[FIX] web: FieldOne2Many: re-activate 'Add an item'

The 'Add an item' button of one2many editable lists is deactivated
once clicked (since rev. f9a1241) to prevent concurrent record
creation. It is re-activated when the record has been created.
Unfortunately, it might happen that the record is actually not
created, so in this case the button is never re-activated.

This happens for example on the customer invoice form view, if
the user tries to add a line before selecting a partner.

addons/web/static/src/js/fields/abstract_field.js

@@ -351,12 +351,13 @@ var AbstractField = Widget.extend({
      * @param {Object} [options]
      * @param {boolean} [options.forceChange=false] if true, the change event will be
      *   triggered even if the new value is the same as the old one
+     * @returns {Deferred}
      */
     _setValue: function (value, options) {
         // we try to avoid doing useless work, if the value given has not
         // changed.  Note that we compare the unparsed values.
         if (this.lastSetValue === value || (this.value === false && value === '')) {
-            return;
+            return $.when();
         }
         this.lastSetValue = value;
         try {
@@ -364,18 +365,22 @@ var AbstractField = Widget.extend({
             this._isValid = true;
         } catch (e) {
             this._isValid = false;
-            return;
+            return $.Deferred().reject();
         }
         if (!(options && options.forceChange) && this._isSameValue(value)) {
-            return;
+            return $.when();
         }
+        var def = $.Deferred();
         var changes = {};
         changes[this.name] = value;
         this.trigger_up('field_changed', {
             dataPointID: this.dataPointID,
             changes: changes,
             viewType: this.viewType,
+            onSuccess: def.resolve.bind(def),
+            onFailure: def.reject.bind(def),
         });
+        return def;
     },
 
     //--------------------------------------------------------------------------

addons/web/static/src/js/fields/relational_fields.js

@@ -964,7 +964,6 @@ var FieldOne2Many = FieldX2Many.extend({
                     var index = self.editable === 'top' ? 0 : self.value.data.length - 1;
                     var newID = self.value.data[index].id;
                     self.renderer.editRecord(newID);
-                    self.creatingRecord = false;
                 }
             }
         });
@@ -1014,6 +1013,7 @@ var FieldOne2Many = FieldX2Many.extend({
      *   in the kanban view
      */
     _onAddRecord: function (ev) {
+        var self = this;
         // we don't want interference with the components upstream.
         ev.stopPropagation();
 
@@ -1023,10 +1023,11 @@ var FieldOne2Many = FieldX2Many.extend({
                 this._setValue({
                     operation: 'CREATE',
                     position: this.editable,
+                }).always(function () {
+                    self.creatingRecord = false;
                 });
             }
         } else {
-            var self = this;
             this._openFormDialog({
                 on_saved: function (record) {
                     self._setValue({ operation: 'ADD', id: record.id });

addons/web/static/src/js/views/field_manager_mixin.js

@@ -99,7 +99,9 @@ var FieldManagerMixin = {
         // subrecord's form view), otherwise it bubbles up to the main form view
         // but its model doesn't have any data related to the given dataPointID
         event.stopPropagation();
-        this._applyChanges(event.data.dataPointID, event.data.changes, event);
+        this._applyChanges(event.data.dataPointID, event.data.changes, event)
+            .done(event.data.onSuccess || function () {})
+            .fail(event.data.onFailure || function () {});
     },
     /**
      * Some widgets need to trigger a reload of their data.  For example, a

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

@@ -3907,6 +3907,60 @@ QUnit.module('relational_fields', {
         form.destroy();
     });
 
+    QUnit.test('editable list: onchange that returns a warning', function (assert) {
+        assert.expect(5);
+
+        this.data.turtle.onchanges = {
+            display_name: function () {},
+        };
+
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form string="Partners">' +
+                    '<field name="turtles">' +
+                        '<tree editable="bottom">' +
+                            '<field name="display_name"/>' +
+                        '</tree>' +
+                    '</field>' +
+                '</form>',
+            res_id: 1,
+            mockRPC: function (route, args) {
+                if (args.method === 'onchange') {
+                    assert.step(args.method);
+                    return $.when({
+                        value: {},
+                        warning: {
+                            title: "Warning",
+                            message: "You must first select a partner"
+                        },
+                    });
+                }
+                return this._super.apply(this, arguments);
+            },
+            viewOptions: {
+                mode: 'edit',
+            },
+            intercepts: {
+                warning: function () {
+                    assert.step('warning');
+                },
+            },
+        });
+
+        // add a line (this should trigger an onchange and a warning)
+        form.$('.o_field_x2many_list_row_add a').click();
+
+        // check if 'Add an item' still works (this should trigger an onchange
+        // and a warning again)
+        form.$('.o_field_x2many_list_row_add a').click();
+
+        assert.verifySteps(['onchange', 'warning', 'onchange', 'warning']);
+
+        form.destroy();
+    });
+
     QUnit.module('FieldMany2Many');
 
     QUnit.test('many2many kanban: edition', function (assert) {