[FIX] web: no more double discard dialog

This issue only occurred in community.
Steps to produce:
1) Create/Edit any record.
2) Change the menu using menu switcher
3) You will get the discard dialog at the instance and after some
   time it will also display another duplicate discard dialog.

So, we have one extra redundant discard dialog on menu switching.
It is working fine when we have dirty form and then click on the
breadcrumb or click on any internal child menu.

Task : 2312437

closes odoo/odoo#57359

X-original-commit: df37ce50e847e3489eb43d1ef6fc1bac6d6af333
Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>
Co-authored-by: Mohammed Shekha <msh@odoo.com>
Co-authored-by: Aaron Bohy <aab@odoo.com>

addons/web/static/src/js/views/basic/basic_controller.js

@@ -47,6 +47,10 @@ var BasicController = AbstractController.extend(FieldManagerMixin, {
         // operations to complete before checking if there are changes to
         // discard when discardChanges is called
         this.savingDef = Promise.resolve();
+        // discardingDef is used to ensure that we don't ask twice the user if
+        // he wants to discard changes, when 'canBeDiscarded' is called several
+        // times "in parallel"
+        this.discardingDef = null;
         this.viewId = params.viewId;
     },
     /**
@@ -78,21 +82,30 @@ var BasicController = AbstractController.extend(FieldManagerMixin, {
      */
     canBeDiscarded: function (recordID) {
         var self = this;
+        if (this.discardingDef) {
+            // discard dialog is already open
+            return this.discardingDef;
+        }
         if (!this.isDirty(recordID)) {
             return Promise.resolve(false);
         }
 
         var message = _t("The record has been modified, your changes will be discarded. Do you want to proceed?");
-        var def;
-        def = new Promise(function (resolve, reject) {
+        this.discardingDef = new Promise(function (resolve, reject) {
             var dialog = Dialog.confirm(self, message, {
                 title: _t("Warning"),
-                confirm_callback: resolve.bind(self, true),
-                cancel_callback: reject,
+                confirm_callback: () => {
+                    resolve(true);
+                    self.discardingDef = null;
+                },
+                cancel_callback: () => {
+                    reject();
+                    self.discardingDef = null;
+                },
             });
-            dialog.on('closed', def, reject);
+            dialog.on('closed', self.discardingDef, reject);
         });
-        return def;
+        return this.discardingDef;
     },
     /**
      * Ask the renderer if all associated field widget are in a valid state for

addons/web/static/tests/views/form_tests.js

@@ -8625,6 +8625,38 @@ QUnit.module('Views', {
         form.destroy();
     });
 
+    QUnit.test('call canBeRemoved twice', async function (assert) {
+        assert.expect(4);
+
+        const form = await createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form><field name="display_name"/><field name="foo"/></form>',
+            res_id: 1,
+            viewOptions: {
+                mode: 'edit',
+            },
+        });
+
+        assert.containsOnce(form, '.o_form_editable');
+        await testUtils.fields.editInput(form.$('.o_field_widget[name=foo]'), 'some value');
+
+        form.canBeRemoved();
+        await testUtils.nextTick();
+        assert.containsOnce(document.body, '.modal');
+
+        form.canBeRemoved();
+        await testUtils.nextTick();
+        assert.containsOnce(document.body, '.modal');
+
+        await testUtils.dom.click($('.modal .modal-footer .btn-secondary'));
+
+        assert.containsNone(document.body, '.modal');
+
+        form.destroy();
+    });
+
     QUnit.test('domain returned by onchange is cleared on discard', async function (assert) {
         assert.expect(4);