impl<F: ErrorFormatter> Error<F>

fn raw(kind: ErrorKind, message: impl Display) -> Self

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.

fn format(self, cmd: &mut Command) -> Self

Format the existing message with the Command's context

fn new(kind: ErrorKind) -> Self

Create an error with a pre-defined message

See also

• Error::insert
• Error::with_cmd

Example

# #[cfg(feature = "error-context")] {
# use clap_builder as clap;
# use clap::error::ErrorKind;
# use clap::error::ContextKind;
# use clap::error::ContextValue;

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();
# }

fn with_cmd(self, cmd: &Command) -> Self

Apply Command's formatting to the error

Generally, this is used with Error::new

fn apply<EF: ErrorFormatter>(self) -> Error<EF>

Apply an alternative formatter to the error

Example

# use clap_builder as clap;
# use clap::Command;
# use clap::Arg;
# use clap::error::KindFormatter;
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());

fn kind(&self) -> ErrorKind

Type of error for programmatic processing

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

Additional information to further qualify the error

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

Lookup a piece of context

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

Insert a piece of context

If this ContextKind is already present, its value is replaced and the old value is returned.

fn remove(&mut self, kind: ContextKind) -> Option<ContextValue>

Remove a piece of context, return the old value if any

The context is currently implemented in a vector, so remove takes linear time.

fn use_stderr(&self) -> bool

Should the message be written to stdout or not?

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.

fn exit(&self) -> never

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.

fn print(&self) -> Result<()>

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

Example

# use clap_builder as clap;
use clap::Command;

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

fn render(&self) -> StyledStr

Render the error message to a StyledStr.

Example

# use clap_builder as clap;
use clap::Command;

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