[FIX] web: wait many2many tags' fetches for rendering

Before this commit, we don't assure fetch's deferreds were resolved to
return _readGroup. Thus, in some conditions, kanban was rendered before
records data was updated so many2many tags could be missing.
Now, we return _readGroup when fetch's deferreds were resolved.

Task #1910805

closes odoo/odoo#29508

1 files changed, 6 insertions, 3 deletions

diff --git a/addons/web/static/src/js/views/basic/basic_model.js b/addons/web/static/src/js/views/basic/basic_model.js
index 8266b1dee42..fecbaa5b90c 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -4289,9 +4289,12 @@ var BasicModel = AbstractModel.extend({
                     }
                     return list;
                 }).then(function () {
-                    self._fetchX2ManysSingleBatch(list);
-                    self._fetchReferencesSingleBatch(list);
-                    return list;
+                    var fetchingDefs = [];
+                    fetchingDefs.push(self._fetchX2ManysSingleBatch(list));
+                    fetchingDefs.push(self._fetchReferencesSingleBatch(list));
+                    return $.when.apply($, fetchingDefs).then(function () {
+                        return list;
+                    });
                 });
             });
     },