plugins exts UPDATE ext callback for data node validation

Fixes #1908
diff --git a/src/parser_json.c b/src/parser_json.c
index 4babe34..82275b6 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -1413,7 +1413,10 @@
         }
 
         /* add/correct flags */
-        lyd_parse_set_data_flags(*node, &(*node)->meta, (struct lyd_ctx *)lydctx, ext);
+        LY_CHECK_RET(lyd_parse_set_data_flags(*node, &(*node)->meta, (struct lyd_ctx *)lydctx, ext));
+
+        /* store for ext instance node validation, if needed */
+        LY_CHECK_RET(lyd_validate_node_ext(*node, &lydctx->ext_node));
     } else if (ret == LY_ENOT) {
         /* parse it again as an opaq node */
         ret = lydjson_parse_opaq(lydctx, name, name_len, prefix, prefix_len, parent, status, status, first_p, node);