Struct Error

pub struct Error<F = RichFormatter>
where
    F: ErrorFormatter,
{ /* private fields */ }

Command Line Argument Parser Error

See Command::error to create an error.

Implementations

impl<F> Error<F>

where F: ErrorFormatter,

pub fn raw(kind: ErrorKind, message: impl Display) -> Error<F>

Create an unformatted error

This is for you need to pass the error up to a place that has access to the Command at which point you can call Error::format.

Prefer Command::error for generating errors.

pub fn format(self, cmd: &mut Command) -> Error<F>

Format the existing message with the Command’s context

pub fn new(kind: ErrorKind) -> Error<F>

Create an error with a pre-defined message

See also

• Error::insert
• Error::with_cmd

Example

let cmd = clap::Command::new("prog");

let mut err = clap::Error::new(ErrorKind::ValueValidation)
    .with_cmd(&cmd);
err.insert(ContextKind::InvalidArg, ContextValue::String("--foo".to_owned()));
err.insert(ContextKind::InvalidValue, ContextValue::String("bar".to_owned()));

err.print();

pub fn with_cmd(self, cmd: &Command) -> Error<F>

Apply Command’s formatting to the error

Generally, this is used with Error::new

pub fn apply<EF>(self) -> Error<EF>

where EF: ErrorFormatter,

Apply an alternative formatter to the error

Example

let cmd = Command::new("foo")
    .arg(Arg::new("input").required(true));
let matches = cmd
    .try_get_matches_from(["foo", "input.txt"])
    .map_err(|e| e.apply::<KindFormatter>())
    .unwrap_or_else(|e| e.exit());

pub fn kind(&self) -> ErrorKind

Type of error for programmatic processing

pub fn context(&self) -> impl Iterator<Item = (ContextKind, &ContextValue)>

Additional information to further qualify the error

pub fn get(&self, kind: ContextKind) -> Option<&ContextValue>

Lookup a piece of context

pub fn insert( &mut self, kind: ContextKind, value: ContextValue, ) -> Option<ContextValue>

Insert a piece of context

pub fn use_stderr(&self) -> bool

Should the message be written to stdout or not?

pub fn exit_code(&self) -> i32

Returns the exit code that .exit will exit the process with.

When the error’s kind would print to stderr this returns 2, else it returns 0.

pub fn exit(&self) -> !

Prints the error and exits.

Depending on the error kind, this either prints to stderr and exits with a status of 2 or prints to stdout and exits with a status of 0.

pub fn print(&self) -> Result<(), Error>

Prints formatted and colored error to stdout or stderr according to its error kind

Example

use clap::Command;

match Command::new("Command").try_get_matches() {
    Ok(matches) => {
        // do_something
    },
    Err(err) => {
        err.print().expect("Error writing Error");
        // do_something
    },
};

pub fn render(&self) -> StyledStr

Render the error message to a StyledStr.

Example

use clap::Command;

match Command::new("Command").try_get_matches() {
    Ok(matches) => {
        // do_something
    },
    Err(err) => {
        let err = err.render();
        println!("{err}");
        // do_something
    },
};

Trait Implementations

impl<F> Debug for Error<F>

where F: ErrorFormatter,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<F> Display for Error<F>

where F: ErrorFormatter,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<F> Error for Error<F>

where F: ErrorFormatter,

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl<F> From<Error> for Error<F>

where F: ErrorFormatter,

fn from(e: Error) -> Error<F>

Converts to this type from the input type.

impl<F> From<Error> for Error<F>

where F: ErrorFormatter,

fn from(e: Error) -> Error<F>

Converts to this type from the input type.