Fixed part of issue #110: accessing from context a property raising an exception.

HISTORY.rst

 History
 =======
 
+0.5.3 (TBD)
+-----------
+
+* Bugfix: exceptions no longer swallowed when accessing from context a
+  property that raises an exception (issue #110).
+
 0.5.2 (2012-05-03)
 ------------------
 

pystache/context.py

@@ -55,8 +55,15 @@ def _get_value(context, key):
         # types like integers and strings as objects (cf. issue #81).
         # Instances of user-defined classes on the other hand, for example,
         # are considered objects by the test above.
-        if hasattr(context, key):
+        try:
             attr = getattr(context, key)
+        except AttributeError:
+            # TODO: distinguish the case of the attribute not existing from
+            #   an AttributeError being raised by the call to the attribute.
+            #   See the following issue for implementation ideas:
+            #     http://bugs.python.org/issue7559
+            pass
+        else:
             # TODO: consider using EAFP here instead.
             #   http://docs.python.org/glossary.html#term-eafp
             if callable(attr):

pystache/tests/test_context.py

@@ -147,6 +147,26 @@ class GetValueTests(unittest.TestCase, AssertIsMixin):
         self.assertEqual(item["foo"], "bar")
         self.assertNotFound(item, "foo")
 
+    def test_object__property__raising_exception(self):
+        """
+        Test getting a property that raises an exception.
+
+        """
+        class Foo(object):
+
+            @property
+            def bar(self):
+                return 1
+
+            @property
+            def baz(self):
+                raise ValueError("test")
+
+        foo = Foo()
+        self.assertEqual(_get_value(foo, 'bar'), 1)
+        self.assertNotFound(foo, 'missing')
+        self.assertRaises(ValueError, _get_value, foo, 'baz')
+
     ### Case: the item is an instance of a built-in type.
 
     def test_built_in_type__integer(self):