[utils] Added utils.merge_list #56

docs/source/general/basics.rst

@@ -275,11 +275,13 @@ refactor the previous code as follows:
     }
     router2 = OpenWrt(router2_config, templates=[dhcp_template])
 
-The function used under the hood to merge dictionaries and lists
-is ``netjsonconfig.utils.merge_config``:
+The functions used under the hood to merge configurations and templates
+are ``netjsonconfig.utils.merge_config`` and ``netjsonconfig.utils.merge_list``:
 
 .. autofunction:: netjsonconfig.utils.merge_config
 
+.. autofunction:: netjsonconfig.utils.merge_list
+
 .. _multiple_templates:
 
 Multiple template inheritance

netjsonconfig/utils.py

@@ -13,8 +13,8 @@ def merge_config(template, config):
 
     * simple values (eg: ``str``, ``int``, ``float``, ecc) in ``config`` will
       overwrite the ones in ``template``
-    * values of type ``list`` in both ``config`` and ``template`` will be summed
-      in order to create a list which contains elements of both
+    * values of type ``list`` in both ``config`` and ``template`` will be
+      merged using to the ``merge_list`` function
     * values of type ``dict`` will be merged recursively
 
     :param template: template ``dict``
@@ -27,12 +27,43 @@ def merge_config(template, config):
             node = result.get(key, {})
             result[key] = merge_config(node, value)
         elif isinstance(value, list) and isinstance(result.get(key), list):
-            result[key] = deepcopy(result[key]) + deepcopy(value)
+            result[key] = merge_list(result[key], value)
         else:
             result[key] = value
     return result
 
 
+def merge_list(list1, list2):
+    """
+    Merges ``list2`` on top of ``list1``.
+
+    If both lists contain dictionaries which have keys like
+    ``name`` or ``id`` of equal values, those dicts are merged
+    (dicts in ``list2`` will override dicts in ``list1``).
+    The remaining elements will be summed in order to create a list
+    which contains elements of both lists.
+
+    :param list1: list from template
+    :param list2: list from config
+    :returns: merged ``list``
+    """
+    dict_map = {'list1': OrderedDict(), 'list2': OrderedDict()}
+    counter = 1
+    for list_ in [list1, list2]:
+        container = dict_map['list{0}'.format(counter)]
+        for el in list_:
+            if isinstance(el, dict) and 'name' in el:
+                key = el['name']
+            elif isinstance(el, dict) and 'id' in el:
+                key = el['id']
+            else:
+                key = id(el)
+            container[key] = deepcopy(el)
+        counter += 1
+    merged = merge_config(dict_map['list1'], dict_map['list2'])
+    return list(merged.values())
+
+
 def sorted_dict(dictionary):
     return OrderedDict(sorted(dictionary.items()))
 

tests/test_utils.py

@@ -1,6 +1,6 @@
 import unittest
 
-from netjsonconfig.utils import evaluate_vars, merge_config
+from netjsonconfig.utils import evaluate_vars, merge_config, merge_list
 
 
 class TestUtils(unittest.TestCase):
@@ -168,3 +168,21 @@ def test_evaluate_vars_immersed(self):
 
     def test_evaluate_vars_one_char(self):
         self.assertEqual(evaluate_vars('{{ a }}', {'a': 'letter-A'}), 'letter-A')
+
+    def test_merge_list_override(self):
+        template = [{"name": "test1", "tx": 1}]
+        config = [{"name": "test1", "tx": 2}]
+        result = merge_list(template, config)
+        self.assertEqual(result, config)
+
+    def test_merge_list_union_and_override(self):
+        template = [{"id": "test1", "a": "a"}]
+        config = [
+            {"id": "test1", "a": "0", "b": "b"},
+            {"id": "test2", "c": "c"}
+        ]
+        result = merge_list(template, config)
+        self.assertEqual(result, [
+            {"id": "test1", "a": "0", "b": "b"},
+            {"id": "test2", "c": "c"}
+        ])