From 928770c43a892e7e6a01e5a85f5d90a5b9a63c72 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastien=20G=C3=A9rard?= <bastien.gerard@cluepoints.com>
Date: Fri, 20 Dec 2019 21:50:00 +0100
Subject: [PATCH] switching  to count_documents

---
 mongoengine/pymongo_support.py   | 28 ++++++++++++++++++++++++----
 mongoengine/queryset/base.py     | 32 +++++++++++++++++++++++++++++++-
 mongoengine/queryset/queryset.py |  1 +
 tests/test_connection.py         |  2 +-
 4 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/mongoengine/pymongo_support.py b/mongoengine/pymongo_support.py
index 80c0661b..1fea9525 100644
--- a/mongoengine/pymongo_support.py
+++ b/mongoengine/pymongo_support.py
@@ -10,12 +10,32 @@ PYMONGO_VERSION = tuple(pymongo.version_tuple[:2])
 IS_PYMONGO_GTE_37 = PYMONGO_VERSION >= _PYMONGO_37
 
 
-def count_documents(collection, filter):
-    """Pymongo>3.7 deprecates count in favour of count_documents"""
+def count_documents(collection, filter, skip=None, limit=None, hint=None, collation=None):
+    """Pymongo>3.7 deprecates count in favour of count_documents
+    """
+    if limit == 0:
+        return 0  # Pymongo raises an OperationFailure if called with limit=0
+
     if IS_PYMONGO_GTE_37:
-        return collection.count_documents(filter)
+        kwargs = {}
+        if skip is not None:
+            kwargs["skip"] = skip
+        if limit is not None:
+            kwargs["limit"] = limit
+        if collation is not None:
+            kwargs["collation"] = collation
+        if hint not in (-1, None):
+            kwargs["hint"] = hint
+        return collection.count_documents(filter=filter, **kwargs)
     else:
-        count = collection.find(filter).count()
+        cursor = collection.find(filter)
+        if limit:
+            cursor = cursor.limit(limit)
+        if skip:
+            cursor = cursor.skip(skip)
+        if hint != -1:
+            cursor = cursor.hint(hint)
+        count = cursor.count()
     return count
 
 
diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 50cb37ac..d7b4007e 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -12,6 +12,7 @@ import pymongo.errors
 from pymongo.collection import ReturnDocument
 from pymongo.common import validate_read_preference
 import six
+from pymongo.errors import OperationFailure
 from six import iteritems
 
 from mongoengine import signals
@@ -26,6 +27,7 @@ from mongoengine.errors import (
     NotUniqueError,
     OperationError,
 )
+from mongoengine.pymongo_support import count_documents
 from mongoengine.queryset import transform
 from mongoengine.queryset.field_list import QueryFieldList
 from mongoengine.queryset.visitor import Q, QNode
@@ -392,9 +394,37 @@ class BaseQuerySet(object):
             :meth:`skip` that has been applied to this cursor into account when
             getting the count
         """
+        # mimic the fact that setting .limit(0) in pymongo sets no limit
+        # https://docs.mongodb.com/manual/reference/method/cursor.limit/#zero-value
         if self._limit == 0 and with_limit_and_skip is False or self._none:
             return 0
-        count = self._cursor.count(with_limit_and_skip=with_limit_and_skip)
+
+        kwargs = (
+            {"limit": self._limit, "skip": self._skip} if with_limit_and_skip else {}
+        )
+
+        if self._limit == 0:
+            # mimic the fact that historically .limit(0) sets no limit
+            kwargs.pop('limit', None)
+
+        if self._hint not in (-1, None):
+            kwargs["hint"] = self._hint
+
+        if self._collation:
+            kwargs["collation"] = self._collation
+
+        try:
+            count = count_documents(
+                collection=self._cursor.collection,
+                filter=self._cursor._Cursor__spec,
+                **kwargs
+            )
+        except OperationFailure:
+            # Accounts for some operators that used to work with .count but are no longer working
+            # with count_documents (i.e $geoNear, $near, and $nearSphere)
+            # fallback to deprecated Cursor.count
+            count = self._cursor.count(with_limit_and_skip=with_limit_and_skip)
+
         self._cursor_obj = None
         return count
 
diff --git a/mongoengine/queryset/queryset.py b/mongoengine/queryset/queryset.py
index 4ba62d46..cc1891f6 100644
--- a/mongoengine/queryset/queryset.py
+++ b/mongoengine/queryset/queryset.py
@@ -146,6 +146,7 @@ class QuerySet(BaseQuerySet):
             return super(QuerySet, self).count(with_limit_and_skip)
 
         if self._len is None:
+            # cache the length
             self._len = super(QuerySet, self).count(with_limit_and_skip)
 
         return self._len
diff --git a/tests/test_connection.py b/tests/test_connection.py
index e40a6994..542da4f0 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -282,7 +282,7 @@ class ConnectionTest(unittest.TestCase):
         # database won't exist until we save a document
         some_document.save()
         assert conn.get_default_database().name == "mongoenginetest"
-        assert conn.database_names()[0] == "mongoenginetest"
+        assert conn.list_database_names()[0] == "mongoenginetest"
 
     @require_mongomock
     def test_connect_with_host_list(self):