The remove functions no longer return `Arc` but the core type, at the
cost of requiring `Clone`. I originally held off on this
in #3732 in the hope of gracefully transition the derive and requiring
`Clone` would have been a breaking change but when it came to #3734, I didn't
find a way to make it work without a breaking change, so I made it
opt-in. This means I can force the `Clone` requirement now.
I added the requirement for `Clone` everywhere else in the hopes that in
the future, we can drop the `Arc` without a breaking change.
When to show usage? We are currently mixed about it. For `validator`,
we didn't show it at all. Sometimes we show the used arguments and
sometimes we don't.
With `ValueParser`, I ran into the problem that we weren't showing the
used arguments like we had previously in some cases. In deciding how to
solve this, I went with the simplest route for now and removed it as the
usage likely doesn't add much context to help people solve their
problem, more so the recommendation for help. We'll see how the
feedback is on this and adjust.
To set the type, we offer
- `ValueParser::<type>` short cuts for natively supported types
- `TypedValueParser` for fn pointers and custom implementations
- `value_parser!(T)` for specialized lookup of an implementation
(inspired by #2298)
The main motivation for `value_parser!` is to help with `clap_derive`s
implementation but it can also be convinient for end-users.
When reading, this replaces nearly all of our current `ArgMatches` getters with:
- `get_one`: like `value_of_t`
- `get_many`: like `values_of_t`
It also adds a `get_raw` that allows accessing the `OsStr`s without
panicing.
The naming is to invoke the idea of a more general container which I
want to move this to.
The return type is a bit complicated so that
- Users choose whether to panic on invalid types so they can do their
own querying, like `get_raw`
- Users can choose how to handle not present easily (#2505)
We had to defer setting the `value_parser` on external subcommands,
for consistency sake, because `Command` requires `PartialEq` and
`ValueParser` does not impl that trait. It'll have to wait until a
breaking change.
Fixes#2505
Unfortunately, we can't track using a `ValueParser` inside of `Command`
because its `PartialEq`. We'll have to wait until a breaking change to
relax that.
Compatibility:
- We now assert on using the wrong method to look up defaults. This
shouldn't be a breaking change as it'll assert when getting a real
value.
- `values_of`, et al delay panicing on the wrong lookup until the
iterator is being processed.
The top-level API for clap is getting a bit bloated. By exposing these
modules, we'll be able to continue to add new, less commonly used types
while keeping the main API focused.
