T8541: add vyos.utils.config.set_leaf() helper

Improve config formatting for valueless leaf nodes with a new helper.
Otherwise the rendered-to-string configuration would become

  device ttyS0 {
      kernel {
      }
  }

Whereas this would be the preferred representation:

  device ttyS0 {
      kernel
  }

Co-authored-by: John Estabrook <jestabro@vyos.io>

1 files changed, 7 insertions, 0 deletions

diff --git a/python/vyos/utils/config.py b/python/vyos/utils/config.py
index 5bba69a61..1032e22dc 100644
--- a/python/vyos/utils/config.py
+++ b/python/vyos/utils/config.py
@@ -71,6 +71,8 @@ def write_saved_value(path: list, value=None, config_path: str=config_file):
     set_tags(ct, path)
 
     ct.set(path, value=value, replace=True)
+    set_leaf(ct, path)
+
     write_file(config_path, ct.to_string())
 
 def flag(l: list) -> list:
@@ -92,6 +94,11 @@ def set_tags(ct: 'ConfigTree', path: list) -> None:
         if condition:
             ct.set_tag(target)
 
+def set_leaf(ct: 'ConfigTree', path: list) -> None:
+    from vyos.xml_ref import is_leaf
+    if is_leaf(path):
+        ct.set_leaf(path, True)
+
 def parse_commands(cmds: str) -> dict:
     from re import split as re_split
     from shlex import split as shlex_split