vyos: configdict: add dict_merge function

Merge two dictionaries. Only keys which are not present in destination will
be copied from source, anything else will be kept untouched. Function will
return a new dict which has the merged key/value pairs.

Before:
{'device': {'usb0b2.4p1.0': {'speed': '9600'},
            'usb0b2.4p1.1': {'data-bits': '8',
                             'parity': 'none',
                             'speed': '115200',
                             'stop-bits': '2'}}}

After:
{'device': {'usb0b2.4p1.0': {'data-bits': '8',
                             'parity': 'none',
                             'speed': '9600',
                             'stop-bits': '1'},
            'usb0b2.4p1.1': {'data-bits': '8',
                             'parity': 'none',
                             'speed': '115200',
                             'stop-bits': '2'}}}

1 files changed, 13 insertions, 0 deletions

diff --git a/python/vyos/configdict.py b/python/vyos/configdict.py
index 4708d3b50..973fbdd8b 100644
--- a/python/vyos/configdict.py
+++ b/python/vyos/configdict.py
@@ -87,6 +87,19 @@ def retrieve_config(path_hash, base_path, config):
     return config_hash
 
 
+def dict_merge(source, destination):
+    """ Merge two dictionaries. Only keys which are not present in destination
+    will be copied from source, anything else will be kept untouched. Function
+    will return a new dict which has the merged key/value pairs. """
+    from copy import deepcopy
+    tmp = deepcopy(destination)
+
+    for key, value in source.items():
+        if key not in tmp.keys():
+            tmp[key] = value
+
+    return tmp
+
 def list_diff(first, second):
     """
     Diff two dictionaries and return only unique items