diff options
Diffstat (limited to 'lib/sqlalchemy/sql/visitors.py')
| -rw-r--r-- | lib/sqlalchemy/sql/visitors.py | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/lib/sqlalchemy/sql/visitors.py b/lib/sqlalchemy/sql/visitors.py index 24ada8d9f..7b729bf7f 100644 --- a/lib/sqlalchemy/sql/visitors.py +++ b/lib/sqlalchemy/sql/visitors.py @@ -26,6 +26,7 @@ http://techspot.zzzeek.org/2008/01/23/expression-transformations/ from collections import deque from .. import util import operator +from .. import exc __all__ = ['VisitableType', 'Visitable', 'ClauseVisitor', 'CloningVisitor', 'ReplacingCloningVisitor', 'iterate', @@ -70,14 +71,24 @@ def _generate_dispatch(cls): getter = operator.attrgetter("visit_%s" % visit_name) def _compiler_dispatch(self, visitor, **kw): - return getter(visitor)(self, **kw) + try: + meth = getter(visitor) + except AttributeError: + raise exc.UnsupportedCompilationError(visitor, cls) + else: + return meth(self, **kw) else: # The optimization opportunity is lost for this case because the # __visit_name__ is not yet a string. As a result, the visit # string has to be recalculated with each compilation. def _compiler_dispatch(self, visitor, **kw): visit_attr = 'visit_%s' % self.__visit_name__ - return getattr(visitor, visit_attr)(self, **kw) + try: + meth = getattr(visitor, visit_attr) + except AttributeError: + raise exc.UnsupportedCompilationError(visitor, cls) + else: + return meth(self, **kw) _compiler_dispatch.__doc__ = \ """Look for an attribute named "visit_" + self.__visit_name__ |