Fixed #27170 -- Added DatabaseWrapper class attributes to ease subclassing.

11 files changed, 87 insertions, 70 deletions

diff --git a/django/contrib/gis/db/backends/mysql/base.py b/django/contrib/gis/db/backends/mysql/base.py
index d252b38804..9cf61e40d2 100644
--- a/django/contrib/gis/db/backends/mysql/base.py
+++ b/django/contrib/gis/db/backends/mysql/base.py
@@ -9,9 +9,7 @@ from .schema import MySQLGISSchemaEditor
 
 class DatabaseWrapper(MySQLDatabaseWrapper):
     SchemaEditorClass = MySQLGISSchemaEditor
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-        self.features = DatabaseFeatures(self)
-        self.ops = MySQLOperations(self)
-        self.introspection = MySQLIntrospection(self)
+    # Classes instantiated in __init__().
+    features_class = DatabaseFeatures
+    introspection_class = MySQLIntrospection
+    ops_class = MySQLOperations
diff --git a/django/contrib/gis/db/backends/oracle/base.py b/django/contrib/gis/db/backends/oracle/base.py
index 167b61d01b..a4f6684f6d 100644
--- a/django/contrib/gis/db/backends/oracle/base.py
+++ b/django/contrib/gis/db/backends/oracle/base.py
@@ -9,9 +9,7 @@ from .schema import OracleGISSchemaEditor
 
 class DatabaseWrapper(OracleDatabaseWrapper):
     SchemaEditorClass = OracleGISSchemaEditor
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-        self.features = DatabaseFeatures(self)
-        self.ops = OracleOperations(self)
-        self.introspection = OracleIntrospection(self)
+    # Classes instantiated in __init__().
+    features_class = DatabaseFeatures
+    introspection_class = OracleIntrospection
+    ops_class = OracleOperations
diff --git a/django/contrib/gis/db/backends/spatialite/base.py b/django/contrib/gis/db/backends/spatialite/base.py
index 44514a87d4..1f03868945 100644
--- a/django/contrib/gis/db/backends/spatialite/base.py
+++ b/django/contrib/gis/db/backends/spatialite/base.py
@@ -17,6 +17,11 @@ from .schema import SpatialiteSchemaEditor
 
 class DatabaseWrapper(SQLiteDatabaseWrapper):
     SchemaEditorClass = SpatialiteSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = SpatiaLiteClient
+    features_class = DatabaseFeatures
+    introspection_class = SpatiaLiteIntrospection
+    ops_class = SpatiaLiteOperations
 
     def __init__(self, *args, **kwargs):
         # Before we get too far, make sure pysqlite 2.5+ is installed.
@@ -37,10 +42,6 @@ class DatabaseWrapper(SQLiteDatabaseWrapper):
                                        'SPATIALITE_LIBRARY_PATH in your settings.'
                                        )
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
-        self.features = DatabaseFeatures(self)
-        self.ops = SpatiaLiteOperations(self)
-        self.client = SpatiaLiteClient(self)
-        self.introspection = SpatiaLiteIntrospection(self)
 
     def get_new_connection(self, conn_params):
         conn = super(DatabaseWrapper, self).get_new_connection(conn_params)
diff --git a/django/db/backends/base/base.py b/django/db/backends/base/base.py
index fcafa5f71a..595d191dce 100644
--- a/django/db/backends/base/base.py
+++ b/django/db/backends/base/base.py
@@ -8,6 +8,7 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.db import DEFAULT_DB_ALIAS
 from django.db.backends import utils
+from django.db.backends.base.validation import BaseDatabaseValidation
 from django.db.backends.signals import connection_created
 from django.db.transaction import TransactionManagementError
 from django.db.utils import DatabaseError, DatabaseErrorWrapper
@@ -36,6 +37,13 @@ class BaseDatabaseWrapper(object):
     ops = None
     vendor = 'unknown'
     SchemaEditorClass = None
+    # Classes instantiated in __init__().
+    client_class = None
+    creation_class = None
+    features_class = None
+    introspection_class = None
+    ops_class = None
+    validation_class = BaseDatabaseValidation
 
     queries_limit = 9000
 
@@ -88,6 +96,13 @@ class BaseDatabaseWrapper(object):
         # is called?
         self.run_commit_hooks_on_set_autocommit_on = False
 
