[FIX] web: m2o+o2m in o2m onchange no lose data

Steps:

- open a modal form view from tree view first line and make a change
- open a modal from the second line and make a change
- open the second line back: the change were lost

In a given number of conditions (a many2one inside the form view, there
is a one2many in the form view not inside the tree view, ....) this
happened because:

- when we save the first line, we get onchange data for the second one
- this onchange data can't be applied before second line is loaded, but
  it is saved so it can be applied if second line is ever opened
- when the second line is opened the saved change is applied => OK
- when the second line is opened a second time the saved change is
  applied again, possibly overwriting posterious change => BAD

With this changeset, when the record with unapplied onchange is loaded
for the first time, the unapplied onchange is applied only once.

Added test without the change failed with:

- only 1 turtle for second partner (result: 0 not 1)
- second partner turtle is Michelangelo (result: "" not "Michelangelo")

opw-1846820
closes #28644

1 files changed, 5 insertions, 5 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 50f1f13808b..b9832996de5 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -1439,6 +1439,11 @@ var BasicModel = AbstractModel.extend({
                 record._rawChanges[name] = val;
                 return;
             }
+            if (record._rawChanges[name]) {
+                // if previous _rawChanges exists, clear them since the field is now knwon
+                // and restoring outdated onchange over posterious change is wrong
+                delete record._rawChanges[name];
+            }
             var oldValue = name in record._changes ? record._changes[name] : record.data[name];
             var id;
             if (field.type === 'many2one') {
@@ -2552,11 +2557,6 @@ var BasicModel = AbstractModel.extend({
                     relationField: field.relation_field,
                     viewType: view ? view.type : fieldInfo.viewType,
                 });
-                // set existing changes to the list
-                if (record._changes && record._changes[fieldName]) {
-                    list._changes = self.localData[record._changes[fieldName]]._changes;
-                    record._changes[fieldName] = list.id;
-                }
                 record.data[fieldName] = list.id;
                 if (!fieldInfo.__no_fetch) {
                     var def = self._readUngroupedList(list).then(function () {