Enum Error 

pub enum Error {
    UnknownOption(String),
    UnknownSubcommand {
        name: String,
        available: Vec<String>,
    },
    MissingValue(String),
    UnexpectedValue(String),
    MissingOption(String),
    MissingArgument(String),
    MissingSubcommand {
        available: Vec<String>,
    },
    ExtraArgument(String),
    InvalidValue {
        name: String,
        value: String,
        message: String,
    },
    HelpRequested,
    InSubcommand {
        path: Vec<String>,
        source: Box<Error>,
    },
    Runtime(Box<Error>),
    Custom(String),
}

Errors produced by the launcher when parsing command-line arguments.

Variants

UnknownOption(String)

UnknownSubcommand

Fields

name: String

available: Vec<String>

MissingValue(String)

UnexpectedValue(String)

MissingOption(String)

A required option was not provided at all (distinct from MissingValue, which fires when the option name was typed without a following value).

MissingArgument(String)

MissingSubcommand

Fields

available: Vec<String>

ExtraArgument(String)

InvalidValue

Fields

name: String

value: String

message: String

HelpRequested

Sentinel used internally when the user passes -h/--help.

InSubcommand

Wraps an error produced while parsing a subcommand so the launcher can print the right (sub)command help. path is the chain from the root schema to the failing subcommand, newest-last.

Fields

path: Vec<String>

source: Box<Error>

Runtime(Box<Error>)

Wraps an error returned by a subcommand’s run method. The launcher uses this to distinguish user runtime failures from parse-origin errors. It matters because SubCommandOf::run may legitimately reuse parse-origin variants (e.g. MissingArgument) for its own post-parse validation, so variant-based classification alone is not enough.

Custom(String)

Implementations

impl Error

pub fn invalid_value( name: impl Into<String>, value: impl Into<String>, message: impl Into<String>, ) -> Self

pub fn custom(message: impl Into<String>) -> Self

pub fn is_parse_error(&self) -> bool

Whether this error originated from argument parsing (as opposed to a user command’s runtime logic). The launcher uses this to decide whether to print help text alongside the error message.

Trait Implementations

impl Debug for Error

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

Formats the value using the given formatter.

impl Display for Error

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

Formats the value using the given formatter.

impl Error for Error

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.