feat: Validate field name conflicts in DocType.validate

# Conflicts:
#	frappe/core/doctype/doctype/doctype.py

(cherry picked from commit c652c7b7f5)

frappe/core/doctype/doctype/doctype.py

@@ -70,6 +70,7 @@ class DocType(Document):
 		validate_series(self)
 		self.validate_document_type()
 		validate_fields(self)
+		self.validate_field_name_conflicts()
 
 		if not self.istable:
 			validate_permissions(self)
@@ -89,6 +90,39 @@ class DocType(Document):
 		if self.default_print_format and not self.custom:
 			frappe.throw(_('Standard DocType cannot have default print format, use Customize Form'))
 
+		if frappe.conf.get('developer_mode'):
+			self.owner = 'Administrator'
+			self.modified_by = 'Administrator'
+
+	def validate_field_name_conflicts(self):
+		"""Check if field names dont conflict with controller properties and methods"""
+		from frappe.model.base_document import get_controller
+
+		controller = get_controller(self.name)
+		available_objects = {x for x in dir(controller) if isinstance(x, str)}
+		property_set = {
+			x for x in available_objects if isinstance(getattr(controller, x, None), property)
+		}
+		method_set = {
+			x for x in available_objects if x not in property_set and callable(getattr(controller, x, None))
+		}
+
+		for docfield in self.get("fields") or []:
+			conflict_type = ""
+			field = docfield.fieldname
+			field_label = docfield.label or docfield.fieldname
+
+			if docfield.fieldname in method_set:
+				conflict_type = "controller method"
+			if docfield.fieldname in property_set:
+				conflict_type = "class property"
+
+			if conflict_type:
+				frappe.throw(
+					_("Fieldname '{0}' conflicting with a {1} of the name {2} in {3}")
+						.format(field_label, conflict_type, field, self.name)
+				)
+
 	def after_insert(self):
 		# clear user cache so that on the next reload this doctype is included in boot
 		clear_user_cache(frappe.session.user)