SetQueryParam strips leading slash in file URI with empty hostname

[markmccaigue]

Hi,

I have written the below test to illustrate what I suspect is a problem with the handling of slashes with file URIs.

[Test]
public void FlurlUrl_PreservesLeadingSlash()
{
    var urlString = "file:///document";

    var flurl = new Url(urlString);

    Assert.AreEqual(urlString, flurl.ToString());

    var queryKey = "queryKey";
    var queryValue = "queryValue";
    flurl = flurl.SetQueryParam(queryKey, queryValue);

    Assert.AreEqual($"{urlString}?{queryKey}={queryValue}", flurl.ToString());
}

I would expect this test to pass, but instead it fails with the following message:

String lengths are both 36. Strings differ at index 7.
Expected: "file:///document?queryKey=queryValue"
But was:  "file://document/?queryKey=queryValue"

In summary, I believe Flurl is removing that third slash and inadvertently generating an invalid URI.

Many thanks for your help.

[tmenier]

Interesting. I'll be honest, I didn't know the triple-slash notation was a thing when I wrote the normalization logic. But it looks legitimate and I'll make sure it's not tampered with when specified.

In summary, I believe Flurl is removing that third slash and inadvertently generating an invalid URI.

Technically not correct to say it's an invalid URI, but it's certainly the URI you expected, so point taken. 😉

[tmenier]

note to self: https://superuser.com/a/352134

[markmccaigue]

Interesting. I'll be honest, I didn't know the triple-slash notation was a thing when I wrote the normalization logic. But it looks legitimate and I'll make sure it's not tampered with when specified.

In summary, I believe Flurl is removing that third slash and inadvertently generating an invalid URI.

Technically not correct to say it's an invalid URI, but it's certainly the URI you expected, so point taken. 😉

Haha fair enough 😁 Thanks a million!

[EamonHetherton]

Just reporting that I am experiencing this issue too.

It's actually worse than the issue suggests as it will mutate the URL and remove the extra slash just by checking if a query param exists, even if you do not intend to mutate the URL in any way.

[Fact]
public void FlurlUrl_PreservesLeadingSlash()
{
    var urlString = "file:///document";

    var flurl = new Url(urlString);

    Assert.Equal(urlString, flurl.ToString());

    var queryKey = "queryKey";
    flurl.QueryParams.Contains(queryKey);

    Assert.Equal(urlString, flurl.ToString());
}

As a result, I was seeing a reload loop in my code. Using chromium (via CefSharp) would add the third slash and generate an "OnAddressChanged" event, then my logic to ensure a query parameter existed would remove the third slash as a result of this issue even when the Url was otherwise correct triggering a new page load as the URL was now "different":
-> load "file://" url
-> chromium adds slash
-> OnAddressChanged
-> flurl removes slash by checking for query param
-> load "file://" url
-> ad infinitum.

For now, I will workaround in the client code by adding the extra '/' back to a "file" scheme URL if it was there to start with but may attempt to fix it with a pull request if I get time.