XWIKI-24806: TextAreaImageUploadIT is flickering and its missing edit-mode cleanup fails the rest of AllIT (#6309)

* Discard the unsaved changes after each test, so that a failure no longer leaves an armed
  beforeunload handler that blocks every test running after it in the shared browser session.
* Add CKEditor#discardUnsavedChanges() to the page objects, marking every editor instance on the
  page as clean. This is what arms the leave confirmation for the comment, the annotation and the
  in-place property, all edited on a view page where there is no edit mode to leave.
* Leave the edit mode for the object editor, which asks for confirmation based on its own form state.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 879250a)

Author: vmassol

xwiki-platform-core/xwiki-platform-ckeditor/xwiki-platform-ckeditor-test/xwiki-platform-ckeditor-test-pageobjects/src/main/java/org/xwiki/ckeditor/test/po/CKEditor.java

@@ -170,4 +170,18 @@ public void executeOnEditedContent(Runnable runnable)
             }
         }
     }
+
+    /**
+     * Marks every CKEditor instance on the current page as clean, so that leaving the page doesn't ask the user to
+     * confirm that they want to discard their changes. Meant to be called when cleaning up after a test that may have
+     * been interrupted in the middle of an edit: the confirmation dialog would otherwise block the next navigation,
+     * including the navigation done by the tests that come after in the same browser session.
+     *
+     * @since 18.8.0RC1
+     */
+    public static void discardUnsavedChanges()
+    {
+        getUtil().getDriver()
+            .executeScript("Object.values(window.CKEDITOR?.instances ?? {}).forEach(editor => editor.resetDirty());");
+    }
 }

xwiki-platform-core/xwiki-platform-edit/xwiki-platform-edit-test/xwiki-platform-edit-test-docker/src/test/it/org/xwiki/edit/test/ui/TextAreaImageUploadIT.java

@@ -19,6 +19,7 @@
  */
 package org.xwiki.edit.test.ui;
 
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Order;
 import org.junit.jupiter.api.Test;
@@ -86,6 +87,23 @@ void beforeAll(TestUtils testUtils) throws Exception
         testUtils.addClassProperty(CLASS_REFERENCE, PROPERTY_NAME, "TextArea");
     }
 
+    @AfterEach
+    void discardUnsavedChanges(TestUtils testUtils)
+    {
+        // A test failing in the middle of an edit leaves the page with unsaved changes, so the next navigation shows
+        // the leave confirmation. All the tests of AllIT share a single browser session, so that dialog blocks every
+        // test that comes after, in this class and in the other nested ones. Discarding the changes here keeps a
+        // failure contained to the test that caused it.
+
+        // The comment, the annotation and the in-place property are edited on a view page, where there is no edit
+        // mode to leave: the leave confirmation comes from the CKEditor instances themselves being dirty.
+        CKEditor.discardUnsavedChanges();
+
+        // The object editor asks for confirmation based on its own form state, which only leaving the edit mode
+        // resets. Done after the editors are marked clean, so that leaving doesn't trigger the dialog itself.
+        testUtils.maybeLeaveEditMode();
+    }
+
     /**
      * Upload an image while editing a TextArea property in the object editor, using basically the same setup as
      * {@code TextAreaIT}.