Re-enable trust-dns feature

[seanmonstar]

The trust-dns feature was disabled in #617 as the dependency was not yet updated to std::future. We should re-enable once it is available.

[daxpedda]

This was fixed here: hickory-dns/hickory-dns#849.

EDIT: So basically from version 0.18.0-alpha.1.

[seanmonstar]

We can re-enable once the version is out of alpha!

[seanmonstar]

Some notes as I tried to re-enable this:

• ResolveError implements Fail instead of std::error::Error. I can get around this since it also implements Into<io::Error>, but it'd be better to not include failure in the dependency tree.
• AsyncResolver requires passing a tokio::runtime::Handle to its constructors, but we don't have one and have no way of materializing one.

[daxpedda]

• ResolveError implements Fail instead of std::error::Error. I can get around this since it also implements Into<io::Error>, but it'd be better to not include failure in the dependency tree.

It still implements Display, wihch is what we are using as far as I can see:

reqwest/src/dns.rs

Line 73 in 35c6ddd

.map_err(|err| io::Error::new(io::ErrorKind::Other, err.to_string()))

In any case, trust-dns pulls in failure anyway, so no loss there.

• AsyncResolver requires passing a tokio::runtime::Handle to its constructors, but we don't have one and have no way of materializing one.

See hickory-dns/hickory-dns#977 and tokio-rs/tokio#2040.

I would like to take a stab at this when the Handle is resolved, if thats alright.

[bluejekyll]

@seanmonstar, we can remove all depdencies on Fail and failure. We'll lose backtrace, but that is coming in std.

might need a 0.19 release of trust-dns...

[bluejekyll]

FYI: hickory-dns/hickory-dns#988

This drops failure, uses thiserror for some std error generation. Is there anything else? I’m planning to do a 0.19 release this weekend to get this out.

[bluejekyll]

Ok, 0.19 is released.