0.9 changes prevent to use a std::fs::File directly with to_writer and to_writer_pretty

[Ummon]

As to_writer and to_writer_pretty need a std::fmt::Write as writer it's not possible to give them a std::fs::File directly.

It was possible in 0.8 to do that:

let file = File::create("file.ron").unwrap();
to_writer(file, &my_ron);

But it's not possible anymore.

Is there an easy way to write directly to a file? If yes it should be great to have an example in /examples/ as the reader example /examples/decode_file.rs.

[juntyr]

Thank you for raising this issue with the updated API. The decision to move to fmt::Writer was taken because it provides stricter guarantees to users of RON, but I missed your case where you don’t need those guarantees.

At the moment there is no direct way to serialise to io::Write. Whatever we do next, there is the https://crates.io/crates/io-adapters crate that implements this conversion.

We could add additional methods that take io::Write (e.g. to_io_writer) and use an adapter internally. Would that work for you?

[juntyr]

I’m thinking that one fun way to write the adapter internally would be to create a Display impl that fmt::Write’s to the fmt::Formatter and to then pass that Display impl into io::Write::write_fmt