API changes for v3

[Morganamilo]

• Some getters should return Option Tracking for functions that should return Option #19
• FileList::contains has unneeded Result<>
• Alpm should not be Send
• Rename CommitResult::FileConflict -> CommitResult::Fileconflicts
• Rework Commit/Prepare Result to be lazy?
• Add error and Commit/Prepare Result should be more consistent with eachother
• Package::files() should be an option. No it's fine as is. Actually no
• Remove handle needed to make an alpmlistmut and remove lifetimes.
• &mut self for string setters

[Morganamilo]

trans prepare (and commit) currently look like this:

pub fn trans_prepare(&mut self) -> Result<(), (PrepareResult<'_>, Error)>

With PrepareResult being:

pub enum PrepareResult<'a> {
    PkgInvalidArch(AlpmListMut<'a, Package<'a>>),
    UnsatisfiedDeps(AlpmListMut<'a, DependMissing>),
    ConflictingDeps(AlpmListMut<'a, OwnedConflict>),
    Ok,
}

This can be a bit awkward as you can't just handle.trans_prepare()? as PrepareResult doesn't implement Error or Display. It's also hard to pass with anyhow as due to storing the alpm lists the value is !Send and !Sync. It makes it a little awkward as you have to .map_err(|e| e.1) and you also lose some of the information.

Also PrepareResult should be named PrepareError.

It should probably be more like trans_add_pkg() which returns Result<(), AddError> . Store the error and the value and implement std Error and into alpm::Error. The function should also just hold a raw alpmlist and have a getter to turn it the error value.

[Morganamilo]

I'm considering inverting how the structs work for v3.

instead of a Pkg struct that contains a pointer it will be &Pkg that contains an alpm_pkg_t. Then like &str, &Pkg will only be holdable by reference. I think that may work better for some ergonomics.

[Morganamilo]

Unions can be done in a way that doesn't require us to match on them: https://github.com/rust-lang/rfcs/blob/master/text/2195-really-tagged-unions.md

[Morganamilo]

I got around to implementing all of this in https://github.com/archlinux/alpm.rs/tree/v3.

Only think not done is transmuting the unions to enums directly. As due to padding that would require putting all the fields in the enum variant directly and not a struct. Which then causes issues as I wish to keep them private.

Don't expect this any time soon as I don't see a new pacman any time soon and it also depend on an un merged patch.