Make sure DocType objects can correctly pickle and unpickle

Fixes #128, thanks brizzbane for the report!

elasticsearch_dsl/document.py

@@ -96,6 +96,14 @@ def __init__(self, meta=None, **kwargs):
 
         super(DocType, self).__init__(**kwargs)
 
+    def __getstate__(self):
+        return (self._d_, self.meta._d_)
+
+    def __setstate__(self, state):
+        data, meta = state
+        super(AttrDict, self).__setattr__('_d_', data)
+        super(AttrDict, self).__setattr__('meta', ResultMeta(meta))
+
     def __getattr__(self, name):
         if name.startswith('_') and name[1:] in META_FIELDS:
             return getattr(self.meta, name[1:])

test_elasticsearch_dsl/test_document.py

@@ -1,3 +1,4 @@
+import pickle
 from hashlib import md5
 from datetime import datetime
 
@@ -28,6 +29,16 @@ class MyMultiSubDoc(MyDoc2, MySubDoc):
 class DocWithNested(document.DocType):
     comments = field.Nested(properties={'title': field.String()})
 
+def test_doc_type_can_be_correctly_pickled():
+    d = MyDoc(title='Hello World!', meta={'id': 42})
+    s = pickle.dumps(d)
+
+    d2 = pickle.loads(s)
+
+    assert d2 == d
+    assert 42 == d2.meta.id
+    assert 'Hello World!' == d2.title
+
 def test_meta_is_accessible_even_on_empty_doc():
     d = MyDoc()
     d.meta