fix for fields names at sales invoice return payments and verifying the payment amount (#15245)

* fix for payments field names in sales invoice return

* add verification for payment amount at sales invoice return

adding verification to be sure the payment amount is negative at sales
invoice return

* correction for precision field name

erpnext/accounts/doctype/sales_invoice/sales_invoice.py

@@ -112,6 +112,11 @@ class SalesInvoice(SellingController):
 		self.set_status()
 		if self.is_pos and not self.is_return:
 			self.verify_payment_amount_is_positive()
+
+		#validate amount in mode of payments for returned invoices for pos must be negative
+		if self.is_pos and self.is_return:
+			self.verify_payment_amount_is_negative()
+			
 		if self.redeem_loyalty_points and self.loyalty_program and self.loyalty_points:
 			validate_loyalty_points(self, self.loyalty_points)
 
@@ -971,6 +976,11 @@ class SalesInvoice(SellingController):
 			if entry.amount < 0:
 				frappe.throw(_("Row #{0} (Payment Table): Amount must be positive").format(entry.idx))
 
+	def verify_payment_amount_is_negative(self):			
+		for entry in self.payments:
+    			if entry.amount > 0:
+				frappe.throw(_("Row #{0} (Payment Table): Amount must be negative").format(entry.idx))				
+
 	# collection of the loyalty points, create the ledger entry for that.
 	def make_loyalty_point_entry(self):
 		returned_amount = self.get_returned_amount()

erpnext/controllers/sales_and_purchase_return.py

@@ -232,8 +232,8 @@ def make_return_doc(doctype, source_name, target_doc=None):
 					doc.append('payments', {
 						'mode_of_payment': data.mode_of_payment,
 						'type': data.type,
-						'paid_amount': -1 * paid_amount,
-						'base_paid_amount': -1 * base_paid_amount
+						'amount': -1 * paid_amount,
+						'base_amount': -1 * base_paid_amount
 					})
 			elif doc.doctype == 'Purchase Invoice':
 				doc.paid_amount = -1 * source.paid_amount