WL#14679: Allow custom class for data type conversion in Django backend

nmariz · nmariz · commit b12b00cb6459 · 2022-01-11T15:46:14.000Z
The Connector/Python Django backend doesn't allow a custom class used
for data type conversion like in the regular connector, which uses
`MySQLConnectionAbstract.set_converter_class()`.

This worklog implements the infrastructure required to enable the usage
of a user-defined custom class to convert non-default data types.
diff --git a/CHANGES.txt b/CHANGES.txt
@@ -12,6 +12,7 @@ v8.0.29
 =======
 
 - WL#14824: Remove Python 3.6 support
+- WL#14679: Allow custom class for data type conversion in Django backend
 
 v8.0.28
 =======
diff --git a/lib/mysql/connector/django/base.py b/lib/mysql/connector/django/base.py
@@ -276,12 +276,22 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
 
-        try:
-            self._use_pure = self.settings_dict['OPTIONS']['use_pure']
-        except KeyError:
-            self._use_pure = not HAVE_CEXT
-
-        self.converter = DjangoMySQLConverter()
+        options = self.settings_dict.get('OPTIONS')
+        if options:
+            self._use_pure = options.get('use_pure', not HAVE_CEXT)
+            converter_class = options.get(
+                'converter_class',
+                DjangoMySQLConverter,
+            )
+            if not issubclass(converter_class, DjangoMySQLConverter):
+                raise ProgrammingError(
+                    'Converter class should be a subclass of '
+                    'mysql.connector.django.base.DjangoMySQLConverter'
+                )
+            self.converter = converter_class()
+        else:
+             self.converter = DjangoMySQLConverter()
+             self._use_pure = not HAVE_CEXT
 
     def __getattr__(self, attr):
         if attr.startswith("mysql_is"):
diff --git a/tests/test_django.py b/tests/test_django.py
@@ -99,10 +99,13 @@
 # Have to load django.db to make importing db backend work for Django < 1.6
 import django.db  # pylint: disable=W0611
 from django.db.backends.signals import connection_created
+from django.db.utils import DEFAULT_DB_ALIAS, load_backend
 from django.utils.safestring import SafeText
 
 import mysql.connector
 from mysql.connector.django.introspection import FieldInfo
+from mysql.connector.conversion import MySQLConverter
+from mysql.connector.errors import ProgrammingError
 
 if DJANGO_AVAILABLE:
     from mysql.connector.django.base import (
@@ -356,6 +359,85 @@ def test__DATETIME_to_python(self):
         settings.USE_TZ = False
 
 
+class CustomDjangoMySQLConverter(DjangoMySQLConverter):
+    """A custom Django MySQL converter."""
+
+    def _CUSTOMTYPE_to_python(self, value):
+        try:
+            return int(value)
+        except ValueError:
+            raise ValueError("Invalid value for CUSTOMTYPE conversion")
+
+
+class CustomDjangoMySQLConverterTests(tests.MySQLConnectorTests):
+    """Test the Django custom MySQL converter class."""
+
+    @staticmethod
+    def create_connection(alias=DEFAULT_DB_ALIAS):
+        django.db.connections.ensure_defaults(alias)
+        django.db.connections.prepare_test_settings(alias)
+        db = django.db.connections.databases[alias]
+        backend = load_backend(db['ENGINE'])
+        return backend.DatabaseWrapper(db, alias)
+
+    def test__TIME_to_python(self):
+        value = b'10:11:12'
+        django_converter = CustomDjangoMySQLConverter()
+        self.assertEqual(
+            datetime.time(10, 11, 12),
+            django_converter._TIME_to_python(value, dsc=None),
+        )
+
+    def test__DATETIME_to_python(self):
+        value = b'1990-11-12 00:00:00'
+        django_converter = CustomDjangoMySQLConverter()
+        self.assertEqual(
+            datetime.datetime(1990, 11, 12, 0, 0, 0),
+            django_converter._DATETIME_to_python(value, dsc=None),
+        )
+
+        settings.USE_TZ = True
+        value = b'0000-00-00 00:00:00'
+        django_converter = DjangoMySQLConverter()
+        self.assertEqual(
+            None,
+            django_converter._DATETIME_to_python(value, dsc=None),
+        )
+        settings.USE_TZ = False
+
+    def test__CUSTOMTYPE_to_python(self):
+        value = b'2021'
+        django_converter = CustomDjangoMySQLConverter()
+        self.assertEqual(
+            2021,
+            django_converter._CUSTOMTYPE_to_python(value),
+        )
+
+    def test_invalid__CUSTOMTYPE_to_python(self):
+        value = b'abc'
+        django_converter = CustomDjangoMySQLConverter()
+        self.assertRaises(
+            ValueError,
+            django_converter._CUSTOMTYPE_to_python,
+            value,
+        )
+
+    def test_invalid_converter_class(self):
+        settings.DATABASES['default']['OPTIONS'] = {
+            'converter_class': MySQLConverter,
+        }
+        self.assertRaises(ProgrammingError, self.create_connection)
+        del settings.DATABASES['default']['OPTIONS']
+
+    def test_converter_class(self):
+        settings.DATABASES['default']['OPTIONS'] = {
+            'converter_class': CustomDjangoMySQLConverter,
+        }
+        cnx = self.create_connection()
+        cnx.close()
+        del settings.DATABASES['default']['OPTIONS']
+
+
 class BugOra20106629(tests.MySQLConnectorTests):
     """CONNECTOR/PYTHON DJANGO BACKEND DOESN'T SUPPORT SAFETEXT"""
 
