refactor(Timesheet): move validation to Timesheet Detail

erpnext/projects/doctype/timesheet/timesheet.py

@@ -143,15 +143,8 @@ def on_submit(self):
 		self.update_task_and_project()
 
 	def validate_mandatory_fields(self):
-		for data in self.time_logs:
-			if not data.from_time and not data.to_time:
-				frappe.throw(_("Row {0}: From Time and To Time is mandatory.").format(data.idx))
-
-			if not data.activity_type and self.employee:
-				frappe.throw(_("Row {0}: Activity Type is mandatory.").format(data.idx))
-
-			if flt(data.hours) == 0.0:
-				frappe.throw(_("Row {0}: Hours value must be greater than zero.").format(data.idx))
+		for time_log in self.time_logs:
+			time_log.validate_mandatory_fields(needs_activity_type=bool(self.employee))
 
 	def update_task_and_project(self):
 		tasks, projects = [], []

erpnext/projects/doctype/timesheet_detail/timesheet_detail.py

@@ -123,3 +123,25 @@ def validate_billing_hours(self):
 				indicator="orange",
 				alert=True,
 			)
+
+	def validate_mandatory_fields(self, needs_activity_type: bool = False):
+		for fieldname in ("from_time", "to_time"):
+			if not self.get(fieldname):
+				frappe.throw(
+					_("Row {0}: Please set {1}.").format(
+						self.idx,
+						_(self.meta.get_label(fieldname)),
+					)
+				)
+
+		if needs_activity_type and not self.activity_type:
+			frappe.throw(
+				_("Row {0}: please set {1}.").format(self.idx, _(self.meta.get_label("activity_type")))
+			)
+
+		if flt(self.hours) == 0.0:
+			frappe.throw(
+				_("Row {0}: The value of the field {1} cannot be 0.").format(
+					self.idx, _(self.meta.get_label("hours"))
+				)
+			)