This was ported over from the usage parser which modeled after docopt.
We just never got around to implementing the rest of the syntax.
However, when considering this as a standalone feature, an
`arg!(--flag <value>)`, outside of other context, should be optional.
This is how the help would display it.
Fixes#4206
The main breakinge change cases:
- `&[char]`: now requires removing `&`
- All other non-ID `&[_]`: hopefully #1041 will make these non-breaking
Fixes#2870
This reduces ambiguity in how the different "multiple" parts of the API
interact and lowrs the amount of API surface area users have to dig
through to use clap.
For now, this is only a matter of cleaning up the public API. Cleaning
up the implementation is the next step.
With `number_of_values` being per-occurrence now, its doesn't make sense
for `number_of_values(0)` to set `takes_value(true)` or for
`number_of_values(1)` to set `multiple_values(true)`.
In addition, an assert is made if the user works around this
This mostly exist for
- Knowing of the value came from the command-line but we now have
`ArgMatches::source`
- Counting the number of flags but we now have `ArgAction::Count`
`-h` (short help) still shows the same.
This gates it behind an `unstable-v4` feature flag to avoid disrupting users who set the help without knowing where all it shows up (particularly derive users where `ArgEnum` is automatically extracting the help).
Fixes#3312
When an Arg uses .min_values(0), that arg's value(s) are effectively
optional. This is conventionaly denoted in help messages by wrapping the
arg's values in square brackets. For example:
--foo[=value]
--bar [value]
This kind of argument can be seen in the wild in many git commands; e.g.
git-status(1).
Signed-off-by: Peter Grayson <pete@jpgrayson.net>
This is prep for moving the derive tests. Besides organizing the test
folder for each API, this should reduce link time at the cost of
re-compiling more when a test changes.
