct tax_rate.

Todo:
Union Territory

erpnext/regional/report/hsn_wise_summary_of_outward_supplies/hsn_wise_summary_of_outward_supplies.py

@@ -23,22 +23,29 @@ def _execute(filters=None):
 	if not filters:
 		filters = {}
 	columns = get_columns()
+	output_gst_accounts = get_output_gst_accounts(filters.company)
 
 	company_currency = erpnext.get_company_currency(filters.company)
 	item_list = get_items(filters)
 	if item_list:
-		itemised_tax, tax_columns = get_tax_accounts(item_list, columns, company_currency)
+		itemised_tax, tax_columns = get_tax_accounts(
+			item_list, columns, company_currency, output_gst_accounts
+		)
 
 	data = []
 	added_item = []
 	for d in item_list:
 		if (d.parent, d.item_code) not in added_item:
-			row = [d.gst_hsn_code, d.description, d.stock_uom, d.stock_qty, d.tax_rate or 0]
+			row = [d.gst_hsn_code, d.description, d.stock_uom, d.stock_qty]
 			total_tax = 0
+			tax_rate = 0
 			for tax in tax_columns:
 				item_tax = itemised_tax.get((d.parent, d.item_code), {}).get(tax, {})
+				if item_tax.get("is_gst_tax"):
+					tax_rate += flt(item_tax.get("tax_rate", 0))
 				total_tax += flt(item_tax.get("tax_amount", 0))
 
+			row += [tax_rate]
 			row += [d.base_net_amount + total_tax]
 			row += [d.base_net_amount]
 			for tax in tax_columns:
@@ -51,6 +58,40 @@ def _execute(filters=None):
 	return columns, data
 
 
+def get_output_gst_accounts(company):
+
+	accounts = frappe.qb.DocType("Account")
+	gst_accounts = frappe.qb.DocType("GST Account")
+
+	accounts_query = (
+		frappe.qb.from_(accounts)
+		.select(accounts.name)
+		.where((accounts.account_type == "Tax") & (accounts.root_type == "Liability"))
+	)
+
+	gst_accounts_query = (
+		frappe.qb.from_(gst_accounts)
+		.select(
+			gst_accounts.cgst_account,
+			gst_accounts.sgst_account,
+			gst_accounts.igst_account,
+			gst_accounts.utgst_account,
+			gst_accounts.cess_account,
+		)
+		.where((gst_accounts.is_reverse_charge_account == 0) & (gst_accounts.company == company))
+	)
+
+	gst_accounts_list = [
+		account for sublist in gst_accounts_query.run() for account in sublist if account
+	]
+
+	tax_accounts_list = [account[0] for account in accounts_query.run() if account]
+
+	output_tax_list = [account for account in gst_accounts_list if account in tax_accounts_list]
+
+	return output_tax_list
+
+
 def get_columns():
 	columns = [
 		{
@@ -103,40 +144,19 @@ def get_items(filters):
 		SELECT
 			`tabSales Invoice Item`.gst_hsn_code,
 			`tabSales Invoice Item`.stock_uom,
-		sum(
-			`tabSales Invoice Item`.stock_qty
-			) as stock_qty,
-		sum(
-			`tabSales Invoice Item`.base_net_amount
-			) as base_net_amount,
-		sum(
-			`tabSales Invoice Item`.base_price_list_rate
-			) as base_price_list_rate,
-
+			sum(`tabSales Invoice Item`.stock_qty) AS stock_qty,
+			sum(`tabSales Invoice Item`.base_net_amount) AS base_net_amount,
+			sum(`tabSales Invoice Item`.base_price_list_rate) AS base_price_list_rate,
 			`tabSales Invoice Item`.parent,
 			`tabSales Invoice Item`.item_code,
-			`tabGST HSN Code`.description,
-		json_extract(
-			`tabSales Taxes and Charges`.item_wise_tax_detail,
-			concat(
-					'$."', `tabSales Invoice Item`.item_code,
-					'"[0]'
-				)
-			) * count(
-					distinct `tabSales Taxes and Charges`.name
-				) as tax_rate
+			`tabGST HSN Code`.description
 		FROM
 			`tabSales Invoice`
-		INNER JOIN
-			`tabSales Invoice Item` ON `tabSales Invoice`.name = `tabSales Invoice Item`.parent
-		INNER JOIN
-			`tabGST HSN Code` ON `tabSales Invoice Item`.gst_hsn_code = `tabGST HSN Code`.name % s % s
-		LEFT JOIN
-			`tabSales Taxes and Charges` ON `tabSales Taxes and Charges`.parent = `tabSales Invoice`.name
+			INNER JOIN `tabSales Invoice Item` ON `tabSales Invoice`.name = `tabSales Invoice Item`.parent
+			INNER JOIN `tabGST HSN Code` ON `tabSales Invoice Item`.gst_hsn_code = `tabGST HSN Code`.name % s % s
 		WHERE
 			`tabSales Invoice`.docstatus = 1
-		AND
-			`tabSales Invoice Item`.gst_hsn_code is not NULL
+			AND `tabSales Invoice Item`.gst_hsn_code IS NOT NULL
 		GROUP BY
 			`tabSales Invoice Item`.parent,
 			`tabSales Invoice Item`.item_code,
@@ -158,6 +178,7 @@ def get_tax_accounts(
 	item_list,
 	columns,
 	company_currency,
+	output_gst_accounts,
 	doctype="Sales Invoice",
 	tax_doctype="Sales Taxes and Charges",
 ):
@@ -210,15 +231,25 @@ def get_tax_accounts(
 						continue
 					itemised_tax.setdefault(item_code, frappe._dict())
 					if isinstance(tax_data, list):
+						tax_rate = 0
+						is_gst_tax = 0
+						if account_head in output_gst_accounts:
+							is_gst_tax = 1
+							tax_rate = tax_data[0]
 						tax_amount = tax_data[1]
 					else:
+						tax_rate = 0
 						tax_amount = 0
 
 					for d in item_row_map.get(parent, {}).get(item_code, []):
 						item_tax_amount = tax_amount
 						if item_tax_amount:
 							itemised_tax.setdefault((parent, item_code), {})[account_head] = frappe._dict(
-								{"tax_amount": flt(item_tax_amount, tax_amount_precision)}
+								{
+									"tax_rate": flt(tax_rate, 2),
+									"is_gst_tax": is_gst_tax,
+									"tax_amount": flt(item_tax_amount, tax_amount_precision),
+								}
 							)
 			except ValueError:
 				continue