QML module is not installed ( QT5.15, Qmake)

Question

I'm facing the issue of "module is not installed" when trying to import a new custom QML module to project. I have tried many solutions from the internet and ChatGPT, but I haven't found any correct answer for my case.

This is my project structure.

<ProjectRoot>
  |-- frontend/
      |-- AlphaQ/
          |-- Styles/
              |-- Style1.0.qml
              |-- qmldir
          |-- Themes/
              |-- Themes1.0.qml
              |-- qmldir
      |-- main.qml
      |-- Home.qml
      |-- Home.js
      |-- qtquickcontrols2.conf
  |-- src/
      |-- main.cpp
  |-- qml.qrc

qml.qrc's content:

<RCC>
    <qresource prefix="/">
        <file>frontend/main.qml</file>
        <file>frontend/Home.qml</file>
        <file>frontend/Home.js</file>
        <file alias="qtquickcontrols2.conf">frontend/qtquickcontrols2.conf</file>
        <file alias="icons/send40x40.png">frontend/icons/send40x40.png</file>
        <file>frontend/AlphaQ/Styles/Style1.0.qml</file>
        <file>frontend/AlphaQ/Themes/Themes1.0.qml</file>
        <file>frontend/AlphaQ/Themes/qmldir</file>
        <file>frontend/AlphaQ/Styles/qmldir</file>
    </qresource>
</RCC>

frontend/AlphaQ/Styles/Style1.0.qml:

module AlphaQ.Styles
singleton Style 1.0 Style1.0.qml

frontend/AlphaQ/Themes/Themes1.0.qml:

module AlphaQ.Themes
singleton Themes 1.0 Themes1.0.qml

main.qml

import QtQuick 2.15
import QtQuick.Window 2.15

import AlphaQ.Styles 1.0

The problem can be solved by call this command inside main.cpp:

qmlRegisterSingletonType(QUrl("qrc:/frontend/AlphaQ/Styles/Style1.0.qml"), "AlphaQ.Styles", 1, 0, "StyleA");

But I'm expect the solution from qmldir, please help me find out what's wrong. Thanks

This list is what I have tried:

1. engine.addImportPath
2. set prefix AlphaQ.Styles in QRC
3. qmlRegisterSingletonType ( This fix my issue, but I expect other solutions)
4. set QML_IMPORT_PATH = $$PWD\frontend\

Answer 1

remove frontend/ from <file>frontend/*.qml</file> and add it to <qresource prefix="/">

like this:

<RCC>
<qresource prefix="/frontend/">
    <file>main.qml</file>
    <file>Home.qml</file>
    <file>Home.js</file>
    <file alias="qtquickcontrols2.conf">qtquickcontrols2.conf</file>
    <file alias="icons/send40x40.png">icons/send40x40.png</file>
    <file>AlphaQ/Styles/Style1.0.qml</file>
    <file>AlphaQ/Themes/Themes1.0.qml</file>
    <file>AlphaQ/Themes/qmldir</file>
    <file>AlphaQ/Styles/qmldir</file>
</qresource>

Or if you can move your qml.qrc to fontend directory and add

engine.addImportPath( ":/" );

to your main.cpp