[FIX] web: properly refetch x2manys in some cases

Consider the following situation: a form view with a one2many which
contains sub x2many fields (for example a m2m_tags). Suppose that the
one2many has more than 40 records.  Before this commit, trying to delete
one of these records caused a crash.

The reason is that when we delete a record, we need to reload the
missing records in the one2many field.  We actually do that with a
_readUngroupedList.  However, the _readUngroupedList method did not
process x2many fields, so the information stored in the datapoints was
'raw', and the rest of the web client expected it to be a datapoint.

To reproduce the issue in the testing environment, i had to use
onchanges and a readonly attrs, to reach a situation where a crash could
occur.  This shows that, while the issue is critical, it was not totally
trivial to be impacted by it.

1 files changed, 3 insertions, 1 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 fcd9785b9a5..ed18be034af 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -1573,7 +1573,9 @@ var BasicModel = AbstractModel.extend({
         return $.when.apply($, defs).then(function () {
             // ensure to fetch up to 'limit' records (may be useful if records of
             // the current page have been removed)
-            return self._readUngroupedList(list);
+            return self._readUngroupedList(list).then(function () {
+                return self._fetchX2ManysBatched(list);
+            });
         });
     },
     /**