py: Be more restrictive binding self when looking up instance attrs.

dpgeorge · dpgeorge · commit 78913211a953 · 2015-12-26T12:41:31.000Z
When looking up and extracting an attribute of an instance, some attributes must bind self as the first argument to make a working method call. Previously to this patch, any attribute that was callable had self bound as the first argument. But Python specs require the check to be more restrictive, and only functions, closures and generators should have self bound as the first argument Addresses issue adafruit#1675.
diff --git a/py/runtime.c b/py/runtime.c
@@ -947,7 +947,11 @@ void mp_convert_member_lookup(mp_obj_t self, const mp_obj_type_t *type, mp_obj_t
     } else if (MP_OBJ_IS_TYPE(member, &mp_type_type)) {
         // Don't try to bind types (even though they're callable)
         dest[0] = member;
-    } else if (mp_obj_is_callable(member)) {
+    } else if (MP_OBJ_IS_FUN(member)
+        || (MP_OBJ_IS_OBJ(member)
+            && (((mp_obj_base_t*)MP_OBJ_TO_PTR(member))->type->name == MP_QSTR_closure
+                || ((mp_obj_base_t*)MP_OBJ_TO_PTR(member))->type->name == MP_QSTR_generator))) {
+        // only functions, closures and generators objects can be bound to self
         #if MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG
         if (self == MP_OBJ_NULL && mp_obj_get_type(member) == &mp_type_fun_builtin) {
             // we extracted a builtin method without a first argument, so we must
diff --git a/tests/basics/class_bind_self.py b/tests/basics/class_bind_self.py
@@ -0,0 +1,54 @@
+# test for correct binding of self when accessing attr of an instance
+
+class A:
+    def __init__(self, arg):
+        self.val = arg
+    def __str__(self):
+        return 'A.__str__ ' + str(self.val)
+    def __call__(self, arg):
+        return 'A.__call__', arg
+    def foo(self, arg):
+        return 'A.foo', self.val, arg
+
+def make_closure(x_in):
+    x = x_in
+    def closure(y):
+        return x, y is c
+    return closure
+
+class C:
+    # these act like methods and bind self
+
+    def f1(self, arg):
+        return 'C.f1', self is c, arg
+    f2 = lambda self, arg: ('C.f2', self is c, arg)
+    f3 = make_closure('f3') # closure
+    def f4(self, arg): # generator
+        yield self is c, arg
+
+    # these act like simple variables and don't bind self
+
+    f5 = int # builtin type
+    f6 = abs # builtin function
+    f7 = A # user type
+    f8 = A(8) # user instance which is callable
+    f9 = A(9).foo # user bound method
+
+c = C()
+print(c.f1(1))
+print(c.f2(2))
+print(c.f3())
+print(next(c.f4(4)))
+print(c.f5(5))
+#print(c.f6(-6)) not working in uPy
+print(c.f7(7))
+print(c.f8(8))
+print(c.f9(9))
+
+# not working in uPy
+#class C(list):
+#    # this acts like a method and binds self
+#    f1 = list.extend
+#c = C()
+#c.f1([3, 1, 2])
+#print(c)
