Trait TypedValueParser

pub trait TypedValueParser:
    Clone
    + Send
    + Sync
    + 'static {
    type Value: Send + Sync + Clone;

    // Required method
    fn parse_ref(
        &self,
        cmd: &Command,
        arg: Option<&Arg>,
        value: &OsStr,
    ) -> Result<Self::Value, Error>;

    // Provided methods
    fn parse_ref_(
        &self,
        cmd: &Command,
        arg: Option<&Arg>,
        value: &OsStr,
        _source: ValueSource,
    ) -> Result<Self::Value, Error> { ... }
    fn parse(
        &self,
        cmd: &Command,
        arg: Option<&Arg>,
        value: OsString,
    ) -> Result<Self::Value, Error> { ... }
    fn parse_(
        &self,
        cmd: &Command,
        arg: Option<&Arg>,
        value: OsString,
        _source: ValueSource,
    ) -> Result<Self::Value, Error> { ... }
    fn possible_values(
        &self,
    ) -> Option<Box<dyn Iterator<Item = PossibleValue> + '_>> { ... }
    fn map<T, F>(self, func: F) -> MapValueParser<Self, F>
       where T: Send + Sync + Clone,
             F: Fn(Self::Value) -> T + Clone { ... }
    fn try_map<T, E, F>(self, func: F) -> TryMapValueParser<Self, F>
       where F: Fn(Self::Value) -> Result<T, E> + Clone + Send + Sync + 'static,
             T: Send + Sync + Clone,
             E: Into<Box<dyn Error + Send + Sync + 'static>> { ... }
}

Parse/validate argument values

As alternatives to implementing TypedValueParser,

• Use Fn(&str) -> Result<T, E> which implements TypedValueParser
• TypedValueParser::map or TypedValueParser::try_map to adapt an existing TypedValueParser

See ValueParserFactory to register TypedValueParser::Value with value_parser!.

Example

#[derive(Clone)]
struct Custom(u32);

#[derive(Clone)]
struct CustomValueParser;

impl clap::builder::TypedValueParser for CustomValueParser {
    type Value = Custom;

    fn parse_ref(
        &self,
        cmd: &clap::Command,
        arg: Option<&clap::Arg>,
        value: &std::ffi::OsStr,
    ) -> Result<Self::Value, clap::Error> {
        let inner = clap::value_parser!(u32);
        let val = inner.parse_ref(cmd, arg, value)?;

        const INVALID_VALUE: u32 = 10;
        if val == INVALID_VALUE {
            let mut err = clap::Error::new(ErrorKind::ValueValidation)
                .with_cmd(cmd);
            if let Some(arg) = arg {
                err.insert(ContextKind::InvalidArg, ContextValue::String(arg.to_string()));
            }
            err.insert(ContextKind::InvalidValue, ContextValue::String(INVALID_VALUE.to_string()));
            return Err(err);
        }

        Ok(Custom(val))
    }
}

Required Associated Types

type Value: Send + Sync + Clone

Argument’s value type

Required Methods

fn parse_ref( &self, cmd: &Command, arg: Option<&Arg>, value: &OsStr, ) -> Result<Self::Value, Error>

Parse the argument value

When arg is None, an external subcommand value is being parsed.

Provided Methods

fn parse_ref_( &self, cmd: &Command, arg: Option<&Arg>, value: &OsStr, _source: ValueSource, ) -> Result<Self::Value, Error>

Parse the argument value

When arg is None, an external subcommand value is being parsed.

fn parse( &self, cmd: &Command, arg: Option<&Arg>, value: OsString, ) -> Result<Self::Value, Error>

Parse the argument value

When arg is None, an external subcommand value is being parsed.

fn parse_( &self, cmd: &Command, arg: Option<&Arg>, value: OsString, _source: ValueSource, ) -> Result<Self::Value, Error>

Parse the argument value

When arg is None, an external subcommand value is being parsed.

