[FIX] web: fix js data during consecutive sequence of resequence moves

Let x_1, ..., x_a, x_{a+1}, ..., x_{a+k}, x_{a+k+1}, ..., x_{n} be a record
sequence ordered by its 'sequence' field.
Suppose the reordering occurs between elements x_{a+k} and x_{a+1}.
If the subsequence x_1, ..., x_a is ordered, then it does not change.
This is also true of the subsequence x_{a+k+1}, ..., x_{n}.
The resquence function makes exactly this assumption, and only sends the server
the subsequence x_{a+1}, ..., x_{a+k} to update its 'sequence' field.
The update of x is done as follows: it is index + offset, where index is the
position of x in the subsequence, and offset is the 'sequence' of the first
element of the sequence (i.e. x_{a+1}.sequence).

It is easy to see that we need another hypothesis: that the sequence numbers are
unique. To show it, suppose that the sequence of x_1, ..., x_a is 0, then all
x_{a+1}, ..., x_{a+k} have sequence 1, and lastly all x_{a+k}, x_{a+k+1}, ...,
x_{n} have sequence 2. Then after the call to the server resequence, the
subsequence x_{a+1}, ..., x_{a+k} would have sequence numbers 1, 2,..., k.
Since the x_{a+k+1}, ..., x_{n} subsequence have 'sequence' value 1, this would
obviously be incorrect.

We fix the reordering of the data in the js frontend to be consistent with
what is done by the server.
Note that this is only pertinent for sequences of reordering moves, since
otherwise the data comes directly from the server.

opw 1867049

1 files changed, 7 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 7621fe35446..16f77b7954c 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -894,8 +894,14 @@ var BasicModel = AbstractModel.extend({
                 params: params,
             })
             .then(function () {
+                var offset = options.offset ? options.offset : 0;
+                var old_data = data.data.slice();
                 data.data = _.sortBy(data.data, function (d) {
-                    return _.indexOf(resIDs, self.localData[d].res_id);
+                    if (_.contains(resIDs, self.localData[d].res_id)) {
+                        return _.indexOf(resIDs, self.localData[d].res_id) + offset;
+                    } else {
+                        return _.indexOf(old_data, d);
+                    }
                 });
                 data.res_ids = [];
                 _.each(data.data, function (d) {