[PyQt] Bug with empty string in QWebPage::javaScriptPrompt

Sat Jun 14 20:59:02 BST 2014

I think I found a bug with QWebPage::javaScriptPrompt using
Qt/PyQt 5.2.1, Qt runtime 5.3.0 and Python 3.4.

When overriding QWebPage::javaScriptPrompt and returning an empty
string, javascript gets some random RAM content back it seems. This
also might be a security issue...

When I run super().javaScriptPrompt, (True, '') is returned when I
enter an empty string in the dialog as well, so what I return seems to
be correct.

Example script which simply gets a value via prompt(), returns it to
javascript, and prints it to the terminal via alert(), then garbage is
printed to the terminal:

# ======

from PyQt5.QtWidgets import QApplication
from PyQt5.QtWebKitWidgets import QWebPage, QWebView

HTML = """
<html>
    <head>
        <script type="text/javascript">
            function prompter() {
                var reply = prompt("Test", "")
                alert( "Answer: " + reply)
            }
        </script>
    </head>
    <body>
        <input type="button" onclick="prompter()" value="Test">
    </body>
</html>
"""

class WebPage(QWebPage):

    def javaScriptPrompt(self, frame, msg, default):
        return True, ''

    def javaScriptAlert(self, frame, msg):
        print("alert: {}".format(msg.encode('ASCII', errors='backslashreplace')))
        return

app = QApplication([])
view = QWebView()
page = WebPage()
view.setPage(page)
view.setHtml(HTML)
view.show()
app.exec_()

# ======

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