+        self.client = self.client_class(self)
+        self.creation = self.creation_class(self)
+        self.features = self.features_class(self)
+        self.introspection = self.introspection_class(self)
+        self.ops = self.ops_class(self)
+        self.validation = self.validation_class(self)
+
     def ensure_timezone(self):
         """
         Ensure the connection's timezone is set to `self.timezone_name` and
diff --git a/django/db/backends/dummy/base.py b/django/db/backends/dummy/base.py
index f45d913bef..602bfb8fe6 100644
--- a/django/db/backends/dummy/base.py
+++ b/django/db/backends/dummy/base.py
@@ -13,7 +13,6 @@ from django.db.backends.base.client import BaseDatabaseClient
 from django.db.backends.base.creation import BaseDatabaseCreation
 from django.db.backends.base.introspection import BaseDatabaseIntrospection
 from django.db.backends.base.operations import BaseDatabaseOperations
-from django.db.backends.base.validation import BaseDatabaseValidation
 from django.db.backends.dummy.features import DummyDatabaseFeatures
 
 
@@ -71,16 +70,12 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     _savepoint_commit = complain
     _savepoint_rollback = ignore
     _set_autocommit = complain
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-
-        self.features = DummyDatabaseFeatures(self)
-        self.ops = DatabaseOperations(self)
-        self.client = DatabaseClient(self)
-        self.creation = DatabaseCreation(self)
-        self.introspection = DatabaseIntrospection(self)
-        self.validation = BaseDatabaseValidation(self)
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DummyDatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
 
     def is_usable(self):
         return True
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index 94415139cc..472b2b98df 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -227,16 +227,13 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
     Database = Database
     SchemaEditorClass = DatabaseSchemaEditor
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-
-        self.features = DatabaseFeatures(self)
-        self.ops = DatabaseOperations(self)
-        self.client = DatabaseClient(self)
-        self.creation = DatabaseCreation(self)
-        self.introspection = DatabaseIntrospection(self)
-        self.validation = DatabaseValidation(self)
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
+    validation_class = DatabaseValidation
 
     def get_connection_params(self):
         kwargs = {
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 91af08acb6..c4dc075355 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -15,7 +15,6 @@ import warnings
 from django.conf import settings
 from django.db import utils
 from django.db.backends.base.base import BaseDatabaseWrapper
-from django.db.backends.base.validation import BaseDatabaseValidation
 from django.utils import six, timezone
 from django.utils.deprecation import RemovedInDjango20Warning
 from django.utils.duration import duration_string
@@ -179,18 +178,17 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
     Database = Database
     SchemaEditorClass = DatabaseSchemaEditor
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
 
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
-
-        self.features = DatabaseFeatures(self)
         use_returning_into = self.settings_dict["OPTIONS"].get('use_returning_into', True)
         self.features.can_return_id_from_insert = use_returning_into
-        self.ops = DatabaseOperations(self)
-        self.client = DatabaseClient(self)
-        self.creation = DatabaseCreation(self)
-        self.introspection = DatabaseIntrospection(self)
-        self.validation = BaseDatabaseValidation(self)
 
     def _connect_string(self):
         settings_dict = self.settings_dict
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 19afa48047..1ab05d81f6 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -10,7 +10,6 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.db import DEFAULT_DB_ALIAS
 from django.db.backends.base.base import BaseDatabaseWrapper
-from django.db.backends.base.validation import BaseDatabaseValidation
 from django.db.utils import DatabaseError as WrappedDatabaseError
 from django.utils import six
 from django.utils.encoding import force_str
@@ -141,16 +140,12 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
     Database = Database
     SchemaEditorClass = DatabaseSchemaEditor
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-
-        self.features = DatabaseFeatures(self)
-        self.ops = DatabaseOperations(self)
-        self.client = DatabaseClient(self)
-        self.creation = DatabaseCreation(self)
-        self.introspection = DatabaseIntrospection(self)
-        self.validation = BaseDatabaseValidation(self)
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
 
     def get_connection_params(self):
         settings_dict = self.settings_dict
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index 0d6b4e3d00..e8b707861f 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -15,7 +15,6 @@ from django.conf import settings
 from django.db import utils
 from django.db.backends import utils as backend_utils
 from django.db.backends.base.base import BaseDatabaseWrapper
-from django.db.backends.base.validation import BaseDatabaseValidation
 from django.utils import six, timezone
 from django.utils.dateparse import (
     parse_date, parse_datetime, parse_duration, parse_time,
@@ -163,16 +162,12 @@ class DatabaseWrapper(BaseDatabaseWrapper):
 
