fix(Virtual DocType): don't call db get_value in link field validation (

#23620)

* fix(Virtual DocType): use get_doc to validate link field instead of db get_value

* refactor: use is_virtual_doctype util & always return a dict

(cherry picked from commit cfc781e)

frappe/client.py

@@ -10,6 +10,7 @@
 from frappe import _
 from frappe.desk.reportview import validate_args
 from frappe.model.db_query import check_parent_permission
+from frappe.model.utils import is_virtual_doctype
 from frappe.utils import get_safe_filters
 
 if TYPE_CHECKING:
@@ -435,6 +436,18 @@ def validate_link(doctype: str, docname: str, fields=None):
 		)
 
 	values = frappe._dict()
+
+	if is_virtual_doctype(doctype):
+		try:
+			frappe.get_doc(doctype, docname)
+			values.name = docname
+		except frappe.DoesNotExistError:
+			frappe.clear_last_message()
+			frappe.msgprint(
+				_("Document {0} {1} does not exist").format(frappe.bold(doctype), frappe.bold(docname)),
+			)
+		return values
+
 	values.name = frappe.db.get_value(doctype, docname, cache=True)
 
 	fields = frappe.parse_json(fields)