Enum BuildError 

pub enum BuildError {
    EmptyCanonical,
    DuplicateAlias(String),
    AliasEqualsCanonical(String),
    DuplicateFlagName(String),
    DuplicateShortFlag(char),
    DuplicateArgumentName(String),
    DuplicateSubcommandName(String),
    VariadicNotLast(String),
    EmptyChoices(String),
    ExclusiveGroupTooSmall,
    ExclusiveGroupUnknownFlag(String),
}

Error returned by builder build() methods.

Variants are returned from CommandBuilder::build, ArgumentBuilder::build, and FlagBuilder::build when validation fails. The list of variants includes checks for empty names, duplicate aliases, duplicate flags, duplicate arguments, duplicate subcommands, and variadic argument ordering.

Examples

assert_eq!(Command::builder("").build().unwrap_err(), BuildError::EmptyCanonical);

Variants

EmptyCanonical

The canonical name (or argument/flag name) was empty or whitespace.

DuplicateAlias(String)

Two aliases on the same command share the same string.

AliasEqualsCanonical(String)

An alias is identical to the command’s canonical name.

DuplicateFlagName(String)

Two flags on the same command share the same long name.

DuplicateShortFlag(char)

Two flags on the same command share the same short character.

DuplicateArgumentName(String)

Two positional arguments on the same command share the same name.

DuplicateSubcommandName(String)

Two subcommands at the same level share the same canonical name.

VariadicNotLast(String)

A variadic argument is not the last argument defined.

EmptyChoices(String)

A flag’s choices list is empty, which would reject all values.

ExclusiveGroupTooSmall

A mutual-exclusivity group contains fewer than two flag names.

ExclusiveGroupUnknownFlag(String)

A flag referenced in a mutual-exclusivity group is not defined on the command.

Trait Implementations

impl Debug for BuildError

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

Formats the value using the given formatter.

impl Display for BuildError

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

Formats the value using the given formatter.

impl Error for BuildError

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 BuildError

fn eq(&self, other: &BuildError) -> 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 BuildError