T8980: add util get_saved_config_tree

Add util for commonly used retrieval of ConfigTree of the saved config.

2 files changed, 27 insertions, 0 deletions

diff --git a/python/vyos/configtree.py b/python/vyos/configtree.py
index 9c5d69ad1..24b3252fd 100644
--- a/python/vyos/configtree.py
+++ b/python/vyos/configtree.py
@@ -19,6 +19,8 @@ import logging
 
 from ctypes import cdll, c_char_p, c_void_p, c_int, c_bool
 from typing import TYPE_CHECKING
+from pathlib import Path
+
 
 # https://peps.python.org/pep-0484/#forward-references
 # for type 'ConfigDict'
@@ -265,6 +267,19 @@ class ConfigTree:
         if self.__migration:
             self.migration_log = logging.getLogger('vyos.migrate')
 
+    @classmethod
+    def load_file(cls, location):
+        # pylint: disable=raise-missing-from
+        config_file = Path(location)
+        if not config_file.exists():
+            raise ConfigTreeError(f'Missing config file at {location}')
+        try:
+            config_tree = cls(config_file.read_text())
+        except (OSError, ValueError, TypeError) as e:
+            raise ConfigTreeError(f'Corrupted config file at {location}: {e}')
+
+        return config_tree
+
     def __del__(self):
         if self.__config is not None:
             self.__destroy(self.__config)
diff --git a/python/vyos/utils/config.py b/python/vyos/utils/config.py
index 1032e22dc..004d64bbd 100644
--- a/python/vyos/utils/config.py
+++ b/python/vyos/utils/config.py
@@ -75,6 +75,18 @@ def write_saved_value(path: list, value=None, config_path: str=config_file):
 
     write_file(config_path, ct.to_string())
 
+
+def get_saved_config_tree() -> 'ConfigTree':
+    # pylint: disable=import-outside-toplevel
+    """Return config tree of saved config.
+
+    Raises ConfigTreeError.
+    """
+    from vyos.configtree import ConfigTree
+
+    return ConfigTree.load_file(config_file)
+
+
 def flag(l: list) -> list:
     res = [l[0:i] for i,_ in enumerate(l, start=1)]
     return res