PYTHON-1821 Preserve field ordering when iterating over RawBSONDocument

instances

Author: prashantmital

doc/changelog.rst

@@ -101,6 +101,8 @@ Changes in Version 3.8.0.dev0
 - :class:`~bson.raw_bson.RawBSONDocument` now validates that the ``bson_bytes``
   passed in represent a single bson document. Earlier versions would mistakenly
   accept multiple bson documents.
+- Iterating over a :class:`~bson.raw_bson.RawBSONDocument` now maintains the
+  same field order of the underlying raw BSON document.
 
 Issues Resolved
 ...............

test/test_raw_bson.py

@@ -20,6 +20,7 @@
 from bson.codec_options import CodecOptions
 from bson.errors import InvalidBSON
 from bson.raw_bson import RawBSONDocument
+from bson.son import SON
 from test import client_context, unittest
 
 
@@ -157,3 +158,10 @@ def test_write_response_raw_bson(self):
         coll.delete_many(self.document)
         coll.update_one(self.document, {'$set': {'a': 'b'}}, upsert=True)
         coll.update_many(self.document, {'$set': {'b': 'c'}})
+
+    def test_preserve_key_ordering(self):
+        keyvaluepairs = [('a', 1), ('b', 2), ('c', 3),]
+        rawdoc = RawBSONDocument(BSON.encode(SON(keyvaluepairs)))
+
+        for rkey, elt in zip(rawdoc, keyvaluepairs):
+            self.assertEqual(rkey, elt[0])