Add write concern support for issue #6

- Add WriteConcern import from pymongo
- Add write concern parsing in DatabaseWrapper.__init__()
- Support dict, string, and int write concern formats
- Apply write concern to collections in get_collection()
- Add comprehensive tests for write concern functionality

Author: scarlet2131

django_mongodb_backend/base.py

@@ -10,6 +10,7 @@
 from pymongo.collection import Collection
 from pymongo.driver_info import DriverInfo
 from pymongo.mongo_client import MongoClient
+from pymongo.write_concern import WriteConcern
 
 from . import __version__ as django_mongodb_backend_version
 from . import dbapi as Database
@@ -156,8 +157,29 @@ def _isnull_operator(a, b):
     def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS):
         super().__init__(settings_dict, alias=alias)
         self.session = None
+        self._write_concern = self._parse_write_concern(settings_dict.get('OPTIONS', {}).get('WRITE_CONCERN'))
+
+    def _parse_write_concern(self, write_concern_config):
+        """Parse write concern configuration from Django settings."""
+        if write_concern_config is None:
+            return None
+        
+        if isinstance(write_concern_config, dict):
+            return WriteConcern(**write_concern_config)
+        elif isinstance(write_concern_config, str):
+            return WriteConcern(w=write_concern_config)
+        elif isinstance(write_concern_config, int):
+            return WriteConcern(w=write_concern_config)
+        else:
+            raise ImproperlyConfigured(
+                f"WRITE_CONCERN must be a dict, str, or int, got {type(write_concern_config)}"
+            )
 
     def get_collection(self, name, **kwargs):
+        # Apply write concern if configured
+        if self._write_concern is not None:
+            kwargs.setdefault('write_concern', self._write_concern)
+        
         collection = Collection(self.database, name, **kwargs)
         if self.queries_logged:
             collection = OperationDebugWrapper(self, collection)

tests/backend_/test_write_concern.py

@@ -0,0 +1,73 @@
+from django.core.exceptions import ImproperlyConfigured
+from django.test import TestCase
+from pymongo.write_concern import WriteConcern
+
+from django_mongodb_backend.base import DatabaseWrapper
+
+
+class WriteConcerrTests(TestCase):
+    def test_parse_write_concern_dict(self):
+        """Test parsing write concern from dictionary configuration."""
+        settings_dict = {
+            'NAME': 'test_db',
+            'OPTIONS': {
+                'WRITE_CONCERN': {'w': 'majority', 'j': True, 'wtimeout': 5000}
+            }
+        }
+        wrapper = DatabaseWrapper(settings_dict)
+        
+        self.assertIsInstance(wrapper._write_concern, WriteConcern)
+        self.assertIsNotNone(wrapper._write_concern)
+        self.assertEqual(wrapper._write_concern.document['w'], 'majority')
+        self.assertEqual(wrapper._write_concern.document['j'], True)
+        self.assertEqual(wrapper._write_concern.document['wtimeout'], 5000)
+
+    def test_parse_write_concern_string(self):
+        """Test parsing write concern from string configuration."""
+        settings_dict = {
+            'NAME': 'test_db',
+            'OPTIONS': {
+                'WRITE_CONCERN': 'majority'
+            }
+        }
+        wrapper = DatabaseWrapper(settings_dict)
+        
+        self.assertIsInstance(wrapper._write_concern, WriteConcern)
+        self.assertIsNotNone(wrapper._write_concern)
+        self.assertEqual(wrapper._write_concern.document['w'], 'majority')
+
+    def test_parse_write_concern_int(self):
+        """Test parsing write concern from integer configuration."""
+        settings_dict = {
+            'NAME': 'test_db',
+            'OPTIONS': {
+                'WRITE_CONCERN': 2
+            }
+        }
+        wrapper = DatabaseWrapper(settings_dict)
+        
+        self.assertIsInstance(wrapper._write_concern, WriteConcern)
+        self.assertIsNotNone(wrapper._write_concern)
+        self.assertEqual(wrapper._write_concern.document['w'], 2)
+
+    def test_parse_write_concern_none(self):
+        """Test that None write concern config results in None."""
+        settings_dict = {
+            'NAME': 'test_db',
+            'OPTIONS': {}
+        }
+        wrapper = DatabaseWrapper(settings_dict)
+        
+        self.assertIsNone(wrapper._write_concern)
+
+    def test_parse_write_concern_invalid_type(self):
+        """Test that invalid write concern type raises ImproperlyConfigured."""
+        settings_dict = {
+            'NAME': 'test_db',
+            'OPTIONS': {
+                'WRITE_CONCERN': ['invalid', 'type']
+            }
+        }
+        
+        with self.assertRaises(ImproperlyConfigured):
+            DatabaseWrapper(settings_dict)