Create initial 2.0 engine implementation

Implemented the SQLAlchemy 2 :func:`.future.create_engine` function which
is used for forwards compatibility with SQLAlchemy 2.   This engine
features always-transactional behavior with autobegin.

Allow execution options per statement execution.  This includes
that the before_execute() and after_execute() events now accept
an additional dictionary with these options, empty if not
passed; a legacy event decorator is added for backwards compatibility
which now also emits a deprecation warning.

Add some basic tests for execution, transactions, and
the new result object.   Build out on a new testing fixture
that swaps in the future engine completely to start with.

Change-Id: I70e7338bb3f0ce22d2f702537d94bb249bd9fb0a
Fixes: #4644

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index 49bb08644..d8b5a1626 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -282,9 +282,13 @@ class ClauseElement(
         d.pop("_generate_cache_key", None)
         return d
 
-    def _execute_on_connection(self, connection, multiparams, params):
+    def _execute_on_connection(
+        self, connection, multiparams, params, execution_options
+    ):
         if self.supports_execution:
-            return connection._execute_clauseelement(self, multiparams, params)
+            return connection._execute_clauseelement(
+                self, multiparams, params, execution_options
+            )
         else:
             raise exc.ObjectNotExecutableError(self)