vyos.configtree: T6620: allow list_nodes() to work on non-existent paths

and return an empty list in that case
(handy for migration scripts and the like)

python/vyos/configtree.py

@@ -1,5 +1,5 @@
 # configtree -- a standalone VyOS config file manipulation library (Python bindings)
-# Copyright (C) 2018-2022 VyOS maintainers and contributors
+# Copyright (C) 2018-2024 VyOS maintainers and contributors
 #
 # This library is free software; you can redistribute it and/or modify it under the terms of
 # the GNU Lesser General Public License as published by the Free Software Foundation;
@@ -290,15 +290,18 @@ def exists(self, path):
         else:
             return True
 
-    def list_nodes(self, path):
+    def list_nodes(self, path, path_must_exist=True):
         check_path(path)
         path_str = " ".join(map(str, path)).encode()
 
         res_json = self.__list_nodes(self.__config, path_str).decode()
         res = json.loads(res_json)
 
         if res is None:
-            raise ConfigTreeError("Path [{}] doesn't exist".format(path_str))
+            if path_must_exist:
+                raise ConfigTreeError("Path [{}] doesn't exist".format(path_str))
+            else:
+                return []
         else:
             return res
 

src/migration-scripts/openvpn/1-to-2

@@ -20,12 +20,8 @@
 from vyos.configtree import ConfigTree
 
 def migrate(config: ConfigTree) -> None:
-    if not config.exists(['interfaces', 'openvpn']):
-        # Nothing to do
-        return
-
-    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'])
-    for	i in ovpn_intfs:
+    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'], path_must_exist=False)
+    for i in ovpn_intfs:
         # Remove 'encryption cipher' and add this value to 'encryption ncp-ciphers'
         # for server and client mode.
         # Site-to-site mode still can use --cipher option

src/migration-scripts/openvpn/2-to-3

@@ -20,12 +20,8 @@
 from vyos.configtree import ConfigTree
 
 def migrate(config: ConfigTree) -> None:
-    if not config.exists(['interfaces', 'openvpn']):
-        # Nothing to do
-        return
-
-    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'])
-    for	i in ovpn_intfs:
+    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'], path_must_exist=False)
+    for i in ovpn_intfs:
         mode = config.return_value(['interfaces', 'openvpn', i, 'mode'])
         if mode != 'server':
             # If it's a client or a site-to-site OpenVPN interface,

src/migration-scripts/openvpn/3-to-4

@@ -18,11 +18,7 @@
 from vyos.configtree import ConfigTree
 
 def migrate(config: ConfigTree) -> None:
-    if not config.exists(['interfaces', 'openvpn']):
-        # Nothing to do
-        return
-
-    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'])
+    ovpn_intfs = config.list_nodes(['interfaces', 'openvpn'], path_must_exist=False)
     for i in ovpn_intfs:
         #Rename 'encryption ncp-ciphers' with 'encryption data-ciphers'
         ncp_cipher_path = ['interfaces', 'openvpn', i, 'encryption', 'ncp-ciphers']