QmlDesigner: Add function to locate import insertion point in QML text

This patch introduces `find_import_location`, which determines the
appropriate
location to insert a new `import` statement in a QML file. It scans the
header
section of the file, checks for existing imports, and avoids inserting
duplicates
when the target import already exists without an alias. The function
returns
an iterator pointing to the correct insertion point.

Change-Id: If1c55da7e56066b5395cf47f589e1e3566c119c6
Reviewed-by: Henning Gründl <henning.gruendl@qt.io>

src/plugins/qmldesigner/libs/qmldesignerutils/CMakeLists.txt

@@ -18,6 +18,7 @@ add_qtc_library(QmlDesignerUtils STATIC
     version.cpp version.h
     maputils.h
     stringutils.cpp stringutils.h
+    importutils.cpp importutils.h
 )
 
 extend_qtc_library(QmlDesignerUtils

src/plugins/qmldesigner/libs/qmldesignerutils/importutils.cpp

@@ -0,0 +1,48 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include "importutils.h"
+
+#include <QRegularExpression>
+
+#include <algorithm>
+#include <ranges>
+
+template<>
+inline constexpr bool std::ranges::enable_borrowed_range<QStringView> = true;
+template<>
+inline constexpr bool std::ranges::enable_view<QStringView> = true;
+
+namespace QmlDesigner::ImportUtils {
+
+using namespace Qt::StringLiterals;
+
+std::optional<QStringView::iterator> find_import_location(QStringView text, QStringView directory)
+{
+    const auto begin = text.begin();
+    const auto headerEnd = std::ranges::find(text, u'{');
+    QStringView header = {begin, headerEnd};
+    QStringView import{u"import"};
+
+    auto importRange = std::ranges::search(header.rbegin(),
+                                           header.rend(),
+                                           import.rbegin(),
+                                           import.rend());
+
+    if (importRange.empty())
+        return {begin};
+
+    auto endLine = std::ranges::find(importRange.begin().base(), headerEnd, u'\n');
+
+    QRegularExpression regex{uR"(^import\s+")"_s + directory + uR"("\s+(?!as))"_s};
+
+    if (regex.matchView({begin, endLine}).hasMatch())
+        return {};
+
+    if (endLine == text.end())
+        return {text.end()};
+
+    return std::make_optional<QStringView::iterator>(std::ranges::next(endLine));
+}
+
+} // namespace QmlDesigner::ImportUtils

src/plugins/qmldesigner/libs/qmldesignerutils/importutils.h

@@ -0,0 +1,16 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include "qmldesignerutils_global.h"
+
+#include <optional>
+#include <QStringView>
+
+namespace QmlDesigner::ImportUtils {
+
+QMLDESIGNERUTILS_EXPORT std::optional<QStringView::iterator> find_import_location(QStringView text,
+                                                                                  QStringView directory);
+
+} // namespace QmlDesigner::ImportUtils

tests/unit/tests/unittests/qmldesignerutils/CMakeLists.txt

@@ -4,4 +4,5 @@ extend_qtc_test(unittest
   SOURCES
     version-test.cpp
     stringutils-test.cpp
+    importutils-test.cpp
 )

tests/unit/tests/unittests/qmldesignerutils/importutils-test.cpp

@@ -0,0 +1,89 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include <googletest.h>
+
+#include <qmldesignerutils/importutils.h>
+
+namespace {
+
+using namespace Qt::StringLiterals;
+using QmlDesigner::ImportUtils::find_import_location;
+
+TEST(ImportUtils, begin_for_no_imports)
+{
+    auto content = QStringView{uR"("Item {})"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    ASSERT_THAT(found, content.begin());
+}
+
+TEST(ImportUtils, begin_for_imports_after_last_import)
+{
+    auto content = QStringView{u"import foo\n"
+                               u"import bar\n"
+                               u"\n"
+                               u"Item {}\n"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    QStringView rest{*found, content.end()};
+    ASSERT_THAT(rest, u"\nItem {}\n");
+}
+
+TEST(ImportUtils, skip_already_existing_directory_import)
+{
+    auto content = QStringView{u"import \"foo\"\n"
+                               u"import bar\n"
+                               u"\n"
+                               u"Item {}\n"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    ASSERT_THAT(found, std::nullopt);
+}
+
+TEST(ImportUtils, dont_already_existing_directory_import_with_as)
+{
+    auto content = QStringView{u"import \"foo\" as foo\n"
+                               u"import bar\n"
+                               u"\n"
+                               u"Item {}\n"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    QStringView rest{*found, content.end()};
+    ASSERT_THAT(rest, u"\nItem {}\n");
+}
+
+TEST(ImportUtils, ignore_import_properties)
+{
+    auto content = QStringView{u"import foo\n"
+                               u"import bar\n"
+                               u"\n"
+                               u"Item { import :}\n"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    QStringView rest{*found, content.end()};
+    ASSERT_THAT(rest, u"\nItem { import :}\n");
+}
+
+TEST(ImportUtils, handle_nothing_after_import)
+{
+    auto content = QStringView{u"import foo\n"
+                               u"import bar"};
+    QStringView directory = u"foo";
+
+    auto found = find_import_location(content, directory);
+
+    ASSERT_THAT(found, content.end());
+}
+
+} // namespace