INTPYTHON-743 Allow using MongoDB connection string in DATABASES["HOST"]

Author: timgraham

.github/workflows/mongodb_settings.py

@@ -1,13 +1,16 @@
 import os
 
-from django_mongodb_backend import parse_uri
+from pymongo.uri_parser import parse_uri
 
 if mongodb_uri := os.getenv("MONGODB_URI"):
-    db_settings = parse_uri(mongodb_uri, db_name="dummy")
-
+    db_settings = {
+        "ENGINE": "django_mongodb_backend",
+        "HOST": mongodb_uri,
+    }
     # Workaround for https://github.com/mongodb-labs/mongo-orchestration/issues/268
-    if db_settings["USER"] and db_settings["PASSWORD"]:
-        db_settings["OPTIONS"].update({"tls": True, "tlsAllowInvalidCertificates": True})
+    uri = parse_uri(mongodb_uri)
+    if uri.get("username") and uri.get("password"):
+        db_settings["OPTIONS"] = {"tls": True, "tlsAllowInvalidCertificates": True}
     DATABASES = {
         "default": {**db_settings, "NAME": "djangotests"},
         "other": {**db_settings, "NAME": "djangotests-other"},

README.md

@@ -45,9 +45,11 @@ setting like so:
 
 ```python
 DATABASES = {
-    "default": django_mongodb_backend.parse_uri(
-        "<CONNECTION_STRING_URI>", db_name="example"
-    ),
+    "default": {
+        "ENGINE": "django_mongodb_backend",
+        "HOST": "<CONNECTION_STRING_URI>",
+        "NAME": "db_name",
+    },
 }
 ```
 

django_mongodb_backend/base.py

@@ -11,6 +11,7 @@
 from pymongo.collection import Collection
 from pymongo.driver_info import DriverInfo
 from pymongo.mongo_client import MongoClient
+from pymongo.uri_parser import parse_uri
 
 from . import __version__ as django_mongodb_backend_version
 from . import dbapi as Database
@@ -157,6 +158,18 @@ def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS):
         self.in_atomic_block_mongo = False
         # Current number of nested 'atomic' calls.
         self.nested_atomics = 0
+        # If database "NAME" isn't specified, try to get it from HOST, if it's
+        # a connection string.
+        if self.settings_dict["NAME"] == "":  # Empty string = unspecified; None = _nodb_cursor()
+            name_is_missing = True
+            host = self.settings_dict["HOST"]
+            if host.startswith(("mongodb://", "mongodb+srv://")):
+                uri = parse_uri(host)
+                if database := uri.get("database"):
+                    self.settings_dict["NAME"] = database
+                    name_is_missing = False
+            if name_is_missing:
+                raise ImproperlyConfigured('settings.DATABASES is missing the "NAME" value.')
 
     def get_collection(self, name, **kwargs):
         collection = Collection(self.database, name, **kwargs)
@@ -183,15 +196,19 @@ def init_connection_state(self):
 
     def get_connection_params(self):
         settings_dict = self.settings_dict
-        if not settings_dict["NAME"]:
-            raise ImproperlyConfigured('settings.DATABASES is missing the "NAME" value.')
-        return {
+        params = {
             "host": settings_dict["HOST"] or None,
-            "port": int(settings_dict["PORT"] or 27017),
-            "username": settings_dict.get("USER"),
-            "password": settings_dict.get("PASSWORD"),
             **settings_dict["OPTIONS"],
         }
+        # MongoClient uses any of these parameters (including "OPTIONS" above)
+        # to override any corresponding values in a connection string "HOST".
+        if user := settings_dict.get("USER"):
+            params["username"] = user
+        if password := settings_dict.get("PASSWORD"):
+            params["password"] = password
+        if port := settings_dict.get("PORT"):
+            params["port"] = int(port)
+        return params
 
     @async_unsafe
     def get_new_connection(self, conn_params):

docs/intro/configure.rst

@@ -105,8 +105,26 @@ to match the first two numbers from your version.)
 Configuring the ``DATABASES`` setting
 =====================================
 
-After you've set up a project, configure Django's :setting:`DATABASES` setting
-similar to this::
+After you've set up a project, configure Django's :setting:`DATABASES` setting.
+
+If you have a connection string, you can provide it like this::
+
+    DATABASES = {
+        "default": {
+            "ENGINE": "django_mongodb_backend",
+            "HOST": "mongodb+srv://my_user:[email protected]/?retryWrites=true&w=majority&tls=false",
+            "NAME": "my_database",
+        },
+    }
+
+.. versionchanged:: 5.2.1
+
+    Support for the connection string in ``"HOST"`` was added. Previous
+    versions recommended using :func:`~django_mongodb_backend.utils.parse_uri`.
+
+Alternatively, you can separate the connection string so that your settings
+look more like what you usually see with Django. This constructs a
+:setting:`DATABASES` setting equivalent to the first example::
 
     DATABASES = {
         "default": {
@@ -117,7 +135,6 @@ similar to this::
             "PASSWORD": "my_password",
             "PORT": 27017,
             "OPTIONS": {
-                # Example:
                 "retryWrites": "true",
                 "w": "majority",
                 "tls": "false",
@@ -128,8 +145,8 @@ similar to this::
 For a localhost configuration, you can omit :setting:`HOST` or specify
 ``"HOST": "localhost"``.
 
