QAbstractOAuth2::refreshToken() returns an empty string when the QOAuth2AuthorizationCodeFlow::granted signal is emitted.

[Hossein2000]

In the code below, the authentication process is performed by QOAuth2AuthorizationCodeFlow.
This code works correctly to get the access token, but it does not return the refresh token.

#include "qoauth2test.h"
QOAuth2Test::QOAuth2Test(QObject *parent) : QObject(parent)
{
    // Launch browser for authorization request
    connect(&google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser,
            &QDesktopServices::openUrl);
    // Receive answer from authorization request process
    connect(&google, &QOAuth2AuthorizationCodeFlow::granted, this, &QOAuth2Test::onGranted);

    QString authUri = "https://accounts.google.com/o/oauth2/v2/auth";
    QString clientId = "XXXX";
    QString tokenUri = "https://accounts.google.com/o/oauth2/token";
    QString clientSecret = "XXXX";
    QString scope = "https://www.googleapis.com/auth/drive";
    quint16 port = 8080;
    google.setAuthorizationUrl(authUri);
    google.setClientIdentifier(clientId);
    google.setAccessTokenUrl(tokenUri);
    google.setClientIdentifierSharedKey(clientSecret);
    google.setScope(scope);

    google.setModifyParametersFunction([&](QAbstractOAuth::Stage stage, QVariantMap* parameters) {
        // Percent-decode the "code" parameter so Google can match it
        if (stage == QAbstractOAuth::Stage::RequestingAccessToken)
        {
            QByteArray code = parameters->value("code").toByteArray();
            (*parameters)["code"] = QUrl::fromPercentEncoding(code);
        }
    });

    auto replyHandler = new QOAuthHttpServerReplyHandler(port, this);
    google.setReplyHandler(replyHandler);
}

void QOAuth2Test::grant()
{
    google.grant();
}

void QOAuth2Test::onGranted()
{
    accessToken = google.token();
    qInfo() << "access Token:"<< accessToken;
    refreshToken = google.refreshToken();
    qInfo() << "refresh Token:"<< refreshToken;
}

Please tell me if anyone knows the solution.
Thank you.

[Hossein2000]

I found the answer
You need to replace

connect(&google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser,
            &QDesktopServices::openUrl);

with

connect(this->google, &QOAuth2AuthorizationCodeFlow::authorizeWithBrowser, [=](QUrl url) {
        QUrlQuery query(url);

        query.addQueryItem("prompt", "consent");      // Param required to get data everytime
        query.addQueryItem("access_type", "offline"); // Needed for Refresh Token (as AccessToken expires shortly)
        url.setQuery(query);
        QDesktopServices::openUrl(url);
    });

[SGaist]

Hi and welcome to devnet,

Glad you found a solution and thanks for sharing !

Would you mind explaining how you got the solution ?

[Hossein2000]

@SGaist
Thanks . you're welcome
I stumbled this webpage accidentally, where Mr. Chilarai Mushahary had done exactly what I was looking for.