- The :class:`.exc.StatementError` or DBAPI-related subclass

now can accomodate additional information about the "reason" for
the exception; the :class:`.Session` now adds some detail to it
when the exception occurs within an autoflush.  This approach
is taken as opposed to combining :class:`.FlushError` with
a Python 3 style "chained exception" approach so as to maintain
compatibility both with Py2K code as well as code that already
catches ``IntegrityError`` or similar.

1 files changed, 11 insertions, 2 deletions

diff --git a/lib/sqlalchemy/exc.py b/lib/sqlalchemy/exc.py
index 3c0c6c365..93722fe99 100644
--- a/lib/sqlalchemy/exc.py
+++ b/lib/sqlalchemy/exc.py
@@ -219,6 +219,10 @@ class StatementError(SQLAlchemyError):
         self.statement = statement
         self.params = params
         self.orig = orig
+        self.detail = []
+
+    def add_detail(self, msg):
+        self.detail.append(msg)
 
     def __reduce__(self):
         return self.__class__, (self.args[0], self.statement,
@@ -227,8 +231,13 @@ class StatementError(SQLAlchemyError):
     def __str__(self):
         from sqlalchemy.sql import util
         params_repr = util._repr_params(self.params, 10)
-        return ' '.join((SQLAlchemyError.__str__(self),
-                         repr(self.statement), repr(params_repr)))
+
+        return ' '.join([
+                            "(%s)" % det for det in self.detail
+                        ] + [
+                            SQLAlchemyError.__str__(self),
+                             repr(self.statement), repr(params_repr)
+                        ])
 
     def __unicode__(self):
         return self.__str__()