-:setting:`HOST` only needs a scheme prefix for SRV connections
-(``mongodb+srv://``). A ``mongodb://`` prefix is never required.
+If you provide a connection string in ``HOST``, any of the other values below
+will override the values in the connection string.
 
 :setting:`OPTIONS` is an optional dictionary of parameters that will be passed
 to :class:`~pymongo.mongo_client.MongoClient`.
@@ -143,17 +160,6 @@ For a replica set or sharded cluster where you have multiple hosts, include
 all of them in :setting:`HOST`, e.g.
 ``"mongodb://mongos0.example.com:27017,mongos1.example.com:27017"``.
 
-Alternatively, if you prefer to simply paste in a MongoDB URI rather than parse
-it into the format above, you can use
-:func:`~django_mongodb_backend.utils.parse_uri`::
-
-    import django_mongodb_backend
-
-    MONGODB_URI = "mongodb+srv://my_user:[email protected]/myDatabase?retryWrites=true&w=majority&tls=false"
-    DATABASES["default"] = django_mongodb_backend.parse_uri(MONGODB_URI)
-
-This constructs a :setting:`DATABASES` setting equivalent to the first example.
-
 .. _configuring-database-routers-setting:
 
 Configuring the ``DATABASE_ROUTERS`` setting

docs/releases/5.2.x.rst

@@ -10,7 +10,10 @@ Django MongoDB Backend 5.2.x
 New features
 ------------
 
-- ...
+- Allowed :ref:`specifying the MongoDB connection string
+  <configuring-databases-setting>` in ``DATABASES["HOST"]``, eliminating the
+  need to use :func:`~django_mongodb_backend.utils.parse_uri` to configure the
+  :setting:`DATABASES` setting.
 
 Bug fixes
 ---------

tests/backend_/test_base.py

@@ -1,3 +1,5 @@
+from unittest.mock import patch
+
 from django.core.exceptions import ImproperlyConfigured
 from django.db import connection
 from django.db.backends.signals import connection_created
@@ -6,14 +8,45 @@
 from django_mongodb_backend.base import DatabaseWrapper
 
 
-class GetConnectionParamsTests(SimpleTestCase):
+class DatabaseWrapperTests(SimpleTestCase):
     def test_database_name_empty(self):
         settings = connection.settings_dict.copy()
         settings["NAME"] = ""
         msg = 'settings.DATABASES is missing the "NAME" value.'
         with self.assertRaisesMessage(ImproperlyConfigured, msg):
-            DatabaseWrapper(settings).get_connection_params()
+            DatabaseWrapper(settings)
+
+    def test_database_name_empty_and_host_does_not_contain_database(self):
+        settings = connection.settings_dict.copy()
+        settings["NAME"] = ""
+        settings["HOST"] = "mongodb://localhost"
+        msg = 'settings.DATABASES is missing the "NAME" value.'
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            DatabaseWrapper(settings)
+
+    def test_database_name_parsed_from_host(self):
+        settings = connection.settings_dict.copy()
+        settings["NAME"] = ""
+        settings["HOST"] = "mongodb://localhost/db"
+        self.assertEqual(DatabaseWrapper(settings).settings_dict["NAME"], "db")
 
+    def test_database_name_parsed_from_srv_host(self):
+        settings = connection.settings_dict.copy()
+        settings["NAME"] = ""
+        settings["HOST"] = "mongodb+srv://localhost/db"
+        # patch() prevents a crash when PyMongo attempts to resolve the
+        # nonexistent SRV record.
+        with patch("dns.resolver.resolve"):
+            self.assertEqual(DatabaseWrapper(settings).settings_dict["NAME"], "db")
+
+    def test_database_name_not_overridden_by_host(self):
+        settings = connection.settings_dict.copy()
+        settings["NAME"] = "not overridden"
+        settings["HOST"] = "mongodb://localhost/db"
+        self.assertEqual(DatabaseWrapper(settings).settings_dict["NAME"], "not overridden")
+
+
+class GetConnectionParamsTests(SimpleTestCase):
     def test_host(self):
         settings = connection.settings_dict.copy()
         settings["HOST"] = "host"
@@ -56,6 +89,22 @@ def test_options(self):
         params = DatabaseWrapper(settings).get_connection_params()
         self.assertEqual(params["extra"], "option")
 
+    def test_unspecified_settings_omitted(self):
+        settings = connection.settings_dict.copy()
+        # django.db.utils.ConnectionHandler sets unspecified values to an empty
+        # string.
+        settings.update(
+            {
+                "USER": "",
+                "PASSWORD": "",
+                "PORT": "",
+            }
+        )
+        params = DatabaseWrapper(settings).get_connection_params()
+        self.assertNotIn("username", params)
+        self.assertNotIn("password", params)
+        self.assertNotIn("port", params)
+
 
 class DatabaseWrapperConnectionTests(TestCase):
     def test_set_autocommit(self):