Handle namespacing issues.

Move from using the inbuilt type names as module names
which is a bad thing to use it appears due to naming conflicts
in the __init__ module and reduce the chances of these conflicts
by enforcing a m_ prefix for merging modules.

1 files changed, 50 insertions, 0 deletions

diff --git a/cloudinit/mergers/m_list.py b/cloudinit/mergers/m_list.py
new file mode 100644
index 00000000..a56ff007
--- /dev/null
+++ b/cloudinit/mergers/m_list.py
@@ -0,0 +1,50 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+class Merger(object):
+    def __init__(self, merger, opts):
+        self._merger = merger
+        self._discard_non = 'discard_non_list' in opts
+        self._extend = 'extend' in opts
+
+    def _on_tuple(self, value, merge_with):
+        return self._on_list(list(value), merge_with)
+
+    # On encountering a list or tuple type this action will be applied
+    # a new list will be returned, if the value to merge with is itself
+    # a list and we have been told to 'extend', then the value here will
+    # be extended with the other list. If in 'extend' mode then we will
+    # attempt to merge instead, which means that values from the list
+    # to merge with will replace values in te original list (they will
+    # also be merged recursively).
+    #
+    # If the value to merge with is not a list, and we are set to discared
+    # then no modifications will take place, otherwise we will just append
+    # the value to merge with onto the end of our own list.
+    def _on_list(self, value, merge_with):
+        new_value = list(value)
+        if isinstance(merge_with, (tuple, list)):
+            if self._extend:
+                new_value.extend(merge_with)
+            else:
+                return new_value
+        else:
+            if not self._discard_non:
+                new_value.append(merge_with)
+        return new_value