# Struct clap::error::Error

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    pub struct Error<F: ErrorFormatter = DefaultFormatter> { /* private fields */ }

Expand description

Command Line Argument Parser Error

See `Command::error` to create an error.

## Implementations

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### impl<F: ErrorFormatter> Error<F>

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#### pub 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.

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

Format the existing message with the Command’s context

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#### pub fn new(kind: ErrorKind) -> Self

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();

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

Apply `Command`’s formatting to the error

Generally, this is used with `Error::new`

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

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());

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#### pub fn kind(&self) -> ErrorKind

Type of error for programmatic processing

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

Additional information to further qualify the error

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

Lookup a piece of context

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

Insert a piece of context

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#### pub fn use_stderr(&self) -> bool

Should the message be written to `stdout` or not?

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#### 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`.

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

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
        },
    };

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#### 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

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### impl<F: ErrorFormatter> Debug for Error<F>

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

Formats the value using the given formatter. Read more

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### impl<F: ErrorFormatter> Display for Error<F>

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

Formats the value using the given formatter. Read more

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### impl<F: ErrorFormatter> Error for Error<F>

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

The lower-level source of this error, if any. Read more

1.0.0 · source

#### fn description(&self) -> &str

👎 Deprecated since 1.42.0:

use the Display impl or to_string()

Read more
1.0.0 · source

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

👎 Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

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#### fn provide(&'a self, req: &mut Demand<'a>)

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

Provides type based access to context intended for error reports. Read more

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### impl<F: ErrorFormatter> From<Error> for Error<F>

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#### fn from(e: Error) -> Self

Converts to this type from the input type.

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### impl<F: ErrorFormatter> From<Error> for Error<F>

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#### fn from(e: Error) -> Self

Converts to this type from the input type.

## Auto Trait Implementations

### impl<F = RichFormatter> !RefUnwindSafe for Error<F>

### impl<F> Send for Error<F> where
F: Send,

### impl<F> Sync for Error<F> where
F: Sync,

### impl<F> Unpin for Error<F> where
F: Unpin,

### impl<F = RichFormatter> !UnwindSafe for Error<F>

## Blanket Implementations

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToString for T where
T: Display + ?Sized,

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#### default fn to_string(&self) -> String

Converts the given value to a `String`. Read more

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.