QJSEngine, error #2 (Problem after Qt update)

mrjj

@SPlatten
hi
Is that code enough to see the issue ?
I have only Windows Os. Have you also seen it there ?

SPlatten

@mrjj, I don't have a machine running Windows anymore. That source should be enough for any reasonable coder to use the same and reproduce.

https://bugreports.qt.io/browse/QTBUG-83432

mrjj

@SPlatten
Ok super.

Sure but it lowers the number of people testing it as
one must make a project, alter the code a lot to make it compile
since its a member function.

alt text

when we have to change the code a lot to make it run , there is a chance we introduce other errors
or simply not test the same.

anyway, would you say this test it ?

void Test()
{
    QJSEngine *mspobjJSeng = new class QJSEngine();

    mspobjJSeng->installExtensions(
        QJSEngine::AllExtensions); //Added the tests below to illustrate it doesn't work, both error with 2

    QJSValue err;
    err = mspobjJSeng->evaluate("(print(1 + 2);)");

    if ( err.isError() ) {
        qDebug() << err.EvalError;
    }

    err = mspobjJSeng->evaluate("(console.log(1 + 2);");

    if ( err.isError() ) {
        qDebug() << err.EvalError;
    }
}

SPlatten

Sorry, I should have uploaded the example application I created when I posted the bug on the official site...

    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QDebug>

    int main(int argc, char *argv[]) {
        QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
        QGuiApplication app(argc, argv);
        QJSEngine test;
        test.installExtensions(QJSEngine::AllExtensions);
        QJSValue result = test.evaluate("(console.info(\"Hello World\");)");
        qDebug() << result.EvalError;
        return 0;
    }

mrjj

Hi
Ah, yes that was easier to test with.
Anyway, i also got error 2 for both examples on windows using
Qt 5.14.1

So this did use to work in other version or ?

mrjj

Hi
Tested some more.
i dont get the
" Indicates that console functions (console.log(), for example) should be installed."
error.

so the error 2 comes from not being a value i guess.

 auto text = R"(
                    function f(a, b) {
                      console.log("a is ", a, "b is ", b);
                    }
                    f(10,10);
                    )";
        QJSValue result = test.evaluate(text);

console seems to work.

js: a is  10 b is  10
2

so it does work for me on Win. No error about console.

SPlatten

My usage is similar I use console.info in a function and its not working, yes it was working in previous versions of Qt.

In my example even Hello World just a string doesn't work.

mrjj

@SPlatten

so it broke going from 5-14-1 to 5-14-2 ?
or what was your old version ?
Seems to work in 5.14.1 here on win.

SPlatten

Sorry I really can't answer that, here is an update, just tried this:

    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QDebug>

    int main(int argc, char *argv[]) {
        QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
        QGuiApplication app(argc, argv);
        QJSEngine test;
        test.installExtensions(QJSEngine::AllExtensions);
        QJSValue result;
        result = test.evaluate("console.log(123);");
        qDebug() << result.EvalError;
        result = test.evaluate("(console.log(456);)");
        qDebug() << result.EvalError;
        result = test.evaluate("(console.log(\"Hello World\");)");
        qDebug() << result.EvalError;
        return 0;
    }

The output from this was:

    QML debugging is enabled. Only use this in a safe environment.
    2020-04-10 13:15:53.563312+0100 scriptExample[1089:16542] QML Debugger: Waiting for connection on port 49396...
    2020-04-10 13:15:54.515935+0100 scriptExample[1089:16432] [js] 123
    2020-04-10 13:15:54.515978+0100 scriptExample[1089:16432] 2
    2020-04-10 13:15:54.516023+0100 scriptExample[1089:16432] 2
    2020-04-10 13:15:54.516132+0100 scriptExample[1089:16432] 2
    2020-04-10 13:15:54.671516+0100 scriptExample[1089:16432] QObject::connect: No such signal QCoreApplication::focusObjectChanged(QObject*)

Interestingly, removing the brackets surrounding the console.log call and it worked. The addition / requirement of brackets around the JavaScript is a fairly new addition.

Another edit, I changed the last console.log to:

    result = test.evaluate("function abc(t) { console.log(\"Hello World:\" + t);}abc(999);");
    qDebug() << result.EvalError;

Output:

    2020-04-10 13:23:59.005721+0100 scriptExample[1207:20216] [js] Hello World:999
    2020-04-10 13:23:59.005735+0100 scriptExample[1207:20216] 2

Notice that result.EvalError is still 2 even though the script was executed perfectly and the output was as desired.

My conclusion is that the issue seems to be related to the introduction of wrapping content in brackets.
if I remove the brackets from the console.log that displays Hello World, that also works.

SPlatten

There would seem to be multiple problems with QJSEngine, if I try to register a global then it must be wrapped in () or it fails:

    "({\"db\":\"test\",\"host\":\"localhost\",\"usr\":\"root\",\"pass\":\"123456\"})"

If it is left as:

    "{\"db\":\"test\",\"host\":\"localhost\",\"usr\":\"root\",\"pass\":\"123456\"}"

It fails with, EvalError: 2

It's not consistent, some things need to be wrapped in () or they fail others cannot be wrapped in () or they will fail, what is the reasoning for it and surely it would be better all round if the wrapping and handling of when or if to wrap in () was handled by the engine itself?

SPlatten

Trying alternate versions until I can find one that doesn't have this problem, so far I've tried:

5.14.2
5.13.2
5.12.8
5.12.2

Then there is quite a jump to versions available on the MaintenanceTool to 5.9.9, which I'm downloading now.

Qt 5.9.9 works, I'm getting different syntax errors now, but at least the fundamental stuff is now working. Hope this gives the Qt developers something to go on.

Yep, 5.9.9 definitely works.