Safely get attributes in attr completion

thomasballinger · thomasballinger · commit 39b22ca94928 · 2015-12-11T08:39:37.000-05:00
diff --git a/bpython/autocomplete.py b/bpython/autocomplete.py
@@ -707,7 +707,7 @@ def attr_lookup(obj, expr, attr):
     n = len(attr)
     for word in words:
         if method_match(word, n, attr) and word != "__builtins__":
-            attr_obj = getattr(obj, word)  # scary!
+            attr_obj = inspection.safe_get_attribute(obj, word)
             matches.append(_callable_postfix(attr_obj, "%s.%s" % (expr, word)))
     return matches
 
diff --git a/bpython/inspection.py b/bpython/inspection.py
@@ -282,6 +282,43 @@ def is_callable(obj):
     return callable(obj)
 
 
+class AttributeIsEmptySlot(object):
+    pass
+
+
+def safe_get_attribute(obj, attr):
+    """Gets attributes without triggering descriptors on new-style clases
+
+    Returns AttributeIsEmptySlot if requested attribute does not have a value,
+    but is a slot entry.
+    """
+    if not is_new_style(obj):
+        raise ValueError("%r is not a new-style class or object" % obj)
+    to_look_through = (obj.mro()
+                       if hasattr(obj, 'mro')
+                       else [obj] + type(obj).mro())
+
+    for cls in to_look_through:
+        if hasattr(cls, '__dict__') and attr in cls.__dict__:
+            return cls.__dict__[attr]
+        elif hasattr(cls, '__slots__') and attr in cls.__slots__:
+            try:
+                return getattr(cls, attr)
+            except AttributeError:
+                return AttributeIsEmptySlot
+
+    raise AttributeError()
+
+def get_attribute(obj, attr):
+    cls = type(obj)
+    for cls in [obj] + cls.mro():
+        if attr in cls.__dict__:
+            return cls.__dict__[attr]
+            break
+    raise AttributeError
+
+
+
 get_encoding_re = LazyReCompile(r'coding[:=]\s*([-\w.]+)')
 
 
diff --git a/bpython/test/test_autocomplete.py b/bpython/test/test_autocomplete.py
@@ -277,7 +277,8 @@ def __getattr__(self, attr):
     def test_descriptor_attributes_not_run(self):
         com = autocomplete.AttrCompletion()
         self.assertSetEqual(com.matches(2, 'a.', locals_={'a': Properties()}),
-                            set(['a.asserts_when_called']))
+                            set(['a.b', 'a.a', 'a.method(',
+                                 'a.asserts_when_called']))
 
 
 class TestArrayItemCompletion(unittest.TestCase):
diff --git a/bpython/test/test_inspection.py b/bpython/test/test_inspection.py
@@ -135,5 +135,50 @@ def test_get_source_file(self):
         self.assertEqual(encoding, 'utf-8')
 
 
+class A(object):
+    a = 'a'
+
+class B(A):
+    b = 'b'
+
+class Property(object):
+    @property
+    def prop(self):
+        raise AssertionError('Property __get__ executed')
+
+class Slots(object):
+    __slots__ = ['s1', 's2']
+
+class TestSafeGetAttribute(unittest.TestCase):
+
+    def test_lookup_on_object(self):
+        a = A()
+        a.x = 1
+        self.assertEquals(inspection.safe_get_attribute(a, 'x'), 1)
+        self.assertEquals(inspection.safe_get_attribute(a, 'a'), 'a')
+        b = B()
+        b.y = 2
+        self.assertEquals(inspection.safe_get_attribute(b, 'y'), 2)
+        self.assertEquals(inspection.safe_get_attribute(b, 'a'), 'a')
+        self.assertEquals(inspection.safe_get_attribute(b, 'b'), 'b')
+
+    def test_avoid_running_properties(self):
+        p = Property()
+        self.assertEquals(inspection.safe_get_attribute(p, 'prop'),
+                          Property.prop)
+
+    def test_raises_on_old_style_class(self):
+        class Old: pass
+        with self.assertRaises(ValueError):
+            inspection.safe_get_attribute(Old, 'asdf')
+
+    def test_lookup_with_slots(self):
+        s = Slots()
+        s.s1 = 's1'
+        self.assertEquals(inspection.safe_get_attribute(s, 's1'), 's1')
+        self.assertEquals(inspection.safe_get_attribute(s, 's2'),
+                          inspection.AttributeIsEmptySlot)
+
+
 if __name__ == '__main__':
     unittest.main()
