fix!: create property setters for system generated custom fields

frappe/custom/doctype/custom_field/custom_field.js

@@ -25,6 +25,27 @@ frappe.ui.form.on("Custom Field", {
 		frm.toggle_enable("dt", frm.doc.__islocal);
 		frm.trigger("dt");
 		frm.toggle_reqd("label", !frm.doc.fieldname);
+
+		if (frm.doc.is_system_generated) {
+			frm.dashboard.add_comment(
+				__(
+					"<strong>Warning:</strong> This field is system generated and may be overwritten by a future update. Modify it using {0} instead.",
+					[
+						frappe.utils.get_form_link(
+							"Customize Form",
+							"Customize Form",
+							true,
+							__("Customize Form"),
+							{
+								doc_type: frm.doc.dt,
+							}
+						),
+					]
+				),
+				"yellow",
+				true
+			);
+		}
 	},
 	dt: function (frm) {
 		if (!frm.doc.dt) {

frappe/custom/doctype/customize_form/customize_form.js

@@ -251,10 +251,23 @@ frappe.ui.form.on("Customize Form", {
 // can't delete standard fields
 frappe.ui.form.on("Customize Form Field", {
 	before_fields_remove: function (frm, doctype, name) {
-		var row = frappe.get_doc(doctype, name);
+		let row = frappe.get_doc(doctype, name);
+
+		if (row.is_system_generated) {
+			frappe.throw(
+				__(
+					"Cannot delete system generated field <strong>{0}</strong>. You can hide it instead.",
+					[__(row.label) || row.fieldname]
+				)
+			);
+		}
+
 		if (!(row.is_custom_field || row.__islocal)) {
-			frappe.msgprint(__("Cannot delete standard field. You can hide it if you want"));
-			throw "cannot delete standard field";
+			frappe.throw(
+				__("Cannot delete standard field <strong>{0}</strong>. You can hide it instead.", [
+					__(row.label) || row.fieldname,
+				])
+			);
 		}
 	},
 	fields_add: function (frm, cdt, cdn) {

frappe/custom/doctype/customize_form/customize_form.py

@@ -193,8 +193,9 @@ class CustomizeForm(Document):
 		# docfield
 		for df in self.get("fields"):
 			meta_df = meta.get("fields", {"fieldname": df.fieldname})
-			if not meta_df or meta_df[0].get("is_custom_field"):
+			if not meta_df or not is_standard_or_system_generated_field(meta_df[0]):
 				continue
+
 			self.set_property_setters_for_docfield(meta, df, meta_df)
 
 		# action and links
@@ -350,12 +351,14 @@ class CustomizeForm(Document):
 
 	def update_custom_fields(self):
 		for i, df in enumerate(self.get("fields")):
-			if df.get("is_custom_field"):
-				if not frappe.db.exists("Custom Field", {"dt": self.doc_type, "fieldname": df.fieldname}):
-					self.add_custom_field(df, i)
-					self.flags.update_db = True
-				else:
-					self.update_in_custom_field(df, i)
+			if is_standard_or_system_generated_field(df):
+				continue
+
+			if not frappe.db.exists("Custom Field", {"dt": self.doc_type, "fieldname": df.fieldname}):
+				self.add_custom_field(df, i)
+				self.flags.update_db = True
+			else:
+				self.update_in_custom_field(df, i)
 
 		self.delete_custom_fields()
 
@@ -380,7 +383,7 @@ class CustomizeForm(Document):
 	def update_in_custom_field(self, df, i):
 		meta = frappe.get_meta(self.doc_type)
 		meta_df = meta.get("fields", {"fieldname": df.fieldname})
-		if not (meta_df and meta_df[0].get("is_custom_field")):
+		if not meta_df or is_standard_or_system_generated_field(meta_df[0]):
 			# not a custom field
 			return
 
@@ -416,7 +419,7 @@ class CustomizeForm(Document):
 		}
 		for fieldname in fields_to_remove:
 			df = meta.get("fields", {"fieldname": fieldname})[0]
-			if df.get("is_custom_field"):
+			if not is_standard_or_system_generated_field(df):
 				frappe.delete_doc("Custom Field", df.name)
 
 	def make_property_setter(
@@ -561,6 +564,10 @@ def reset_customization(doctype):
 	frappe.clear_cache(doctype=doctype)
 
 
+def is_standard_or_system_generated_field(df):
+	return not df.get("is_custom_field") or df.get("is_system_generated")
+
+
 doctype_properties = {
 	"search_fields": "Data",
 	"title_field": "Data",

frappe/custom/doctype/customize_form/test_customize_form.py

@@ -403,3 +403,25 @@ class TestCustomizeForm(FrappeTestCase):
 
 		with self.assertRaises(frappe.ValidationError):
 			d.run_method("save_customization")
+
+	def test_system_generated_fields(self):
+		doctype = "Event"
+		custom_field_name = "test_custom_field"
+
+		custom_field = frappe.get_doc("Custom Field", {"dt": doctype, "fieldname": custom_field_name})
+		custom_field.is_system_generated = 1
+		custom_field.save()
+
+		d = self.get_customize_form(doctype)
+		custom_field = d.getone("fields", {"fieldname": custom_field_name})
+		custom_field.description = "Test Description"
+		d.run_method("save_customization")
+
+		property_setter_filters = {
+			"doc_type": doctype,
+			"field_name": custom_field_name,
+			"property": "description",
+		}
+		self.assertEqual(
+			frappe.db.get_value("Property Setter", property_setter_filters, "value"), "Test Description"
+		)