[FIX] web: prevent useless discard dialog from showing up

Here is a scenario that could cause an issue:
- open a form view with a many2one
- click on edit button
- click on small external button for many2one. this opens a modal form
  view
- click on save in the modal (without changing anything)
- click on save in the main record
- exit form view. this opens a discard dialog

There were two issues here:
- saving the modal dialog automatically marks the many2one field as changed.
  This was necessary to force reloading the data, because editing a sub value
  in the modal form view could have changed the display_name of the manyone
  field.  However, this is not necessary when no change was done.
- when saving a record, the _isDirty flag was reset to false only if an
  actual rpc was done.  However, it may happen that the flag is set to
  dirty (for example, when modifying a value inside a many2one), but the
  main record has no changed fields.

In this commit, we also remove the on_save handler in the
formviewdialog.  This is a small refactoring in a stable version, but no code
currently use it, and I believe that it will make the code much easier
to maintain (the previous code was really awkward), so I think that the
tradeoff is acceptable.

1 files changed, 5 insertions, 3 deletions

diff --git a/addons/web/static/src/js/fields/relational_fields.js b/addons/web/static/src/js/fields/relational_fields.js
index 19f2728a3ae..c9e6f218895 100644
--- a/addons/web/static/src/js/fields/relational_fields.js
+++ b/addons/web/static/src/js/fields/relational_fields.js
@@ -502,9 +502,11 @@ var FieldMany2One = AbstractField.extend({
                     title: _t("Open: ") + self.string,
                     view_id: view_id,
                     readonly: !self.can_write,
-                    on_saved: function () {
-                        self._setValue(self.value.data, {forceChange: true});
-                        self.trigger_up('reload', {db_id: self.value.id});
+                    on_saved: function (record, changed) {
+                        if (changed) {
+                            self._setValue(self.value.data, {forceChange: true});
+                            self.trigger_up('reload', {db_id: self.value.id});
+                        }
                     },
                 }).open();
             });