added ordering support for text queries

Author: wpjunior

docs/guide/text-indexes.rst

@@ -43,5 +43,7 @@ Next, start a text search using :attr:`QuerySet.search_text` method::
   document.title # may be: "MongoEngine 0.9 released"
 
 
+Ordering by text score
+======================
 
-
+  objects = News.objects.search('mongo').order_by('$text_score')

mongoengine/queryset/base.py

@@ -1549,6 +1549,13 @@ def _get_order_by(self, keys):
         for key in keys:
             if not key:
                 continue
+
+            if key == '$text_score':
+                # automatically set to include text scores
+                self._include_text_scores = True
+                key_list.append(('text_score', {'$meta': "textScore"}))
+                continue
+
             direction = pymongo.ASCENDING
             if key[0] == '-':
                 direction = pymongo.DESCENDING

tests/queryset/queryset.py

@@ -2791,6 +2791,28 @@ class News(Document):
 
         self.assertTrue(isinstance(new.text_score, float))
 
+        # count
+        query = News.objects.search_text('brasil').order_by('$text_score')
+        self.assertTrue(query._include_text_scores)
+
+        self.assertEqual(query.count(), 3)
+        self.assertEqual(query._query, {'$text': {'$search': 'brasil'}})
+        cursor_args = query._cursor_args
+        self.assertEqual(
+            cursor_args['fields'], {'text_score': {'$meta': 'textScore'}})
+
+        text_scores = [i.text_score for i in query]
+        self.assertEqual(len(text_scores), 3)
+
+        self.assertTrue(text_scores[0] > text_scores[1])
+        self.assertTrue(text_scores[1] > text_scores[2])
+        max_text_score = text_scores[0]
+
+        # get item
+        item = News.objects.search_text(
+            'brasil').order_by('$text_score').first()
+        self.assertEqual(item.text_score, max_text_score)
+
     @skip_older_mongodb
     def test_distinct_handles_references_to_alias(self):
         register_connection('testdb', 'mongoenginetest2')