Update transaction / connection handling

step one, do away with __connection attribute and using
awkward AttributeError logic

step two, move all management of "connection._transaction"
into the transaction objects themselves where it's easier
to follow.

build MarkerTransaction that takes the role of
"do-nothing block"

new connection datamodel is: connection._transaction, always
a root, connection._nested_transaction, always a nested.

nested transactions still chain to each other as this
is still sort of necessary but they consider the root
transaction separately, and the marker transactions
not at all.

introduce new InvalidRequestError subclass
PendingRollbackError.  Apply to connection and session
for all cases where a transaction needs to be rolled
back before continuing.   Within Connection,
both PendingRollbackError as well as ResourceClosedError
are now raised directly without being handled by
handle_dbapi_error();  this removes these two exception
cases from the handle_error event handler as well as
from StatementError wrapping, as these two exceptions are
not statement oriented and are instead programmatic
issues, that the application is failing to handle database
errors properly.

Revise savepoints so that when a release fails, they set
themselves as inactive so that their rollback() method
does not throw another exception.

Give savepoints another go on MySQL, can't get release working
however get support for basic round trip going

Fixes: #5327
Change-Id: Ia3cbbf56d4882fcc7980f90519412f1711fae74d

1 files changed, 22 insertions, 5 deletions

diff --git a/test/orm/test_transaction.py b/test/orm/test_transaction.py
index 78a62199a..22e7363b0 100644
--- a/test/orm/test_transaction.py
+++ b/test/orm/test_transaction.py
@@ -367,13 +367,25 @@ class SessionTransactionTest(fixtures.RemovesEvents, FixtureTest):
         sess.add(u)
         sess.flush()
         c1 = sess.connection(User)
+        dbapi_conn = c1.connection
+        assert dbapi_conn.is_valid
 
         sess.invalidate()
-        assert c1.invalidated
+
+        # Connection object is closed
+        assert c1.closed
+
+        # "invalidated" is not part of "closed" state
+        assert not c1.invalidated
+
+        # but the DBAPI conn (really ConnectionFairy)
+        # is invalidated
+        assert not dbapi_conn.is_valid
 
         eq_(sess.query(User).all(), [])
         c2 = sess.connection(User)
         assert not c2.invalidated
+        assert c2.connection.is_valid
 
     def test_subtransaction_on_noautocommit(self):
         User, users = self.classes.User, self.tables.users
@@ -859,7 +871,7 @@ class SessionTransactionTest(fixtures.RemovesEvents, FixtureTest):
         except Exception:
             trans2.rollback(_capture_exception=True)
         assert_raises_message(
-            sa_exc.InvalidRequestError,
+            sa_exc.PendingRollbackError,
             r"This Session's transaction has been rolled back due to a "
             r"previous exception during flush. To begin a new transaction "
             r"with this Session, first issue Session.rollback\(\). "
@@ -1001,7 +1013,7 @@ class SessionTransactionTest(fixtures.RemovesEvents, FixtureTest):
 
         for i in range(5):
             assert_raises_message(
-                sa_exc.InvalidRequestError,
+                sa_exc.PendingRollbackError,
                 "^This Session's transaction has been "
                 r"rolled back due to a previous exception "
                 "during flush. To "
@@ -1037,7 +1049,7 @@ class SessionTransactionTest(fixtures.RemovesEvents, FixtureTest):
 
         with expect_warnings(".*during handling of a previous exception.*"):
             session.begin_nested()
-            savepoint = session.connection()._transaction._savepoint
+            savepoint = session.connection()._nested_transaction._savepoint
 
             # force the savepoint to disappear
             session.connection().dialect.do_release_savepoint(
@@ -1708,7 +1720,12 @@ class SavepointTest(_LocalFixture):
         nested_trans._do_commit()
 
         is_(s.transaction, trans)
-        assert_raises(sa_exc.DBAPIError, s.rollback)
+
+        with expect_warnings("nested transaction already deassociated"):
+            # this previously would raise
+            # "savepoint "sa_savepoint_1" does not exist", however as of
+            # #5327 the savepoint already knows it's inactive
+            s.rollback()
 
         assert u1 not in s.new