While having convinience derives can be helpful, deriving traits that
are not used in similar situations (`Clap` and `ArgEnum`) can make
things harder
- From a user, derives are opaque and create uncertainty on how to use
the API if not kept crystal clear (deriving a name gives you the trait
by that name)
- This makes documentation harder to write and read
- You can use types in unintended places, which is made worse for crate
APIs because changing this breaks compatibility.
Fixes#2584
- help / version flag report correct application name when generated
with clap_derive and an Enum.
- add clap_derive unit tests for application name:
file: clap_derive/tests/app_name.rs
tests: app_name_in_[short|long]_[help|version]_from_[struct|enum]()
In the `Clap` derive macro, a function parameter named `arg_matches` is
generated using `quote!` - as a result, this parameter ends up with
call-site hygiene. However, `arg_matches` is written literally within
several `quote_spanned!` blocks, which generate an `arg_matches` token
with the hygiene of whatever span was passed to `quote_spanned!`.
If these two hygienes are different (for example, if the user invokes
the derive macro from a `macro_rules!` macro), then a usage of
`arg_matches` may not resolve to the `arg_matches` parameter definition.
This commit changes the generation of `arg_matches` identifiers to
always use `quote!`, ensuring that they will always be considered the
'same' identifier by Rust.
Due to macro expansions, a `syn` type may be wrapped in multiple
'layers' of `syn::Type::Group`. However, `clap_derive` currently does
not check for `syn::Type::Group`, which will cause an `Option` (along
with other matched types) to fail to be detected when it results from a
macro expansion.
This commit 'unwraps' outer type groups before checking the
user-provided types against well-known types. Currently, these groups
may not be present due to a rustc bug (rust-lang/rust#43081)
However, once https://github.com/rust-lang/rust/pull/73084 is merged,
these groups will be present in more cases. This commit makes `clap`
compatible with both older and newer versions of rustc.
This PR switches the Arg::Short macro to take a character instead of a string. It removes the hacky code in the Method to_token method and implements the logic for Short when parsing the clap derive arguments.
Fixes#1815.
