added .keys(), items(), values(), corrected __contains__

There was a huge problem with 3.4 and 3.3 as the OrderedDict
does not define a __contains__ and the implementation based on
the one by Ngo would not work with merge keys defining keys
that later were in the main dict (which should override).
Fix was to add the merge key info at the point the dict
has been completely created, thus restricting __contains__
automatically to the dict itself (and not test subkeys)

1 files changed, 4 insertions, 2 deletions

diff --git a/constructor.py b/constructor.py
index c86989a..a07a8e3 100644
--- a/constructor.py
+++ b/constructor.py
@@ -941,8 +941,6 @@ class RoundTripConstructor(SafeConstructor):
                 "expected a mapping node, but found %s" % node.id,
                 node.start_mark)
         merge_map = self.flatten_mapping(node)
-        if merge_map:
-            maptyp.add_yaml_merge(merge_map)
         # mapping = {}
         if node.comment:
             maptyp._yaml_add_comment(node.comment[:2])
@@ -981,6 +979,10 @@ class RoundTripConstructor(SafeConstructor):
                 key, [key_node.start_mark.line, key_node.start_mark.column,
                       value_node.start_mark.line, value_node.start_mark.column])
             maptyp[key] = value
+        # do this last, or <<: before a key will prevent insertion in instances
+        # of collections.OrderedDict (as they have no __contains__
+        if merge_map:
+            maptyp.add_yaml_merge(merge_map)
 
     def construct_setting(self, node, typ, deep=False):
         if not isinstance(node, MappingNode):