formattexteditor: fix broken formatting

In case of unicode character, moving cursor relatively can result in
wrong placement of the cursor. Use absolute positions.

Fixes: QTCREATORBUG-28859
Change-Id: Idf68481861fc10c24b1eb330220fba92cadf560a
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/texteditor/formattexteditor.cpp

@@ -215,7 +215,7 @@ void updateEditorText(QPlainTextEdit *editor, const QString &text)
                     }
                 }
             }
-            cursor.movePosition(QTextCursor::Right, QTextCursor::KeepAnchor, d.text.size());
+            cursor.setPosition(cursor.position() + d.text.size(), QTextCursor::KeepAnchor);
             cursor.removeSelectedText();
             break;
         }
@@ -223,7 +223,7 @@ void updateEditorText(QPlainTextEdit *editor, const QString &text)
         case Diff::Equal:
             // Adjust cursor position
             charactersInfrontOfCursor -= d.text.size();
-            cursor.movePosition(QTextCursor::Right, QTextCursor::MoveAnchor, d.text.size());
+            cursor.setPosition(cursor.position() + d.text.size(), QTextCursor::MoveAnchor);
             break;
         }
     }
@@ -329,3 +329,56 @@ void formatEditorAsync(TextEditorWidget *editor, const Command &command, int sta
 }
 
 } // namespace TextEditor
+
+#ifdef WITH_TESTS
+#include <texteditorplugin.h>
+#include <QTest>
+
+namespace TextEditor::Internal {
+
+void TextEditorPlugin::testFormatting_data()
+{
+    QTest::addColumn<QString>("code");
+    QTest::addColumn<QString>("result");
+
+    {
+        QString code {
+            "import QtQuick\n\n"
+            "  Item {\n"
+            "     property string cat: [\"👩🏽‍🚒d👩🏽‍🚒d👩🏽‍🚒\"]\n"
+            "        property string dog: cat\n"
+            "}\n"
+        };
+
+        QString result {
+            "import QtQuick\n\n"
+            "Item {\n"
+            "    property string cat: [\"👩🏽‍🚒\"]\n"
+            "    property string dog: cat\n"
+            "}\n"
+        };
+
+        QTest::newRow("unicodeCharacterInFormattedCode") << code << result;
+    }
+}
+
+void TextEditorPlugin::testFormatting()
+{
+    QFETCH(QString, code);
+    QFETCH(QString, result);
+
+    QScopedPointer<TextEditorWidget> editor(new TextEditorWidget);
+    QVERIFY(editor.get());
+
+    QSharedPointer<TextDocument> doc(new TextDocument);
+    doc->setPlainText(code);
+    editor->setTextDocument(doc);
+
+    TextEditor::updateEditorText(editor.get(), result);
+
+    QCOMPARE(editor->toPlainText(), result);
+}
+
+} // namespace TextEditor::Internal
+
+#endif

src/plugins/texteditor/texteditorplugin.h

@@ -37,6 +37,9 @@ private slots:
 
     void testIndentationClean_data();
     void testIndentationClean();
+
+    void testFormatting_data();
+    void testFormatting();
 #endif
 };