Module actions 

Flag Actions

Like Clap, a flag’s behaviour can be chosen with action. Only this subset of Clap’s ArgAction is supported, written as a bare name or as ArgAction::Name:

Action	Field type	Absent	Each occurrence
SetTrue	bool	false	sets true (the default for bool)
SetFalse	bool	true	sets false
Count	integer (u8, u32, i64, usize, …)	0	adds one, saturating at the type’s maximum

Count counts every occurrence, including repeated short flags grouped in one argument (-vvv) and mixed short and long forms (-vv --verbose). A default (default_value_t = ...) replaces the value used when the flag is absent; as in Clap, it is not a starting point for counting. Flags never take a value, so --verbose=2 is rejected as an unknown option.

use getargs_derive::GetArgs;

#[derive(GetArgs)]
struct Cli {
    /// More output, repeat for even more.
    #[arg(short, long, action = Count)]
    verbose: u8,
    /// Disable colored output.
    #[arg(long = "no-color", action = SetFalse)]
    color: bool,
}

let cli = Cli::from_args(["-vvv", "--verbose", "--no-color"].into_iter())?;
assert_eq!(cli.verbose, 4);
assert!(!cli.color);

let cli = Cli::from_args([].into_iter())?;
assert_eq!(cli.verbose, 0);
assert!(cli.color);

In the generated help, a Count flag is followed by ... (-v, --verbose...), as in Clap. See Generated Help.

Compile-Time Diagnostics

The macro reports a compile error, pointing at the offending attribute or field, for:

• unsupported action values, and action without a value;
• action without short/long;
• SetTrue/SetFalse on a non-bool field, and Count on a non-integer field;
• value_name on a field with an action.