Mailbox does not implement `TryInto<Mailbox>`

[felinira]

Many Client methods expect a impl TryInto<Mailbox<'_>, Error = ValidationError>, but Mailbox does not actually implement this trait (only infallibly through the blanket From<T> for T implementation in Rust std). Not sure whether to report it at imap-types or here, but this makes it a little difficult to pass an already existing mailbox type :) And I don't think you can implement TryFrom twice, as Error is an associated type, so either way it probably needs to be solved here. Maybe through some new trait that allows both Into and TryInto, or by delegating the responsibility of conversion to the caller.

[soywod]

Yes indeed, we will not be able to implement TryFrom for itself. I often face this dilemna and I'm not sure which solution is the best between converting inside or outside. Both have pros and cons. Any advice?

[felinira]

I would recommend to only auto convert via Into. If it's not possible to use Into, take the types directly.

The Mailbox example has one other caveat: One would expect that the TryInto implementation from str does implicit mUTF-7 conversion. str is UTF-8. However, it does not. This caused a server error for me before I did that conversion myself before.

[duesee]

Hm... yeah... I decided against handling mUTF-7 on the imap-types level because I was afraid to confine ourselfes too much. See duesee/imap-codec#370.

A Mailbox is (simplified ) an AString which means an Atom or a String (which means a Quoted or a Literal). What this says to me is: A Mailbox is a bunch of bytes (w/o 0x00).

imap-types will try all variants from atom, quoted, literal, error (due to 0x00) and send the mailbox in the most simple variant that is possible.

@felinira, can you open an issue in the imap-codec repo and provide more details? We stumbled upon mUTF-7 already but so far I was afraid to tackle it and just implemented the RFC in it's most generic form. But: This should never had lead to a server error. This is what I want to promise with imap-types :-)

[duesee]

By the way: If you feel something could be off with a client/server, let's discuss via an issue in https://github.com/modern-email/defects.