Add direction and uselist properties

sqlalchemy_utils/path.py

@@ -1,5 +1,6 @@
 import sqlalchemy as sa
 from sqlalchemy.orm.attributes import InstrumentedAttribute
+from sqlalchemy.util.langhelpers import symbol
 from .utils import str_coercible
 
 
@@ -105,9 +106,22 @@ class AttrPath(object):
             if el is element:
                 return index
 
+    @property
+    def direction(self):
+        symbols = [part.property.direction for part in self.parts]
+        if symbol('MANYTOMANY') in symbols:
+            return symbol('MANYTOMANY')
+        elif symbol('MANYTOONE') in symbols and symbol('ONETOMANY') in symbols:
+            return symbol('MANYTOMANY')
+        return symbols[0]
+
+    @property
+    def uselist(self):
+        return any(part.property.uselist for part in self.parts)
+
     def __getitem__(self, slice):
         result = self.parts[slice]
-        if isinstance(result, list):
+        if isinstance(result, list) and result:
             if result[0] is self.parts[0]:
                 class_ = self.class_
             else:

tests/test_path.py

@@ -1,6 +1,7 @@
 import six
-from pytest import mark
 import sqlalchemy as sa
+from pytest import mark
+from sqlalchemy.util.langhelpers import symbol
 from sqlalchemy_utils.path import Path, AttrPath
 from tests import TestCase
 
@@ -41,6 +42,17 @@ class TestAttrPath(TestCase):
         self.Section = Section
         self.SubSection = SubSection
 
+    @mark.parametrize(
+        ('class_', 'path', 'direction'),
+        (
+            ('SubSection', 'section', symbol('MANYTOONE')),
+        )
+    )
+    def test_direction(self, class_, path, direction):
+        assert (
+            AttrPath(getattr(self, class_), path).direction == direction
+        )
+
     def test_invert(self):
         path = ~ AttrPath(self.SubSection, 'section.document')
         assert path.parts == [