- Added support for the case of the misbehaving DBAPI that has

pep-249 exception names linked to exception classes of an entirely
different name, preventing SQLAlchemy's own exception wrapping from
wrapping the error appropriately.
The SQLAlchemy dialect in use needs to implement a new
accessor :attr:`.DefaultDialect.dbapi_exception_translation_map`
to support this feature; this is implemented now for the py-postgresql
dialect.
fixes #3421

3 files changed, 23 insertions, 2 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index af310c450..7ebe39bbf 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -1261,7 +1261,8 @@ class Connection(Connectable):
                 exc.DBAPIError.instance(statement,
                                         parameters,
                                         e,
-                                        self.dialect.dbapi.Error),
+                                        self.dialect.dbapi.Error,
+                                        dialect=self.dialect),
                 exc_info
             )
         self._reentrant_error = True
@@ -1277,7 +1278,8 @@ class Connection(Connectable):
                     parameters,
                     e,
                     self.dialect.dbapi.Error,
-                    connection_invalidated=self._is_disconnect)
+                    connection_invalidated=self._is_disconnect,
+                    dialect=self.dialect)
             else:
                 sqlalchemy_exception = None
 
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 763e85f82..9330a602c 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -157,6 +157,15 @@ class DefaultDialect(interfaces.Dialect):
 
     reflection_options = ()
 
+    dbapi_exception_translation_map = util.immutabledict()
+    """mapping used in the extremely unusual case that a DBAPI's
+    published exceptions don't actually have the __name__ that they
+    are linked towards.
+
+    .. versionadded:: 1.0.5
+
+    """
+
     def __init__(self, convert_unicode=False,
                  encoding='utf-8', paramstyle=None, dbapi=None,
                  implicit_returning=None,
diff --git a/lib/sqlalchemy/engine/interfaces.py b/lib/sqlalchemy/engine/interfaces.py
index 2dd192162..73a8b4635 100644
--- a/lib/sqlalchemy/engine/interfaces.py
+++ b/lib/sqlalchemy/engine/interfaces.py
@@ -150,6 +150,16 @@ class Dialect(object):
       This will prevent types.Boolean from generating a CHECK
       constraint when that type is used.
 
+    dbapi_exception_translation_map
+       A dictionary of names that will contain as values the names of
+       pep-249 exceptions ("IntegrityError", "OperationalError", etc)
+       keyed to alternate class names, to support the case where a
+       DBAPI has exception classes that aren't named as they are
+       referred to (e.g. IntegrityError = MyException).   In the vast
+       majority of cases this dictionary is empty.
+
+       .. versionadded:: 1.0.5
+
     """
 
     _has_events = False