validation to check for possible duplicate payment terms

erpnext/accounts/doctype/payment_terms_template/payment_terms_template.py

@@ -14,6 +14,7 @@ class PaymentTermsTemplate(Document):
 	def validate(self):
 		self.validate_invoice_portion()
 		self.validate_credit_days()
+		self.check_duplicate_terms()
 
 	def validate_invoice_portion(self):
 		total_portion = 0
@@ -28,3 +29,14 @@ class PaymentTermsTemplate(Document):
 			if term.credit_days < 0:
 				frappe.msgprint(_('Credit Days cannot be a negative number'), raise_exception=1, indicator='red')
 
+	def check_duplicate_terms(self):
+		terms = []
+		for term in self.terms:
+			term_info = (term.credit_days, term.due_date_based_on)
+			if term_info in terms:
+				frappe.msgprint(
+					_('The Payment Term at row {0} is possibly a duplicate.').format(term.idx),
+					raise_exception=1, indicator='red'
+				)
+			else:
+				terms.append(term_info)

erpnext/accounts/doctype/payment_terms_template/test_payment_terms_template.py

@@ -46,4 +46,27 @@ class TestPaymentTermsTemplate(unittest.TestCase):
 			}]
 		})
 
-		self.assertRaises(frappe.ValidationError, template.insert)
+		self.assertRaises(frappe.ValidationError, template.insert)
+
+	def test_duplicate_terms(self):
+		template = frappe.get_doc({
+			'doctype': 'Payment Terms Template',
+			'template_name': '_Test Payment Terms Template For Test',
+			'terms': [
+				{
+					'doctype': 'Payment Terms Template Detail',
+					'invoice_portion': 50.00,
+					'credit_days_based_on': 'Day(s) after invoice date',
+					'credit_days': 30
+				},
+				{
+					'doctype': 'Payment Terms Template Detail',
+					'invoice_portion': 50.00,
+					'credit_days_based_on': 'Day(s) after invoice date',
+					'credit_days': 30
+				}
+
+			]
+		})
+
+		self.assertRaises(frappe.ValidationError, template.insert)

erpnext/accounts/doctype/purchase_invoice/test_purchase_invoice.py

@@ -645,6 +645,13 @@ class TestPurchaseInvoice(unittest.TestCase):
 
 		self.assertTrue(pi.get('payment_schedule'))
 
+	def test_duplicate_due_date_in_terms(self):
+		pi = make_purchase_invoice(do_not_save=1)
+		pi.append('payment_schedule', dict(due_date='2017-01-01', invoice_portion=50.00, payment_amount=50))
+		pi.append('payment_schedule', dict(due_date='2017-01-01', invoice_portion=50.00, payment_amount=50))
+
+		self.assertRaises(frappe.ValidationError, pi.insert)
+
 
 def unlink_payment_on_cancel_of_invoice(enable=1):
 	accounts_settings = frappe.get_doc("Accounts Settings")

erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py

@@ -1361,6 +1361,13 @@ class TestSalesInvoice(unittest.TestCase):
 		si.insert()
 		self.assertTrue(si.get('payment_schedule'))
 
+	def test_duplicate_due_date_in_terms(self):
+		si = create_sales_invoice(do_not_save=1)
+		si.append('payment_schedule', dict(due_date='2017-01-01', invoice_portion=50.00, payment_amount=50))
+		si.append('payment_schedule', dict(due_date='2017-01-01', invoice_portion=50.00, payment_amount=50))
+
+		self.assertRaises(frappe.ValidationError, si.insert)
+
 
 def create_sales_invoice(**args):
 	si = frappe.new_doc("Sales Invoice")

erpnext/controllers/accounts_controller.py

@@ -648,12 +648,15 @@ class AccountsController(TransactionBase):
 		self.validate_payment_schedule_amount()
 
 	def validate_payment_schedule_dates(self):
+		dates = []
 		if self.due_date and getdate(self.due_date) < getdate(self.posting_date):
 			frappe.throw(_("Due Date cannot be before posting date"))
 
 		for d in self.get("payment_schedule"):
 			if getdate(d.due_date) < getdate(self.posting_date):
 				frappe.throw(_("Row {0}: Due Date cannot be before posting date").format(d.idx))
+			elif d.due_date in dates:
+				frappe.throw(_("Row {0}: Duplicate due date found").format(d.idx))
 
 	def validate_payment_schedule_amount(self):
 		total = 0