[FIX] web: editable list: setRowMode returns a deferred

This function should return a deferred, as indicated in the
docstring. However, in some cases, it doesn't. It then crashed
as the FieldX2Many tries to call done() on undefined.

This happens for instance on the customer invoice form view:
create a new record, select a partner, add a line, select a
product, directly click on the invoice date field (this will
trigger an onchange which will totally override the value of the
one2many). The FielX2Many calls setRowMode to switch the edited
row back to readonly, but this row doesn't exist anymore as the
one2many value has been overriden by the onchange, so setRowMode
wrongly returns nothing, and it crashes.

addons/web/static/src/js/views/list/list_editable_renderer.js

@@ -155,7 +155,7 @@ ListRenderer.include({
         var self = this;
         var rowIndex = _.findIndex(this.state.data, {id: recordID});
         if (rowIndex < 0) {
-            return;
+            return $.when();
         }
         var editMode = (mode === 'edit');
         var record = this.state.data[rowIndex];

addons/web/static/tests/fields/relational_fields_tests.js

@@ -3852,6 +3852,61 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('editable list: value reset by an onchange', function (assert) {
+        // this test reproduces a subtle behavior that may occur in a form view:
+        // the user adds a record in a one2many field, and directly clicks on a
+        // datetime field of the form view which has an onchange, which totally
+        // overrides the value of the one2many (commands 5 and 0). The handler
+        // that switches the edited row to readonly is then called after the
+        // new value of the one2many field is applied (the one returned by the
+        // onchange), so the row that must go to readonly doesn't exist anymore.
+        assert.expect(2);
+
+        this.data.partner.onchanges = {
+            datetime: function (obj) {
+                obj.turtles = [[5], [0, 0, {display_name: 'new'}]];
+            },
+        };
+
+        var def;
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form string="Partners">' +
+                    '<field name="datetime"/>' +
+                    '<field name="turtles">' +
+                        '<tree editable="bottom">' +
+                            '<field name="display_name"/>' +
+                        '</tree>' +
+                    '</field>' +
+                '</form>',
+            mockRPC: function (route, args) {
+                var result = this._super.apply(this, arguments);
+                if (args.method === 'onchange') {
+                    return $.when(def).then(_.constant(result));
+                }
+                return result;
+            },
+        });
+
+        // trigger the two onchanges
+        form.$('.o_field_x2many_list_row_add a').click();
+        form.$('.o_data_row .o_field_widget').val('a name').trigger('input');
+        def = $.Deferred();
+        form.$('.o_datepicker_input').click(); // focusout o2m and set value to today
+
+        // resolve the onchange def
+        def.resolve();
+
+        assert.strictEqual(form.$('.o_data_row').length, 1,
+            "should have one record in the o2m");
+        assert.strictEqual(form.$('.o_data_row .o_data_cell').text(), 'new',
+            "should be the record created by the onchange");
+
+        form.destroy();
+    });
+
     QUnit.module('FieldMany2Many');
 
     QUnit.test('many2many kanban: edition', function (assert) {