Instead they should behave like `default_value`/`default_values`.
In implementingt this, I didn't see any reason to be using a `VecMap`.
In fact, this helped simplify the code / make intent clearer.
With this, we are also able to simplify the derive macro work from #2633.
Fixes#2634
BREAKING CHANGE: `value_name`/`value_names` always overwrite, rather
than append. We expect the impact to be minimal.
Right now
- `default_value="something"` is a raw method
- `default_value` uses native types
This commit splits the meanings
- `default_value="something"` is a raw method
- `default_value_t` uses `T::default()`
- `default_value_t=expr` uses an expression that evaluates to `T`
This is meant to mirror the `value_of` / `value_of_t` API.
At the moment, this is limited to `T: Display` to work with clap's
default system. Something we can look at in the future is a way to
loosen that restriction. One quick win is to specialize when `arg_enum`
is set. The main downside is complicating the processing of attributes
because it then means we need some processed before others.
Since this builds on `clap`s existing default system, this also means
users do not get any performance gains out of using `default_value_t`,
since we still need to parse it but we also need to convert it to a
string.
Fixes#1694
It looks like CI hasn't been running on this and we've introduced some
problems. It looks like we had an off-by-one error in the check for
MSRV for deciding to run ui tests.
It turns out `value_name` appends, so by setting an implicit and
explicit `value_name`, the user gets both and `num_vals=2`.
There is still a question on `value_name` and whether its documentation
or behavior needs updating. If that changes, then this can be
simplified by reverting back.
Fixes#2632
When using `#[clap(flatten)]` inside of a `Subcommand`, we would do a
`from` instead of an `update`.
The challenge is knowing when we are
going into a flattened subcommand vs changing the variant. To resolve
this, I added a `Subcommand:has_subcommand(name)` trait method that we
generate, so we can ask.
I debated putting this fix inside of the Builder API but I figure this
makes it so you "pay for what you use", with the derive API giving it to
you "for free".
A potential next step is to improve the default value name. I tend to
use value_name to hint at how to use an argument, which correlates with
types. We could add a
`ValueName::value_name(fallback: &str) -> &str` with impls for common
types, so we get more of a usage-based result.
Fixes#2608
One of the challenges with #2255 is for the user to discover whats going
wrong. This helps by at least telling people how they got into a bad
state and we can search for the code within the derive.
Before, when doing an `update` involving subcommands, we generated
parsing rules for the `from` case instead, requiring all arguments to be
present.
This switches us to descending into `update` code and adds tests to
verify it works.
This is a part of #2605
When debugging #2586, I noticed we were developing match cases for
variant names that were flattened. At minimum, this is dead code and at
worst this could cause the wrong behavior if a user does an update with
one of those names.
Depends on #2587Fixes#2588
`structopt` originally allowed
```
pub enum Opt {
Daemon(DaemonCommand),
}
pub enum DaemonCommand {
Start,
Stop,
}
```
This was partially broken in #1681 where `$ cmd daemon start` works but `cmd daemon`,
panics. Originally, `structopt` relied on exposing the implementation
details of a derived type by providing a `is_subcommand` option, so we'd
know whether to provide `SubcommandRequiredElseHelp` or not. This was
removed in #1681Fixes#2005
Before, partial command lines would panic at runtime. Now it'll be a
compile error
For example:
```
pub enum Opt {
Daemon(DaemonCommand),
}
pub enum DaemonCommand {
Start,
Stop,
}
```
Gives:
```
error[E0277]: the trait bound `DaemonCommand: clap::Args` is not satisfied
--> clap_derive/tests/subcommands.rs:297:16
|
297 | Daemon(DaemonCommand),
| ^^^^^^^^^^^^^ the trait `clap::Args` is not implemented for `DaemonCommand`
|
= note: required by `augment_args`
```
To nest this, you currently need `enum -> struct -> enum`. A later
change will make it so you can use the `subcommand` attribute within
enums to cover this case.
This is a part of #2005
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
