- revert the change first made in a6fe4dc, as we are now generalizing

the warning here to all safe_reraise() cases in Python 2.
- Revisiting :ticket:`2696`, first released in 1.0.10, which attempts to
work around Python 2's lack of exception context reporting by emitting
a warning for an exception that was interrupted by a second exception
when attempting to roll back the already-failed transaction; this
issue continues to occur for MySQL backends in conjunction with a
savepoint that gets unexpectedly lost, which then causes a
"no such savepoint" error when the rollback is attempted, obscuring
what the original condition was.

The approach has been generalized to the Core "safe
reraise" function which takes place across the ORM and Core in any
place that a transaction is being rolled back in response to an error
which occurred trying to commit, including the context managers
provided by :class:`.Session` and :class:`.Connection`, and taking
place for operations such as a failure on "RELEASE SAVEPOINT".
Previously, the fix was only in place for a specific path within
the ORM flush/commit process; it now takes place for all transational
context managers as well.
fixes #2696

1 files changed, 33 insertions, 1 deletions

diff --git a/test/base/test_utils.py b/test/base/test_utils.py
index 6d162ff4d..53dbc12f9 100644
--- a/test/base/test_utils.py
+++ b/test/base/test_utils.py
@@ -3,7 +3,7 @@ import sys
 
 from sqlalchemy import util, sql, exc, testing
 from sqlalchemy.testing import assert_raises, assert_raises_message, fixtures
-from sqlalchemy.testing import eq_, is_, ne_, fails_if, mock
+from sqlalchemy.testing import eq_, is_, ne_, fails_if, mock, expect_warnings
 from sqlalchemy.testing.util import picklers, gc_collect
 from sqlalchemy.util import classproperty, WeakSequence, get_callable_argspec
 from sqlalchemy.sql import column
@@ -2192,6 +2192,38 @@ class ReraiseTest(fixtures.TestBase):
             if testing.requires.python3.enabled:
                 is_(moe.__cause__, me)
 
+    @testing.requires.python2
+    def test_safe_reraise_py2k_warning(self):
+        class MyException(Exception):
+            pass
+
+        class MyOtherException(Exception):
+            pass
+
+        m1 = MyException("exc one")
+        m2 = MyOtherException("exc two")
+
+        def go2():
+            raise m2
+
+        def go():
+            try:
+                raise m1
+            except:
+                with util.safe_reraise():
+                    go2()
+
+        with expect_warnings(
+            "An exception has occurred during handling of a previous "
+            "exception.  The previous exception "
+            "is:.*MyException.*exc one"
+        ):
+            try:
+                go()
+                assert False
+            except MyOtherException:
+                pass
+
 
 class TestClassProperty(fixtures.TestBase):