Add a _proxyImpl helper classpr/92

formalchemy does the following:

        if isinstance(self._impl, ScalarAttributeImpl) or self._impl.__class__.__name__ == '_ProxyImpl': # ProxyImpl is a one-off class for each synonym, can't import it
            # normal property, mapped to a single column from the main table
            prop = getattr(self._property, '_proxied_property', None)
            if prop is None:
                prop = self._property
            return tuple(prop.local_columns)

With this patch, this test can be replaced with

		if isinstance(self._impl, (ScalarAttributeImpl,ProxyImpl):
            …

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/descriptor_props.py b/lib/sqlalchemy/orm/descriptor_props.py
index 9ecc9bb62..c4d6aac27 100644
--- a/lib/sqlalchemy/orm/descriptor_props.py
+++ b/lib/sqlalchemy/orm/descriptor_props.py
@@ -18,6 +18,9 @@ from ..sql import expression
 from . import properties
 from . import query
 
+class ProxyImpl(object):
+	"""A helper class for detecting whether an attribute is a proxy"""
+	pass
 
 class DescriptorProperty(MapperProperty):
     """:class:`.MapperProperty` which proxies access to a
@@ -28,7 +31,7 @@ class DescriptorProperty(MapperProperty):
     def instrument_class(self, mapper):
         prop = self
 
-        class _ProxyImpl(object):
+        class _ProxyImpl(ProxyImpl):
             accepts_scalar_loader = False
             expire_missing = True
             collection = False