1 files changed, 108 insertions, 0 deletions
diff --git a/lib/ansible/vars/chain_map.py b/lib/ansible/vars/chain_map.py
new file mode 100644
index 0000000000..9221aa4d0c
--- /dev/null
+++ b/lib/ansible/vars/chain_map.py
@@ -0,0 +1,108 @@
+# (c) 2016, Ansible, Inc. <support@ansible.com>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+# Make coding more python3-ish
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from collections import MutableMapping
+
+from ansible import constants as C
+from ansible.utils.vars import merge_hash
+
+class AnsibleChainMap(MutableMapping):
+    '''
+    A variation of the ChainMap idea, which is extended here to
+    also support merging dicts values from multiple levels.
+    '''
+    def __init__(self, *args, **kwargs):
+        self._maps = [dict()]
+
+    def __str__(self):
+        return str(self.to_dict())
+
+    def __getitem__(self, k):
+        if C.DEFAULT_HASH_BEHAVIOUR == 'merge':
+            tmp = None
+            found = False
+            for m in self._maps:
+                if k in m:
+                    if isinstance(m[k], dict) and isinstance(tmp, dict):
+                        tmp = merge_hash(tmp, m[k])
+                    else:
+                        tmp = m[k]
+                    found = True
+            if found:
+                return tmp
+        else:
+            for m in reversed(self._maps):
+                if k in m:
+                    return m[k]
+        raise KeyError
+
+    def __setitem__(self, k, v):
+        '''
+        This sets the key to the value specified if it is found in any
+        mapping in the list, otherwise it is set in the default dict
+        (slot 0 in the maps list)
+        '''
+        for m in reversed(self._maps):
+            if k in m:
+                m[k] = v
+                break
+        else:
+            self._maps[0][k] = v
+
+    def __delitem__(self, k):
+        '''
+        This deletes the key in ALL maps contained within the list.
+        '''
+        for m in self._maps:
+            if k in m:
+                del m[k]
+
+    def __iter__(self):
+        for k in self.keys():
+            yield k
+
+    def __len__(self):
+        return len(self.keys())
+
+    def keys(self):
+        key_set = set()
+        for m in self._maps:
+            key_set.update(m)
+
+        return list(key_set)
+
+    def update(self, m):
+        assert isinstance(m, MutableMapping)
+        self.push(m)
+
+    def push(self, m):
+        self._maps.append(m)
+
+    def pop(self):
+        return self._maps.pop()
+
+    def copy(self):
+        new_map = AnsibleChainMap()
+        new_map._maps = self._maps[:]
+        return new_map
+
+    def to_dict(self):
+        return dict((k, self[k]) for k in self.keys())