qt_add_qml_module: Set QT_QML_MODULE_QML_FILES correctly

A QML module might not actually contain any QML files at all (in case of
a pure C++ module). In such a case, we so far ended up with
QT_QML_MODULE_QML_FILES being set to "-NOTOUND", which later is
problematic for qt_query_qml_module.

We already have code in place to cover that issue for some variables,
just not for QML_FILES. The code is now amended to handle it, too.
Moreover, the code block is moved to the end of the function. This
ensures that the code for setting a variable always comes before the
code ensuring that it is set – which would not have been the case for
QML_FILES if it had stayed at its old position.

Pick-to: 6.5
Task-number: QTBUG-111946
Change-Id: Ib4501bb4a617b2174ad89e116588aa51353cb17f
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/qml/Qt6QmlMacros.cmake

@@ -532,21 +532,6 @@ Check https://doc.qt.io/qt-6/qt-cmake-policy-qtp0001.html for policy details."
         )
     endif()
 
-    set(ensure_set_properties
-        QT_QML_MODULE_PLUGIN_TYPES_FILE
-        QT_QML_MODULE_RESOURCES       # Original files as provided by the project (absolute)
-        QT_QML_MODULE_RESOURCE_PATHS  # By qmlcachegen (resource paths)
-        QT_QMLCACHEGEN_DIRECT_CALLS
-        QT_QMLCACHEGEN_EXECUTABLE
-        QT_QMLCACHEGEN_ARGUMENTS
-    )
-    foreach(prop IN LISTS ensure_set_properties)
-        get_target_property(val ${target} ${prop})
-        if("${val}" MATCHES "-NOTFOUND$")
-            set_target_properties(${target} PROPERTIES ${prop} "")
-        endif()
-    endforeach()
-
     if(NOT arg_NO_GENERATE_QMLTYPES)
         set(type_registration_extra_args "")
         if(arg_NAMESPACE)
@@ -707,6 +692,23 @@ Check https://doc.qt.io/qt-6/qt-cmake-policy-qtp0001.html for policy details."
         set(${arg_OUTPUT_TARGETS} ${output_targets} PARENT_SCOPE)
     endif()
 
+
+    set(ensure_set_properties
+        QT_QML_MODULE_PLUGIN_TYPES_FILE
+        QT_QML_MODULE_QML_FILES
+        QT_QML_MODULE_RESOURCES       # Original files as provided by the project (absolute)
+        QT_QML_MODULE_RESOURCE_PATHS  # By qmlcachegen (resource paths)
+        QT_QMLCACHEGEN_DIRECT_CALLS
+        QT_QMLCACHEGEN_EXECUTABLE
+        QT_QMLCACHEGEN_ARGUMENTS
+    )
+    foreach(prop IN LISTS ensure_set_properties)
+        get_target_property(val ${target} ${prop})
+        if("${val}" MATCHES "-NOTFOUND$")
+            set_target_properties(${target} PROPERTIES ${prop} "")
+        endif()
+    endforeach()
+
 endfunction()
 
 if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)

tests/auto/cmake/qmlquery/CMakeLists.txt

@@ -8,3 +8,4 @@ find_package(Qt6 REQUIRED COMPONENTS Qml)
 set(CMAKE_AUTOMOC TRUE)
 
 add_subdirectory(My/Things)
+add_subdirectory(My/OtherThings)

tests/auto/cmake/qmlquery/My/OtherThings/CMakeLists.txt

@@ -0,0 +1,28 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+qt_policy(SET QTP0001 NEW)
+
+function(verify_result keyword expected actual)
+    if(NOT "${actual}" STREQUAL "${expected}")
+        message(SEND_ERROR
+            "  Expected ${keyword}: ${expected}\n"
+            "  Actual   ${keyword}: ${actual}"
+        )
+    endif()
+endfunction()
+
+qt_add_qml_module(MyOtherThings
+    URI My.OtherThings
+    SOURCES
+        test.h test.cpp
+)
+
+qt_query_qml_module(MyOtherThings
+    QML_FILES qml_files2
+    RESOURCES resources2
+)
+
+# empty resources and files
+verify_result(RESOURCES "${resources2}" "")
+verify_result(QML_FILES "${qml_files2}" "")

tests/auto/cmake/qmlquery/My/OtherThings/test.cpp

@@ -0,0 +1,3 @@
+#include "test.h"
+
+Test::Test() {}

tests/auto/cmake/qmlquery/My/OtherThings/test.h

@@ -0,0 +1,18 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef TEST_H
+#define TEST_H
+
+#include <QtQml/qqml.h>
+#include <QObject>
+
+class Test : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+public:
+    Test();
+};
+
+#endif // TEST_H