extmod/vfs_posix_file: Don't create file object unless open succeeds.

When passing in already open file handle integer, don't
enable the "handle close" finaliser.

Signed-off-by: Andrew Leech <[email protected]>

extmod/vfs_posix_file.c

@@ -63,7 +63,6 @@ STATIC void vfs_posix_file_print(const mp_print_t *print, mp_obj_t self_in, mp_p
 }
 
 mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_obj_t mode_in) {
-    mp_obj_vfs_posix_file_t *o = m_new_obj_with_finaliser(mp_obj_vfs_posix_file_t);
     const char *mode_s = mp_obj_str_get_str(mode_in);
 
     int mode_rw = 0, mode_x = 0;
@@ -92,18 +91,21 @@ mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_
         }
     }
 
-    o->base.type = type;
-
     mp_obj_t fid = file_in;
 
     if (mp_obj_is_small_int(fid)) {
+        // When opening an existing file description, don't close it on deletion
+        mp_obj_vfs_posix_file_t *o = m_new_obj(mp_obj_vfs_posix_file_t);
+        o->base.type = type;
         o->fd = MP_OBJ_SMALL_INT_VALUE(fid);
         return MP_OBJ_FROM_PTR(o);
     }
 
     const char *fname = mp_obj_str_get_str(fid);
     int fd;
     MP_HAL_RETRY_SYSCALL(fd, open(fname, mode_x | mode_rw, 0644), mp_raise_OSError(err));
+    mp_obj_vfs_posix_file_t *o = m_new_obj_with_finaliser(mp_obj_vfs_posix_file_t);
+    o->base.type = type;
     o->fd = fd;
     return MP_OBJ_FROM_PTR(o);
 }