[Minor Fix] Force toggle display Net Total field when default taxes are fetched (#15532)

* Minor fix for the problem that Net Total, Net Rate, Net Amount field would not be shown when default taxes were fetched

* Prevent net_rate from becoming NaN

* -Fixed problem that party_account_currency was not set in mapped document
-Fixed problem that discount amount was not recalculated (in mapped document)
-Fixed problem that set_dynamic_fields would work only on certain condition that led to showing Total (Company Currency) field even when using company currency

erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py

@@ -123,6 +123,7 @@ class PurchaseInvoice(BuyingController):
 	def set_missing_values(self, for_validate=False):
 		if not self.credit_to:
 			self.credit_to = get_party_account("Supplier", self.supplier, self.company)
+			self.party_account_currency = frappe.db.get_value("Account", self.credit_to, "account_currency", cache=True)
 		if not self.due_date:
 			self.due_date = get_due_date(self.posting_date, "Supplier", self.supplier, self.company,  self.bill_date)
 

erpnext/accounts/doctype/sales_invoice/sales_invoice.py

@@ -310,6 +310,7 @@ class SalesInvoice(SellingController):
 
 		if not self.debit_to:
 			self.debit_to = get_party_account("Customer", self.customer, self.company)
+			self.party_account_currency = frappe.db.get_value("Account", self.debit_to, "account_currency", cache=True)
 		if not self.due_date and self.customer:
 			self.due_date = get_due_date(self.posting_date, "Customer", self.customer, self.company)
 

erpnext/controllers/taxes_and_totals.py

@@ -70,6 +70,7 @@ class calculate_taxes_and_totals(object):
 						if item.rate_with_margin > 0 else item.rate
 
 				item.net_rate = item.rate
+				item.discount_amount = item.price_list_rate - item.rate
 				item.amount = flt(item.rate * item.qty,	item.precision("amount"))
 				item.net_amount = item.amount
 

erpnext/public/js/controllers/taxes_and_totals.js

@@ -161,7 +161,7 @@ erpnext.taxes_and_totals = erpnext.payments.extend({
 
 			if(cumulated_tax_fraction && !me.discount_amount_applied) {
 				item.net_amount = flt(item.amount / (1 + cumulated_tax_fraction));
-				item.net_rate = flt(item.net_amount / item.qty, precision("net_rate", item));
+				item.net_rate = item.qty ? flt(item.net_amount / item.qty, precision("net_rate", item)) : 0;
 
 				me.set_in_company_currency(item, ["net_rate", "net_amount"]);
 			}
@@ -521,7 +521,7 @@ erpnext.taxes_and_totals = erpnext.payments.extend({
 						item.net_amount = flt(item.net_amount + discount_amount_loss,
 							precision("net_amount", item));
 					}
-					item.net_rate = flt(item.net_amount / item.qty, precision("net_rate", item));
+					item.net_rate = item.qty ? flt(item.net_amount / item.qty, precision("net_rate", item)) : 0;
 					me.set_in_company_currency(item, ["net_rate", "net_amount"]);
 				});
 

erpnext/public/js/controllers/transaction.js

@@ -286,6 +286,7 @@ erpnext.TransactionController = erpnext.taxes_and_totals.extend({
 									me.frm.set_value("taxes", r.message.taxes);
 								}
 							},
+							() => me.set_dynamic_labels(),
 							() => me.calculate_taxes_and_totals()
 						]);
 					}
@@ -845,16 +846,10 @@ erpnext.TransactionController = erpnext.taxes_and_totals.extend({
 		this.frm.toggle_reqd("plc_conversion_rate",
 			!!(this.frm.doc.price_list_name && this.frm.doc.price_list_currency));
 
-		if(this.frm.doc_currency!==this.frm.doc.currency
-			|| this.frm.doc_currency!==this.frm.doc.price_list_currency) {
-			// reset names only when the currency is different
-
 		var company_currency = this.get_company_currency();
 		this.change_form_labels(company_currency);
 		this.change_grid_labels(company_currency);
 		this.frm.refresh_fields();
-			this.frm.doc_currency = this.frm.doc.currency;
-		}
 	},
 
 	change_form_labels: function(company_currency) {