Enum ParseError 

#[non_exhaustive]
pub enum ParseError {
    UnknownFlag {
        flag: String,
    },
    MissingValue {
        option: String,
    },
    MissingRequired {
        arg: String,
    },
    UnknownCommand {
        name: String,
    },
    UnexpectedArgument {
        value: String,
    },
    HelpRequested(String),
    VersionRequested(String),
    Unauthorized {
        command: String,
    },
}

Available on crate feature std only.

A failure to parse command-line arguments.

Returned by App::try_parse_from. The variants are marked #[non_exhaustive] so future versions can add cases (for example, as the help and auth seams land) without a breaking change.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

UnknownFlag

A -x / --name flag was given that no argument at this level declares.

Fields

flag: String

The flag as the user wrote it, e.g. --verbsoe.

MissingValue

An option that takes a value was given without one (it was the last token, or followed only by another option).

Fields

option: String

The option’s name.

MissingRequired

A required argument was not provided.

Fields

arg: String

The missing argument’s name.

UnknownCommand

A subcommand name was expected but the token matched no registered command.

Fields

name: String

The unrecognized command name.

UnexpectedArgument

A bare value was given that no positional argument or subcommand can accept.

Fields

value: String

The surplus value.

HelpRequested(String)

Not an error: -h / --help was requested. Carries the rendered help text. App::parse prints it to standard output and exits 0; callers of App::try_parse_from should do the same.

VersionRequested(String)

Not an error: -V / --version was requested. Carries the version string. Handled like HelpRequested.

Unauthorized

An auth-gated command (Command::requires_auth) was invoked but the app’s auth hook did not authorize it (or no hook was set). Produced only with the auth feature enabled; the command’s handler does not run.

Fields

command: String

The command that was refused.

Trait Implementations

impl Clone for ParseError

fn clone(&self) -> ParseError

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ParseError

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

Formats the value using the given formatter.

impl Display for ParseError

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

Formats the value using the given formatter.

impl Eq for ParseError

impl Error for ParseError

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 PartialEq for ParseError

fn eq(&self, other: &ParseError) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for ParseError