cannot use pattern syntax inside ipv6 address

[wanderview]

We added support to the constructor string parser over in #113. This allows ipv6 literals like new URLPattern("http://[\\:\\:1]") to be used. There is, however, a separate ipv6 problem.

If you have an ipv6 hostname it becomes impossible to use any pattern syntax inside the address. For example, all of these currently throw:

// these throw right now
new URLPattern({ hostname: '[:address]' });
new URLPattern("http://[:address]");

The problem is that we pass only the "plain text" parts of the pattern to the hostname encoding callback. The callback then delegates to the URL parsing state machine. So the URL parsing state machine sees a [ string by itself. This throws since the URL parsing state machine requires any hostname starting with [ to also end with a ] and then also successfully parse as ipv6.

We will need to use a more lenient hostname encoding callback for hostname patterns that appear to be ipv6.