feat: validate training event period

erpnext/hr/doctype/training_event/training_event.py

@@ -5,9 +5,19 @@
 from __future__ import unicode_literals
 import frappe
 from frappe.model.document import Document
+from frappe import _
+from frappe.utils import time_diff_in_seconds
 from erpnext.hr.doctype.employee.employee import get_employee_emails
 
 class TrainingEvent(Document):
 	def validate(self):
+		self.set_employee_emails()
+		self.validate_period()
+
+	def set_employee_emails(self):
 		self.employee_emails = ', '.join(get_employee_emails([d.employee
 			for d in self.employees]))
+
+	def validate_period(self):
+		if time_diff_in_seconds(self.end_time, self.start_time) <= 0:
+			frappe.throw(_('End time cannot be before start time'))