Improve Queryset.get to avoid confusing message in case multiple match are found

docs/changelog.rst

@@ -7,6 +7,7 @@ Development
 ===========
 - (Fill this out as you fix issues and develop your features).
 - Add Mongo 4.0 to Travis
+- Improve Queryset.get to avoid confusing MultipleObjectsReturned message in case multiple match are found #630
 - Fixed a bug causing inaccurate query results, while combining ``__raw__`` and regular filters for the same field #2264
 - Add support for the `elemMatch` projection operator in .fields() (e.g BlogPost.objects.fields(elemMatch__comments="test")) #2267
 - DictField validate failed without default connection (bug introduced in 0.19.0) #2239

mongoengine/queryset/base.py

@@ -259,16 +259,18 @@ class BaseQuerySet(object):
         except StopIteration:
             msg = "%s matching query does not exist." % queryset._document._class_name
             raise queryset._document.DoesNotExist(msg)
+
         try:
+            # Check if there is another match
             six.next(queryset)
         except StopIteration:
             return result
 
         # If we were able to retrieve the 2nd doc, rewind the cursor and
         # raise the MultipleObjectsReturned exception.
-        queryset.rewind()
-        message = u"%d items returned, instead of 1" % queryset.count()
-        raise queryset._document.MultipleObjectsReturned(message)
+        raise queryset._document.MultipleObjectsReturned(
+            u"2 or more items returned, instead of 1"
+        )
 
     def create(self, **kwargs):
         """Create new object. Returns the saved object instance.

tests/queryset/test_queryset.py

@@ -274,32 +274,47 @@ class TestQueryset(unittest.TestCase):
         with pytest.raises(InvalidQueryError):
             self.Person.objects(name="User A").with_id(person1.id)
 
-    def test_find_only_one(self):
-        """Ensure that a query using ``get`` returns at most one result.
-        """
+    def test_get_no_document_exists_raises_doesnotexist(self):
+        assert self.Person.objects.count() == 0
         # Try retrieving when no objects exists
         with pytest.raises(DoesNotExist):
             self.Person.objects.get()
         with pytest.raises(self.Person.DoesNotExist):
             self.Person.objects.get()
 
+    def test_get_multiple_match_raises_multipleobjectsreturned(self):
+        """Ensure that a query using ``get`` returns at most one result.
+        """
+        assert self.Person.objects().count() == 0
+
         person1 = self.Person(name="User A", age=20)
         person1.save()
-        person2 = self.Person(name="User B", age=30)
+
+        p = self.Person.objects.get()
+        assert p == person1
+
+        person2 = self.Person(name="User B", age=20)
         person2.save()
 
-        # Retrieve the first person from the database
+        person3 = self.Person(name="User C", age=30)
+        person3.save()
+
+        # .get called without argument
         with pytest.raises(MultipleObjectsReturned):
             self.Person.objects.get()
         with pytest.raises(self.Person.MultipleObjectsReturned):
             self.Person.objects.get()
 
+        # check filtering
+        with pytest.raises(MultipleObjectsReturned):
+            self.Person.objects.get(age__lt=30)
+        with pytest.raises(MultipleObjectsReturned) as exc_info:
+            self.Person.objects(age__lt=30).get()
+        assert "2 or more items returned, instead of 1" == str(exc_info.value)
+
         # Use a query to filter the people found to just person2
         person = self.Person.objects.get(age=30)
-        assert person.name == "User B"
-
-        person = self.Person.objects.get(age__lt=30)
-        assert person.name == "User A"
+        assert person == person3
 
     def test_find_array_position(self):
         """Ensure that query by array position works.