py/objobject: Add object.__delattr__ function.

Similar to object.__setattr__.

py/objobject.c

@@ -77,6 +77,23 @@ STATIC mp_obj_t object___setattr__(mp_obj_t self_in, mp_obj_t attr, mp_obj_t val
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_3(object___setattr___obj, object___setattr__);
+
+STATIC mp_obj_t object___delattr__(mp_obj_t self_in, mp_obj_t attr) {
+    if (!mp_obj_is_instance_type(mp_obj_get_type(MP_OBJ_TO_PTR(self_in)))) {
+        mp_raise_TypeError("arg must be user-type");
+    }
+
+    if (!mp_obj_is_str(attr)) {
+        mp_raise_TypeError(NULL);
+    }
+
+    mp_obj_instance_t *self = MP_OBJ_TO_PTR(self_in);
+    if (mp_map_lookup(&self->members, attr, MP_MAP_LOOKUP_REMOVE_IF_FOUND) == NULL) {
+        mp_raise_msg(&mp_type_AttributeError, "no such attribute");
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(object___delattr___obj, object___delattr__);
 #endif
 
 STATIC const mp_rom_map_elem_t object_locals_dict_table[] = {
@@ -88,6 +105,7 @@ STATIC const mp_rom_map_elem_t object_locals_dict_table[] = {
     #endif
     #if MICROPY_PY_DELATTR_SETATTR
     { MP_ROM_QSTR(MP_QSTR___setattr__), MP_ROM_PTR(&object___setattr___obj) },
+    { MP_ROM_QSTR(MP_QSTR___delattr__), MP_ROM_PTR(&object___delattr___obj) },
     #endif
 };
 

tests/basics/class_delattr_setattr.py

@@ -69,6 +69,9 @@ class C:
     def __setattr__(self, attr, value):
         print(attr, "=", value)
 
+    def __delattr__(self, attr):
+        print("del", attr)
+
 c = C()
 c.a = 5
 try:
@@ -86,3 +89,25 @@ try:
     object.__setattr__(c, 5, 5)
 except TypeError:
     print("TypeError")
+
+
+# test object.__delattr__
+del c.a
+print(c.a)
+
+object.__delattr__(c, "a")
+try:
+    print(c.a)
+except AttributeError:
+    print("AttributeError")
+
+super(C, c).__delattr__("b")
+try:
+    print(c.b)
+except AttributeError:
+    print("AttributeError")
+
+try:
+    object.__delattr__(c, "c")
+except AttributeError:
+    print("AttributeError")