Reworked internal exception raises that emit

a rollback() before re-raising, so that the stack
trace is preserved from sys.exc_info() before entering
the rollback.  This so that the traceback is preserved
when using coroutine frameworks which may have switched
contexts before the rollback function returns.
[ticket:2703]

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/sqlalchemy/util/compat.py b/lib/sqlalchemy/util/compat.py
index 2a0f06f8e..0f0a2f674 100644
--- a/lib/sqlalchemy/util/compat.py
+++ b/lib/sqlalchemy/util/compat.py
@@ -140,3 +140,29 @@ else:
     def b(s):
         return s
 
+
+if py3k:
+    def reraise(tp, value, tb=None, cause=None):
+        if cause is not None:
+            value.__cause__ = cause
+        if value.__traceback__ is not tb:
+            raise value.with_traceback(tb)
+        raise value
+
+    def raise_from_cause(exception, exc_info):
+        exc_type, exc_value, exc_tb = exc_info
+        reraise(type(exception), exception, tb=exc_tb, cause=exc_value)
+else:
+    exec("""def reraise(tp, value, tb=None, cause=None):
+        raise tp, value, tb
+    """)
+
+    def raise_from_cause(exception, exc_info):
+        # not as nice as that of Py3K, but at least preserves
+        # the code line where the issue occurred
+        exc_type, exc_value, exc_tb = exc_info
+        reraise(type(exception), exception, tb=exc_tb)
+
+
+
+