Merge pull request #2031 from yandrieiev/fail_fast_when_invalid_db_name

Fail fast when db name is invalid

AUTHORS

@@ -251,3 +251,4 @@ that much better:
  * Gleb Voropaev (https://github.com/buggyspace)
  * Paulo Amaral (https://github.com/pauloAmaral)
  * Gaurav Dadhania (https://github.com/GVRV)
+ * Yurii Andrieiev (https://github.com/yandrieiev)

docs/changelog.rst

@@ -7,6 +7,7 @@ Development
 - POTENTIAL BREAKING CHANGE: Aggregate gives wrong results when used with a queryset having limit and skip #2029
 - mongoengine now requires pymongo>=3.5 #2017
 - Generate Unique Indices for SortedListField and EmbeddedDocumentListFields #2020
+- connect() fails immediately when db name contains invalid characters (e. g. when user mistakenly puts 'mongodb://127.0.0.1:27017' as db name, happened in #1718) or is if db name is of an invalid type
 - (Fill this out as you fix issues and develop your features).
 
 Changes in 0.17.0

mongoengine/connection.py

@@ -1,4 +1,5 @@
 from pymongo import MongoClient, ReadPreference, uri_parser
+from pymongo.database import _check_name
 import six
 
 from mongoengine.pymongo_support import IS_PYMONGO_3
@@ -28,6 +29,16 @@ _connections = {}
 _dbs = {}
 
 
+def check_db_name(name):
+    """Check if a database name is valid.
+    This functionality is copied from pymongo Database class constructor.
+    """
+    if not isinstance(name, six.string_types):
+        raise TypeError('name must be an instance of %s' % six.string_types)
+    elif name != '$external':
+        _check_name(name)
+
+
 def register_connection(alias, db=None, name=None, host=None, port=None,
                         read_preference=READ_PREFERENCE,
                         username=None, password=None,
@@ -69,6 +80,7 @@ def register_connection(alias, db=None, name=None, host=None, port=None,
         'authentication_mechanism': authentication_mechanism
     }
 
+    check_db_name(conn_settings['name'])
     conn_host = conn_settings['host']
 
     # Host can be a list or a string, so if string, force to a list.

tests/test_connection.py

@@ -1,5 +1,5 @@
 import datetime
-from pymongo.errors import OperationFailure
+from pymongo.errors import OperationFailure, InvalidName
 
 try:
     import unittest2 as unittest
@@ -49,6 +49,36 @@ class ConnectionTest(unittest.TestCase):
         conn = get_connection('testdb')
         self.assertIsInstance(conn, pymongo.mongo_client.MongoClient)
 
+    def test_connect_with_invalid_db_name(self):
+        """Ensure that connect() method fails fast if db name is invalid
+        """
+        with self.assertRaises(InvalidName):
+            connect('mongomock://localhost')
+
+    def test_connect_with_db_name_external(self):
+        """Ensure that connect() works if db name is $external
+        """
+        """Ensure that the connect() method works properly."""
+        connect('$external')
+
+        conn = get_connection()
+        self.assertIsInstance(conn, pymongo.mongo_client.MongoClient)
+
+        db = get_db()
+        self.assertIsInstance(db, pymongo.database.Database)
+        self.assertEqual(db.name, '$external')
+
+        connect('$external', alias='testdb')
+        conn = get_connection('testdb')
+        self.assertIsInstance(conn, pymongo.mongo_client.MongoClient)
+
+    def test_connect_with_invalid_db_name_type(self):
+        """Ensure that connect() method fails fast if db name has invalid type
+        """
+        with self.assertRaises(TypeError):
+            non_string_db_name = ['e. g. list instead of a string']
+            connect(non_string_db_name)
+
     def test_connect_in_mocking(self):
         """Ensure that the connect() method works properly in mocking.
         """