Qbs: Artifacts of rules are not listed in the project tree

import qbs
import qbs.TextFile

CppApplication {
    type: "application"
    files: "main.cpp"
    Rule {
        inputs: ["qbs"]
        multiplex: true
        outputFileTags: ["cpp"]
        outputArtifacts: [
            {
                fileTags: "cpp",
                filePath: "foo.cpp",
            }
        ]

        prepare: {
            var cmd = new JavaScriptCommand();
            cmd.description = "Generating " + output.filePath;
            cmd.sourceCode = function() {
                new TextFile(output.filePath, TextFile.WriteOnly);
            }

            return cmd;
        }
    }
}