feat: rename custom field

frappe/custom/doctype/custom_field/custom_field.js

@@ -25,6 +25,7 @@ frappe.ui.form.on("Custom Field", {
 		frm.toggle_enable("dt", frm.doc.__islocal);
 		frm.trigger("dt");
 		frm.toggle_reqd("label", !frm.doc.fieldname);
+		frm.trigger("add_rename_field");
 
 		if (frm.doc.is_system_generated) {
 			frm.dashboard.add_comment(
@@ -110,6 +111,29 @@ frappe.ui.form.on("Custom Field", {
 			frm.fields_dict["options_help"].disp_area.innerHTML = "";
 		}
 	},
+	add_rename_field(frm) {
+		frm.add_custom_button(__("Rename Fieldname"), () => {
+			frappe.prompt(
+				{
+					fieldtype: "Data",
+					label: __("Fieldname"),
+					fieldname: "fieldname",
+					reqd: 1,
+				},
+				function (data) {
+					frappe.call({
+						method: "frappe.custom.doctype.custom_field.custom_field.rename_fieldname",
+						args: {
+							custom_field: frm.doc.name,
+							fieldname: data.fieldname,
+						},
+					});
+				},
+				__("Rename Fieldname"),
+				__("Rename")
+			);
+		});
+	},
 });
 
 frappe.utils.has_special_chars = function (t) {

frappe/custom/doctype/custom_field/custom_field.py

@@ -340,3 +340,52 @@ def create_custom_fields(custom_fields: dict, ignore_validate=False, update=True
 
 	finally:
 		frappe.flags.in_create_custom_fields = False
+
+
+@frappe.whitelist()
+def rename_fieldname(custom_field: str, fieldname: str):
+	frappe.only_for("System Manager")
+
+	field: CustomField = frappe.get_doc("Custom Field", custom_field)
+	parent_doctype = field.dt
+	old_fieldname = field.fieldname
+	field.fieldname = fieldname
+	field.set_fieldname()
+	new_fieldname = field.fieldname
+
+	if field.is_system_generated:
+		frappe.throw(_("System Generated Fields can not be renamed"))
+	if frappe.db.has_column(parent_doctype, fieldname):
+		frappe.throw(_("Can not rename as fieldname {0} is already present on DocType."))
+	if old_fieldname == new_fieldname:
+		frappe.msgprint(_("Old and new fieldnames are same."), alert=True)
+		return
+
+	frappe.db.rename_column(parent_doctype, old_fieldname, new_fieldname)
+
+	# Update in DB after alter column is successful, alter column will implicitly commit, so it's
+	# best to commit change on field too to avoid any possible mismatch between two.
+	field.db_set("fieldname", field.fieldname, notify=True)
+	_update_fieldname_references(field, old_fieldname, new_fieldname)
+
+	frappe.db.commit()
+	frappe.clear_cache()
+
+
+def _update_fieldname_references(
+	field: CustomField, old_fieldname: str, new_fieldname: str
+) -> None:
+	# Passwords are stored in auth table, so column name needs to be updated there.
+	if field.fieldtype == "Password":
+		Auth = frappe.qb.Table("__Auth")
+		frappe.qb.update(Auth).set(Auth.fieldname, new_fieldname).where(
+			(Auth.doctype == field.dt) & (Auth.fieldname == old_fieldname)
+		).run()
+
+	# Update ordering reference.
+	frappe.db.set_value(
+		"Custom Field",
+		{"insert_after": old_fieldname, "dt": field.dt},
+		"insert_after",
+		new_fieldname,
+	)

frappe/custom/doctype/custom_field/test_custom_field.py

@@ -2,7 +2,11 @@
 # License: MIT. See LICENSE
 
 import frappe
-from frappe.custom.doctype.custom_field.custom_field import create_custom_fields
+from frappe.custom.doctype.custom_field.custom_field import (
+	create_custom_field,
+	create_custom_fields,
+	rename_fieldname,
+)
 from frappe.tests.utils import FrappeTestCase
 
 test_records = frappe.get_test_records("Custom Field")
@@ -81,3 +85,23 @@ class TestCustomField(FrappeTestCase):
 			# undo changes commited by DDL
 			# nosemgrep
 			frappe.db.commit()
+
+	def test_custom_field_renaming(self):
+		def gen_fieldname():
+			return "test_" + frappe.generate_hash()
+
+		field = create_custom_field("ToDo", {"label": gen_fieldname()}, is_system_generated=False)
+		old = field.fieldname
+		new = gen_fieldname()
+		data = frappe.generate_hash()
+		doc = frappe.get_doc({"doctype": "ToDo", old: data, "description": "Something"}).insert()
+
+		rename_fieldname(field.name, new)
+		field.reload()
+		self.assertEqual(field.fieldname, new)
+
+		doc = frappe.get_doc("ToDo", doc.name)  # doc.reload doesn't clear old fields.
+		self.assertEqual(doc.get(new), data)
+		self.assertFalse(doc.get(old))
+
+		field.delete()

frappe/database/database.py

@@ -1285,6 +1285,9 @@ class Database:
 		"""Get estimated max row size of any table in bytes."""
 		raise NotImplementedError
 
+	def rename_column(self, doctype: str, old_column_name: str, new_column_name: str):
+		raise NotImplementedError
+
 
 @contextmanager
 def savepoint(catch: type | tuple[type, ...] = Exception):

frappe/database/mariadb/database.py

@@ -254,6 +254,20 @@ class MariaDBDatabase(MariaDBConnectionUtil, MariaDBExceptionUtil, Database):
 		null_constraint = "NOT NULL" if not nullable else ""
 		return self.sql_ddl(f"ALTER TABLE `{table_name}` MODIFY `{column}` {type} {null_constraint}")
 
+	def rename_column(self, doctype: str, old_column_name, new_column_name):
+		current_data_type = self.get_column_type(doctype, old_column_name)
+
+		table_name = get_table_name(doctype)
+
+		frappe.db.sql_ddl(
+			f"""ALTER TABLE `{table_name}`
+				CHANGE COLUMN `{old_column_name}`
+				`{new_column_name}`
+				{current_data_type}"""
+			# ^ Mariadb requires passing current data type again even if there's no change
+			# This requirement is gone from v10.5
+		)
+
 	def create_auth_table(self):
 		self.sql_ddl(
 			"""create table if not exists `__Auth` (

frappe/database/postgres/database.py

@@ -264,6 +264,12 @@ class PostgresDatabase(PostgresExceptionUtil, Database):
 				ALTER COLUMN "{column}" {null_constraint}"""
 		)
 
+	def rename_column(self, doctype: str, old_column_name: str, new_column_name: str):
+		table_name = get_table_name(doctype)
+		frappe.db.sql_ddl(
+			f"ALTER TABLE `{table_name}` RENAME COLUMN `{old_column_name}` TO `{new_column_name}`"
+		)
+
 	def create_auth_table(self):
 		self.sql_ddl(
 			"""create table if not exists "__Auth" (