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https://github.com/clap-rs/clap
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647896d929
This is the derive support for #3774 (see also #3775, #3777) This combined with `value_parser` replaces `parser`. The main frustration with this is that `ArgAction::Count` (the replacement for `parse(from_occurrences)` must be a `u64`. We could come up with a magic attribute that is meant to be the value parser's parsed type. We could then use `TryFrom` to convert the parsed type to the user's type to allow more. That is an exercise for the future. Alternatively, we have #3792. Prep for this included - #3782 - #3783 - #3786 - #3789 - #3793
32 lines
888 B
Rust
32 lines
888 B
Rust
use clap::Parser;
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#[derive(Parser, Debug, PartialEq)]
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#[clap(author, version, about, long_about = None)]
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struct Opt {
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// Default parser for `Set` is FromStr::from_str.
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// `impl FromStr for bool` parses `true` or `false` so this
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// works as expected.
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#[clap(long, action = clap::ArgAction::Set)]
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foo: bool,
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// Of course, this could be done with an explicit parser function.
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#[clap(long, action = clap::ArgAction::Set, value_parser = true_or_false, default_value_t)]
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bar: bool,
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// `bool` can be positional only with explicit `action` annotation
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#[clap(action = clap::ArgAction::Set)]
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boom: bool,
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}
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fn true_or_false(s: &str) -> Result<bool, &'static str> {
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match s {
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"true" => Ok(true),
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"false" => Ok(false),
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_ => Err("expected `true` or `false`"),
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}
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}
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fn main() {
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let opt = Opt::parse();
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dbg!(opt);
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}
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