py/modbuiltins: Make built-in dir support the __dir__ special method.

If MICROPY_PY_ALL_SPECIAL_METHODS is enabled then dir() will now delegate
to the special method __dir__ if the object it is listing has this method.

1 files changed, 7 insertions, 0 deletions

diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index bc99f8261..0d511338b 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -190,6 +190,13 @@ STATIC mp_obj_t mp_builtin_dir(size_t n_args, const mp_obj_t *args) {
             mp_obj_t dest[2];
             mp_load_method_protected(args[0], i, dest, false);
             if (dest[0] != MP_OBJ_NULL) {
+                #if MICROPY_PY_ALL_SPECIAL_METHODS
+                // Support for __dir__: see if we can dispatch to this special method
+                // This relies on MP_QSTR__dir__ being first after MP_QSTR_
+                if (i == MP_QSTR___dir__ && dest[1] != MP_OBJ_NULL) {
+                    return mp_call_method_n_kw(0, 0, dest);
+                }
+                #endif
                 mp_obj_list_append(dir, MP_OBJ_NEW_QSTR(i));
             }
         }