Surface driver connection object when using a proxied dialect

Improve the interface used by adapted drivers, like the asyncio ones,
to access the actual connection object returned by the driver.

The :class:`_engine._ConnectionRecord` and
:class:`_engine._ConnectionFairy` now have two new attributes:

* ``dbapi_connection`` always represents a DBAPI compatible
object.  For pep-249 drivers, this is the DBAPI connection as it always
has been, previously accessed under the ``.connection`` attribute.
For asyncio drivers that SQLAlchemy adapts into a pep-249 interface,
the returned object will normally be a SQLAlchemy adaption object
called :class:`_engine.AdaptedConnection`.
* ``driver_connection`` always represents the actual connection object
maintained by the third party pep-249 DBAPI or async driver in use.
For standard pep-249 DBAPIs, this will always be the same object
as that of the ``dbapi_connection``.  For an asyncio driver, it will be
the underlying asyncio-only connection object.

The ``.connection`` attribute remains available and is now a legacy alias
of ``.dbapi_connection``.

Fixes: #6832
Change-Id: Ib72f97deefca96dce4e61e7c38ba430068d6a82e

2 files changed, 9 insertions, 5 deletions

diff --git a/lib/sqlalchemy/dialects/sqlite/aiosqlite.py b/lib/sqlalchemy/dialects/sqlite/aiosqlite.py
index eb750b0e7..4319e2661 100644
--- a/lib/sqlalchemy/dialects/sqlite/aiosqlite.py
+++ b/lib/sqlalchemy/dialects/sqlite/aiosqlite.py
@@ -41,6 +41,7 @@ from .base import SQLiteExecutionContext
 from .pysqlite import SQLiteDialect_pysqlite
 from ... import pool
 from ... import util
+from ...engine import AdaptedConnection
 from ...util.concurrency import await_fallback
 from ...util.concurrency import await_only
 
@@ -162,7 +163,7 @@ class AsyncAdapt_aiosqlite_ss_cursor(AsyncAdapt_aiosqlite_cursor):
         return self.await_(self._cursor.fetchall())
 
 
-class AsyncAdapt_aiosqlite_connection:
+class AsyncAdapt_aiosqlite_connection(AdaptedConnection):
     await_ = staticmethod(await_only)
     __slots__ = ("dbapi", "_connection")
 
@@ -328,5 +329,8 @@ class SQLiteDialect_aiosqlite(SQLiteDialect_pysqlite):
 
         return super().is_disconnect(e, connection, cursor)
 
+    def get_driver_connection(self, connection):
+        return connection._connection
+
 
 dialect = SQLiteDialect_aiosqlite
diff --git a/lib/sqlalchemy/dialects/sqlite/pysqlite.py b/lib/sqlalchemy/dialects/sqlite/pysqlite.py
index 0f96e8830..e9d5d9682 100644
--- a/lib/sqlalchemy/dialects/sqlite/pysqlite.py
+++ b/lib/sqlalchemy/dialects/sqlite/pysqlite.py
@@ -499,8 +499,8 @@ class SQLiteDialect_pysqlite(SQLiteDialect):
     )
 
     def set_isolation_level(self, connection, level):
-        if hasattr(connection, "connection"):
-            dbapi_connection = connection.connection
+        if hasattr(connection, "dbapi_connection"):
+            dbapi_connection = connection.dbapi_connection
         else:
             dbapi_connection = connection
 
@@ -521,8 +521,8 @@ class SQLiteDialect_pysqlite(SQLiteDialect):
             return re.search(a, b) is not None
 
         def set_regexp(connection):
-            if hasattr(connection, "connection"):
-                dbapi_connection = connection.connection
+            if hasattr(connection, "dbapi_connection"):
+                dbapi_connection = connection.dbapi_connection
             else:
                 dbapi_connection = connection
             dbapi_connection.create_function(