[REF] web: don't destroy twice a widget's children

Widget class indirectly inherits from ParentedMixin (through
PropertiesMixin).

The Widget's children are destroyed in both the ParentedMixin and the
Widget's own destroy() method.

This commit prevents from trying to destroy already destroyed children
and specifically from looping again on those children (resulting into a
minor performance improvement).

closes odoo/odoo#32174

Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/web/static/src/js/core/mixins.js

@@ -98,8 +98,8 @@ var ParentedMixin = {
      * resource it could have reserved.
      */
     destroy : function () {
-        _.each(this.getChildren(), function (el) {
-            el.destroy();
+        this.getChildren().forEach(function (child) {
+            child.destroy();
         });
         this.setParent(undefined);
         this.__parentedDestroyed = true;

addons/web/static/src/js/core/widget.js

@@ -172,13 +172,10 @@ var Widget = core.Class.extend(mixins.PropertiesMixin, ServicesMixin, {
      * destroying itself.
      */
     destroy: function () {
-        this.getChildren().forEach(function (child) {
-            child.destroy();
-        });
+        mixins.PropertiesMixin.destroy.call(this);
         if (this.$el) {
             this.$el.remove();
         }
-        mixins.PropertiesMixin.destroy.call(this);
     },
 
     //--------------------------------------------------------------------------

addons/web/static/tests/core/widget_tests.js

@@ -468,6 +468,20 @@ QUnit.module('core', {}, function () {
         slowWillStartPromise.resolve();
     });
 
+    QUnit.test("don't destroy twice widget's children", function (assert) {
+        assert.expect(2);
+
+        var parent = new Widget();
+        var child = new (Widget.extend({
+            destroy: function () {
+                assert.step('destroy');
+            }
+        }))(parent);
+
+        parent.destroy();
+        assert.verifySteps(['destroy'], "child should have been detroyed only once");
+    });
+
 });
 
 });