Inconsistent parsing of magnet xt param

[angrynode]

See also the tests submitted in #1083

Maybe this is out-of-scope for the url crate as magnet links are URIs but not URLs. If so, feel free to close and add a mention in the README that non-location URIs are unsupported.

In the case of magnets, BEP-0009 doesn't specify the encoding. However, the examples used do not percent-encode the xt delimiters so they should probably not be encoded at all. According to my limited testing, qBittorrent supports url-encoded xt params, but not Transmission, which confirms my intuition.

However, magnet URIs also contains actual URLs for trackers (tr params) which should 100% be url-encoded, including the : in there.

[valenting]

I assume you're referring to this example in #1083

use url::{Url};

fn main() {
    let mut url = Url::parse("magnet:").unwrap();
    {
        let mut query_pairs = url.query_pairs_mut();
        query_pairs.append_pair("xt", "urn:btmh:foo");
    }
    assert_eq!(url.as_str(), "magnet:?xt=urn:btmh:foo");
}

In this case actually the URL can be parsed correctly

use url::{Url};

fn main() {
    let url1 = Url::parse("magnet:?xt=urn:btmh:foo").unwrap();
    println!("{:?}", url1.as_str());
}

The problem is that query_pairs_mut appends with append_pair which is part of the form_urlencoded, which is probably not what we want for magnet URIs.

[angrynode]

The problem is that query_pairs_mut appends with append_pair which is part of the form_urlencoded, which is probably not what we want for magnet URIs.

Exactly! I'm not sure what's the correct approach. Maybe Serializer could have append_pair and append_pair_unencoded if that's possible?