QbsProjectManager: Support QML designer import paths

Task-number: QTCREATORBUG-20810
Change-Id: I1f096124f94d2c9f4ad51373bb39a212a108799f
Reviewed-by: hjk <hjk@qt.io>

doc/src/qtquick/creator-only/qtquick-modules-with-plugins.qdoc

@@ -175,7 +175,8 @@
 
     If you want to use a different module in the Design mode than in your actual
     application for example to mockup C++ items, then you can use \c{QML_DESIGNER_IMPORT_PATH}
-    in the \c{.pro} file.
+    in the \c{.pro} file (for qmake projects), or declare and set the property
+    qmlDesignerImportPaths in your product (for Qbs projects).
     Modules in the import paths defined in \c{QML_DESIGNER_IMPORT_PATH} will be
     used only in the Design mode.
     For an example, see \l {Qt Quick Controls 2 - Contact List}.

src/plugins/qbsprojectmanager/qbsproject.cpp

@@ -188,6 +188,22 @@ ProjectImporter *QbsProject::projectImporter() const
     return m_importer;
 }
 
+QVariant QbsProject::additionalData(Id id, const Target *target) const
+{
+    if (id == "QmlDesignerImportPath") {
+        const qbs::Project qbsProject = m_qbsProjects.value(const_cast<Target *>(target));
+        const qbs::ProjectData projectData = qbsProject.isValid()
+                ? qbsProject.projectData() : qbs::ProjectData();
+        QStringList designerImportPaths;
+        foreach (const qbs::ProductData &product, projectData.allProducts()) {
+            designerImportPaths << product.properties()
+                                   .value("qmlDesignerImportPaths").toStringList();
+        }
+        return designerImportPaths;
+    }
+    return Project::additionalData(id, target);
+}
+
 QStringList QbsProject::filesGeneratedFrom(const QString &sourceFile) const
 {
     QStringList generated;

src/plugins/qbsprojectmanager/qbsproject.h

@@ -135,6 +135,7 @@ private:
 
     void projectLoaded() override;
     ProjectExplorer::ProjectImporter *projectImporter() const override;
+    QVariant additionalData(Core::Id id, const ProjectExplorer::Target *target) const final;
 
     static bool ensureWriteableQbsFile(const QString &file);