Add recursive get key from dict

The docker_config (and other data) that we have in tripleo is a complex
dict but we need a way to fetch a specific key from a larget structure.
This change adds a filter called recursive_get_key_from_dict which will
traverse all the dictionaries in a given dataset and return a list
containing all the values of the requested key.

Change-Id: I952df4d4a7700eccdb2d49a7fba271518058771a

tripleo_ansible/ansible_plugins/filter/helpers.py

@@ -29,7 +29,8 @@ class FilterModule(object):
             'haskey': self.haskey,
             'list_of_keys': self.list_of_keys,
             'container_exec_cmd': self.container_exec_cmd,
-            'get_key_from_dict': self.get_key_from_dict
+            'get_key_from_dict': self.get_key_from_dict,
+            'recursive_get_key_from_dict': self.recursive_get_key_from_dict
         }
 
     def subsort(self, dict_to_sort, attribute, null_value=0):
@@ -218,6 +219,22 @@ class FilterModule(object):
                     returned_list.append(value)
         return sorted(returned_list)
 
+    def recursive_get_key_from_dict(self, data, key):
+        """Recursively return values for keys in a dict
+
+        This filter will traverse all the dictionaries in the provided
+        dictionary and return any values for a specified key.  This is useful
+        if you have a complex dictionary containing dynamic keys but want to
+        fetch a commonly named key.
+        """
+        val = []
+        if key in data:
+            val.append(data.get(key))
+        for k, v in data.items():
+            if isinstance(v, dict):
+                val.extend(self.recursive_get_key_from_dict(v, key))
+        return val
+
     def list_or_dict_arg(self, data, cmd, key, arg):
         """Utility to build a command and its argument with list or dict data.
 

tripleo_ansible/tests/plugins/filter/test_helpers.py

@@ -367,6 +367,26 @@ class TestHelperFilters(tests_base.TestCase):
                                                 default='service')
         self.assertEqual(result, expected_list)
 
+    def test_recursive_get_key_from_dict(self):
+        data = {
+            'step': {'container': {'name': 'foo', 'image': 'bar'},
+                     'other_container': {'name': 'meh', 'image': 'baz'}
+            }
+        }
+        expected_list = ['bar', 'baz']
+        result = self.filters.recursive_get_key_from_dict(data, 'image')
+        self.assertEqual(result, expected_list)
+
+    def test_recursive_get_key_from_dict_multiple_levels(self):
+        data = {
+            'a': {'b': {'val': 1},
+                  'c': {'val': 2, 'd': {'val': 3}}
+            }
+        }
+        expected_list = [1, 2, 3]
+        result = self.filters.recursive_get_key_from_dict(data, 'val')
+        self.assertEqual(result, expected_list)
+
     def test_container_exec_cmd(self):
         data = {
             "action": "exec",