This adds a new `Cargo.toml` feature named `deprecated` that opts
controls whether deprecation warnings show up. This is starting off as
non-default though that may change (see below).
Benefits
- Allows a staged rollout so a smaller subset of users see new
deprecations and can report their experience with them before everyone
sees them. For example, this reduces the number of people who have to
deal with #3822.
- This allows people to defer responding to each new batch of
deprecations and instead do it at once. This means we should
reconsider #3616.
The one risk is people who don't follow blog posts and guides having a
harder time upgrading to the next breaking release without the warnings
on by default. For these users, we reserve the right to make the
`deprecated` feature `default`. This is most likely to happen in a
minor release that is released in conjunction with the next major
release (e.g. when releasing 4.0.0, we release a 3.3.0 that enables
deprecations by default). By using a feature, users can still disable
this if they want.
Thanks @joshtriplett for the idea
Though this is changing an API item we export, we do not consider this a
breaking change because
- This was an implementation detail of the macros and people shouldn't be using it directly
- The `macro_rules` macro is coupled to `clap` because they are in the
same crate
- The derive macro is coupled to `clap` because `clap` declares a
`=x.y.z` dependency on `clap_derive
Fixes#3828
This is mostly about avoiding criterion's build times when just
developing clap itself.
I'm assuming the derive test changed because criterion's clap v2 isn't
in the dependency tree anymore.
`multicall` allows you to have one binary expose itself as multiple
programs, like busybox does. This also works well for user clap for
parsing REPLs.
Fixes#2861
While `clap` depends on `clap_derive`, `clap_derive` inherently has a
dependency on `clap` because it generates code assuming at least a
specific clap version. If a new `clap_derive` is used with an old
`clap`, it'll generate code that won't compile.
We've kept things loose because of
- Bad experiences with overly constrained version reqs
- To not force new `clap` versions to release `clap_derive`.
- People should have a lock file anyways
The downsides:
- `cargo install` does not use `Cargo.lock` by default, required
`--locked`
- If we want people to not skip non-patch releases when upgrading, we
need it to not be a pain
