py: Support object __getattr__, __delattr__ and __setattr__ methods

py/mpconfig.h

@@ -636,6 +636,12 @@ typedef double mp_float_t;
 #define MICROPY_PY_DESCRIPTORS (0)
 #endif
 
+// Whether to support object (__getattr__, __delattr__ and __setattr__)
+// This costs some code size and makes all load attrs and store attrs slow
+#ifndef MICROPY_PY_ATTRS_METHODS
+#define MICROPY_PY_ATTRS_METHODS (0)
+#endif
+
 // Support for async/await/async for/async with
 #ifndef MICROPY_PY_ASYNC_AWAIT
 #define MICROPY_PY_ASYNC_AWAIT (1)

py/objobject.c

@@ -59,13 +59,48 @@ STATIC mp_obj_t object___new__(mp_obj_t cls) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(object___new___fun_obj, object___new__);
 STATIC MP_DEFINE_CONST_STATICMETHOD_OBJ(object___new___obj, MP_ROM_PTR(&object___new___fun_obj));
 
+#if MICROPY_PY_ATTRS_METHODS
+STATIC mp_obj_t object___setattr__(mp_obj_t self_in, mp_obj_t attr_in, mp_obj_t value) {
+    mp_map_lookup(mp_obj_dict_get_map(self_in), MP_OBJ_NEW_QSTR(mp_obj_str_get_qstr(attr_in)), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;
+    return value;
+}
+MP_DEFINE_CONST_FUN_OBJ_3(object___setattr___obj, object___setattr__);
+
+STATIC mp_obj_t object___getattr__(mp_obj_t self_in, mp_obj_t attr_in) {
+    qstr attr = mp_obj_str_get_qstr(attr_in);
+    mp_map_elem_t *elem = mp_map_lookup(mp_obj_dict_get_map(self_in), MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP);
+    if (elem == NULL) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_AttributeError,
+            "'%s' object has no attribute '%q'",
+            mp_obj_get_type_str(self_in), attr));
+    }
+    return elem->value;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(object___getattr___obj, object___getattr__);
+
+STATIC mp_obj_t object___delattr__(mp_obj_t self_in, mp_obj_t attr_in) {
+    mp_map_lookup(mp_obj_dict_get_map(self_in), MP_OBJ_NEW_QSTR(mp_obj_str_get_qstr(attr_in)), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(object___delattr___obj, object___delattr__);
+#endif
+
 STATIC const mp_rom_map_elem_t object_locals_dict_table[] = {
     #if MICROPY_CPYTHON_COMPAT
     { MP_ROM_QSTR(MP_QSTR___init__), MP_ROM_PTR(&object___init___obj) },
     #endif
     #if MICROPY_CPYTHON_COMPAT
     { MP_ROM_QSTR(MP_QSTR___new__), MP_ROM_PTR(&object___new___obj) },
     #endif
+    #if (MICROPY_CPYTHON_COMPAT && MICROPY_PY_ATTRS_METHODS)
+    { MP_ROM_QSTR(MP_QSTR___delattr__), MP_ROM_PTR(&object___delattr___obj) },
+    #endif
+    #if (MICROPY_CPYTHON_COMPAT && MICROPY_PY_ATTRS_METHODS)
+    { MP_ROM_QSTR(MP_QSTR___getattr__), MP_ROM_PTR(&object___getattr___obj) },
+    #endif
+    #if (MICROPY_CPYTHON_COMPAT && MICROPY_PY_ATTRS_METHODS)
+    { MP_ROM_QSTR(MP_QSTR___setattr__), MP_ROM_PTR(&object___setattr___obj) },
+    #endif
 };
 
 STATIC MP_DEFINE_CONST_DICT(object_locals_dict, object_locals_dict_table);

py/objtype.c

@@ -626,10 +626,39 @@ STATIC bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t val
 
     if (value == MP_OBJ_NULL) {
         // delete attribute
+        #if MICROPY_PY_ATTRS_METHODS
+        // try __delattr__ first
+        if (attr != MP_QSTR___delattr__) {
+            mp_obj_t attr_delattr_method[3];
+            mp_load_method_maybe(self_in, MP_QSTR___delattr__, attr_delattr_method);
+            if (attr_delattr_method[0] != MP_OBJ_NULL) {
+                // __delattr__ exists, call it and return its result
+                attr_delattr_method[2] = MP_OBJ_NEW_QSTR(attr);
+                mp_call_method_n_kw(1, 0, attr_delattr_method);
+                return true;
+            }
+        }
+        #endif
+
         mp_map_elem_t *elem = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
         return elem != NULL;
     } else {
         // store attribute
+        #if MICROPY_PY_ATTRS_METHODS
+        // try __setattr__ first
+        if (attr != MP_QSTR___setattr__) {
+            mp_obj_t attr_setattr_method[4];
+            mp_load_method_maybe(self_in, MP_QSTR___setattr__, attr_setattr_method);
+            if (attr_setattr_method[0] != MP_OBJ_NULL) {
+                // __setattr__ exists, call it and return its result
+                attr_setattr_method[2] = MP_OBJ_NEW_QSTR(attr);
+                attr_setattr_method[3] = value;
+                mp_call_method_n_kw(2, 0, attr_setattr_method);
+                return true;
+            }
+        }
+        #endif
+
         mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;
         return true;
     }