LayoutTests/js/dom/error-stack-data-url-truncation.html

<html>
<head>
<script src="../../resources/js-test.js"></script>
</head>
<body>
<p id="description"></p>
<div id="console"></div>
<script>
description("Tests that a data: URL over 1024 characters is cut down in a stack frame, that the cut avoids %XX escapes, and that short URLs and other schemes are left alone.");

window.jsTestIsAsync = true;

const limit = 1024;

// Makes a module whose data: URL is exactly totalLength characters.
// percentAt puts a %20 escape at that index.
function makeModuleURL(totalLength, percentAt)
{
    const prefix = "data:text/javascript,export%20function%20mk()%7Breturn%20new%20Error('t')%7D%3B%2F%2F";
    let url = prefix;
    while (url.length < totalLength) {
        if (percentAt !== undefined && url.length === percentAt && totalLength - url.length >= 3) {
            url += "%20";
            continue;
        }
        if (percentAt !== undefined && url.length > percentAt - 3 && url.length < percentAt)
            url += "a";
        else
            url += "abcdefghij".charAt(url.length % 10);
    }
    return url.substring(0, totalLength);
}

// A frame looks like fn@url:line:column. Pull out the url.
function sourceURLOfDataFrame(stack)
{
    const frame = stack.split("\n").filter(function (each) { return each.indexOf("data:text/javascript,") !== -1; })[0];
    if (!frame)
        return null;
    return frame.substring(frame.indexOf("data:text/javascript,")).replace(/:\d+:\d+$/, "");
}

async function urlLengthInStackFor(totalLength, percentAt)
{
    const module = await import(makeModuleURL(totalLength, percentAt));
    const url = sourceURLOfDataFrame(module.mk().stack);
    return url === null ? -1 : url.length;
}

// This file's own URL is not a data: URL, so it should stay whole.
// Read it here: inside the async function below there is no caller frame.
window.ordinaryFrameSurvives = new Error().stack.indexOf("error-stack-data-url-truncation.html") !== -1;

async function runTests()
{
    try {
        // Long data: URL, cut to 1024.
        window.plainLength = await urlLengthInStackFor(5000);
        shouldBe("plainLength", "1024");

        // %20 starts at 1023, so cut before it.
        window.escapeAtEndLength = await urlLengthInStackFor(5000, limit - 1);
        shouldBe("escapeAtEndLength", "1023");

        // %20 starts at 1022, so cut before it.
        window.escapeStraddlingLength = await urlLengthInStackFor(5000, limit - 2);
        shouldBe("escapeStraddlingLength", "1022");

        // Under 1024, so unchanged.
        window.shortLength = await urlLengthInStackFor(500);
        shouldBe("shortLength", "500");

        // Not a data: URL, so unchanged.
        shouldBeTrue("ordinaryFrameSurvives");
    } catch (exception) {
        testFailed("threw " + exception);
    }
    finishJSTest();
}

runTests();
</script>
</body>
</html>