fn possible_values( &self, ) -> Option<Box<dyn Iterator<Item = PossibleValue> + '_>>

Reflect on enumerated value properties

Error checking should not be done with this; it is mostly targeted at user-facing applications like errors and completion.

fn map<T, F>(self, func: F) -> MapValueParser<Self, F>

where T: Send + Sync + Clone, F: Fn(Self::Value) -> T + Clone,

Adapt a TypedValueParser from one value to another

Example

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::SetTrue)
            .value_parser(
                BoolishValueParser::new()
                .map(|b| -> usize {
                    if b { 10 } else { 5 }
                })
            )
    );

let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_one::<usize>("flag").copied(),
    Some(10)
);

let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_one::<usize>("flag").copied(),
    Some(5)
);

fn try_map<T, E, F>(self, func: F) -> TryMapValueParser<Self, F>

where F: Fn(Self::Value) -> Result<T, E> + Clone + Send + Sync + 'static, T: Send + Sync + Clone, E: Into<Box<dyn Error + Send + Sync + 'static>>,

Adapt a TypedValueParser from one value to another

Example

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .value_parser(
                OsStringValueParser::new()
                .try_map(verify_ext)
            )
    );

fn verify_ext(os: OsString) -> Result<PathBuf, &'static str> {
    let path = PathBuf::from(os);
    if path.extension() != Some(OsStr::new("rs")) {
        return Err("only Rust files are supported");
    }
    Ok(path)
}

let error = cmd.clone().try_get_matches_from(["mycmd", "--flag", "foo.txt"]).unwrap_err();
error.print();

let matches = cmd.try_get_matches_from(["mycmd", "--flag", "foo.rs"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_one::<PathBuf>("flag").map(|s| s.as_path()),
    Some(Path::new("foo.rs"))
);

Object Safety

This trait is not object safe.

Implementors

impl TypedValueParser for BoolValueParser

type Value = bool

impl TypedValueParser for BoolishValueParser

type Value = bool

impl TypedValueParser for FalseyValueParser

type Value = bool

impl TypedValueParser for NonEmptyStringValueParser

type Value = String

impl TypedValueParser for OsStringValueParser

type Value = OsString

impl TypedValueParser for PathBufValueParser

type Value = PathBuf

impl TypedValueParser for PossibleValuesParser

type Value = String

impl TypedValueParser for StringValueParser

type Value = String

impl TypedValueParser for UnknownArgumentValueParser

type Value = String

impl<E: ValueEnum + Clone + Send + Sync + 'static> TypedValueParser for EnumValueParser<E>

type Value = E

impl<F, T, E> TypedValueParser for F

where F: Fn(&str) -> Result<T, E> + Clone + Send + Sync + 'static, E: Into<Box<dyn Error + Send + Sync + 'static>>, T: Send + Sync + Clone,

type Value = T

impl<P, F, T> TypedValueParser for MapValueParser<P, F>

where P: TypedValueParser, P::Value: Send + Sync + Clone, F: Fn(P::Value) -> T + Clone + Send + Sync + 'static, T: Send + Sync + Clone,

type Value = T

impl<P, F, T, E> TypedValueParser for TryMapValueParser<P, F>

where P: TypedValueParser, P::Value: Send + Sync + Clone, F: Fn(P::Value) -> Result<T, E> + Clone + Send + Sync + 'static, T: Send + Sync + Clone, E: Into<Box<dyn Error + Send + Sync + 'static>>,

type Value = T

impl<T: TryFrom<i64> + Clone + Send + Sync + 'static> TypedValueParser for RangedI64ValueParser<T>

where <T as TryFrom<i64>>::Error: Send + Sync + 'static + Error + ToString,

type Value = T

impl<T: TryFrom<u64> + Clone + Send + Sync + 'static> TypedValueParser for RangedU64ValueParser<T>

where <T as TryFrom<u64>>::Error: Send + Sync + 'static + Error + ToString,

type Value = T