[hook] added before_change hook to trigger email_alerts before db_set

frappe/model/base_document.py

@@ -381,6 +381,9 @@ class BaseDocument(object):
 			self.set("modified", now())
 			self.set("modified_by", frappe.session.user)
 
+		# to trigger email alert on value change
+		self.run_method('before_change')
+
 		frappe.db.set_value(self.doctype, self.name, fieldname, value,
 			self.modified, self.modified_by, update_modified=update_modified)
 

frappe/model/document.py

@@ -681,6 +681,7 @@ class Document(BaseDocument):
 		def _evaluate_alert(alert):
 			if not alert.name in self.flags.email_alerts_executed:
 				evaluate_alert(self, alert.name, alert.event)
+				self.flags.email_alerts_executed.append(alert.name)
 
 		event_map = {
 			"on_update": "Save",
@@ -692,6 +693,7 @@ class Document(BaseDocument):
 		if not self.flags.in_insert:
 			# value change is not applicable in insert
 			event_map['validate'] = 'Value Change'
+			event_map['before_change'] = 'Value Change'
 
 		for alert in self.flags.email_alerts:
 			event = event_map.get(method, None)