     Database = Database
     SchemaEditorClass = DatabaseSchemaEditor
-
-    def __init__(self, *args, **kwargs):
-        super(DatabaseWrapper, self).__init__(*args, **kwargs)
-
-        self.features = DatabaseFeatures(self)
-        self.ops = DatabaseOperations(self)
-        self.client = DatabaseClient(self)
-        self.creation = DatabaseCreation(self)
-        self.introspection = DatabaseIntrospection(self)
-        self.validation = BaseDatabaseValidation(self)
+    # Classes instantiated in __init__().
+    client_class = DatabaseClient
+    creation_class = DatabaseCreation
+    features_class = DatabaseFeatures
+    introspection_class = DatabaseIntrospection
+    ops_class = DatabaseOperations
 
     def get_connection_params(self):
         settings_dict = self.settings_dict
diff --git a/tests/backends/tests.py b/tests/backends/tests.py
index 4851995149..106fd7f856 100644
--- a/tests/backends/tests.py
+++ b/tests/backends/tests.py
@@ -32,6 +32,31 @@ from django.utils.six.moves import range
 from . import models
 
 
+class DatabaseWrapperTests(SimpleTestCase):
+
+    def test_initialization_class_attributes(self):
+        """
+        The "initialization" class attributes like client_class and
+        creation_class should be set on the class and reflected in the
+        corresponding instance attributes of the instantiated backend.
+        """
+        conn = connections[DEFAULT_DB_ALIAS]
+        conn_class = type(conn)
+        attr_names = [
+            ('client_class', 'client'),
+            ('creation_class', 'creation'),
+            ('features_class', 'features'),
+            ('introspection_class', 'introspection'),
+            ('ops_class', 'ops'),
+            ('validation_class', 'validation'),
+        ]
+        for class_attr_name, instance_attr_name in attr_names:
+            class_attr_value = getattr(conn_class, class_attr_name)
+            self.assertIsNotNone(class_attr_value)
+            instance_attr_value = getattr(conn, instance_attr_name)
+            self.assertIsInstance(instance_attr_value, class_attr_value)
+
+
 class DummyBackendTest(SimpleTestCase):
 
     def test_no_databases(self):
diff --git a/tests/test_runner/tests.py b/tests/test_runner/tests.py
index c2ad07013c..15417db645 100644
--- a/tests/test_runner/tests.py
+++ b/tests/test_runner/tests.py
@@ -281,7 +281,7 @@ class SetupDatabasesTests(unittest.TestCase):
             }
         })
 
-        with mock.patch('django.db.backends.dummy.base.DatabaseCreation') as mocked_db_creation:
+        with mock.patch('django.db.backends.dummy.base.DatabaseWrapper.creation_class') as mocked_db_creation:
             with mock.patch('django.test.utils.connections', new=tested_connections):
                 old_config = self.runner_instance.setup_databases()
                 self.runner_instance.teardown_databases(old_config)
@@ -306,7 +306,7 @@ class SetupDatabasesTests(unittest.TestCase):
                 'ENGINE': 'django.db.backends.dummy',
             },
         })
-        with mock.patch('django.db.backends.dummy.base.DatabaseCreation') as mocked_db_creation:
+        with mock.patch('django.db.backends.dummy.base.DatabaseWrapper.creation_class') as mocked_db_creation:
             with mock.patch('django.test.utils.connections', new=tested_connections):
                 self.runner_instance.setup_databases()
         mocked_db_creation.return_value.create_test_db.assert_called_once_with(
@@ -320,7 +320,7 @@ class SetupDatabasesTests(unittest.TestCase):
                 'TEST': {'SERIALIZE': False},
             },
         })
-        with mock.patch('django.db.backends.dummy.base.DatabaseCreation') as mocked_db_creation:
+        with mock.patch('django.db.backends.dummy.base.DatabaseWrapper.creation_class') as mocked_db_creation:
             with mock.patch('django.test.utils.connections', new=tested_connections):
                 self.runner_instance.setup_databases()
         mocked_db_creation.return_value.create_test_db.assert_called_once_with(