#[non_exhaustive]
pub enum ErrorKind {
Show 22 variants
InvalidValue,
UnknownArgument,
InvalidSubcommand,
UnrecognizedSubcommand,
EmptyValue,
NoEquals,
ValueValidation,
TooManyValues,
TooFewValues,
TooManyOccurrences,
WrongNumberOfValues,
ArgumentConflict,
MissingRequiredArgument,
MissingSubcommand,
UnexpectedMultipleUsage,
InvalidUtf8,
DisplayHelp,
DisplayHelpOnMissingArgumentOrSubcommand,
DisplayVersion,
ArgumentNotFound,
Io,
Format,
}
Expand description
Command line argument parser kind of error
Variants (Non-exhaustive)§
This enum is marked as non-exhaustive
InvalidValue
Occurs when an Arg
has a set of possible values,
and the user provides a value which isn’t in that set.
Examples
let result = Command::new("prog")
.arg(Arg::new("speed")
.value_parser(["fast", "slow"]))
.try_get_matches_from(vec!["prog", "other"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::InvalidValue);
UnknownArgument
Occurs when a user provides a flag, option, argument or subcommand which isn’t defined.
Examples
let result = Command::new("prog")
.arg(arg!(--flag "some flag"))
.try_get_matches_from(vec!["prog", "--other"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::UnknownArgument);
InvalidSubcommand
Occurs when the user provides an unrecognized Subcommand
which meets the threshold for
being similar enough to an existing subcommand.
If it doesn’t meet the threshold, or the ‘suggestions’ feature is disabled,
the more general UnknownArgument
error is returned.
Examples
let result = Command::new("prog")
.subcommand(Command::new("config")
.about("Used for configuration")
.arg(Arg::new("config_file")
.help("The configuration file to use")))
.try_get_matches_from(vec!["prog", "confi"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::InvalidSubcommand);
UnrecognizedSubcommand
Occurs when the user provides an unrecognized Subcommand
which either
doesn’t meet the threshold for being similar enough to an existing subcommand,
or the ‘suggestions’ feature is disabled.
Otherwise the more detailed InvalidSubcommand
error is returned.
This error typically happens when passing additional subcommand names to the help
subcommand. Otherwise, the more general UnknownArgument
error is used.
Examples
let result = Command::new("prog")
.subcommand(Command::new("config")
.about("Used for configuration")
.arg(Arg::new("config_file")
.help("The configuration file to use")))
.try_get_matches_from(vec!["prog", "help", "nothing"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::UnrecognizedSubcommand);
EmptyValue
Occurs when the user provides an empty value for an option that does not allow empty values.
Examples
let res = Command::new("prog")
.arg(Arg::new("color")
.takes_value(true)
.forbid_empty_values(true)
.long("color"))
.try_get_matches_from(vec!["prog", "--color="]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind(), ErrorKind::EmptyValue);
NoEquals
Occurs when the user doesn’t use equals for an option that requires equal sign to provide values.
let res = Command::new("prog")
.arg(Arg::new("color")
.takes_value(true)
.require_equals(true)
.long("color"))
.try_get_matches_from(vec!["prog", "--color", "red"]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind(), ErrorKind::NoEquals);
ValueValidation
Occurs when the user provides a value for an argument with a custom validation and the value fails that validation.
Examples
fn is_numeric(val: &str) -> Result<(), String> {
match val.parse::<i64>() {
Ok(..) => Ok(()),
Err(..) => Err(String::from("Value wasn't a number!")),
}
}
let result = Command::new("prog")
.arg(Arg::new("num")
.validator(is_numeric))
.try_get_matches_from(vec!["prog", "NotANumber"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::ValueValidation);
TooManyValues
Occurs when a user provides more values for an argument than were defined by setting
Arg::max_values
.
Examples
let result = Command::new("prog")
.arg(Arg::new("arg")
.max_values(2))
.try_get_matches_from(vec!["prog", "too", "many", "values"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::TooManyValues);
TooFewValues
Occurs when the user provides fewer values for an argument than were defined by setting
Arg::min_values
.
Examples
let result = Command::new("prog")
.arg(Arg::new("some_opt")
.long("opt")
.min_values(3))
.try_get_matches_from(vec!["prog", "--opt", "too", "few"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::TooFewValues);
TooManyOccurrences
Occurs when a user provides more occurrences for an argument than were defined by setting
Arg::max_occurrences
.
Examples
let result = Command::new("prog")
.arg(Arg::new("verbosity")
.short('v')
.max_occurrences(2))
.try_get_matches_from(vec!["prog", "-vvv"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::TooManyOccurrences);
WrongNumberOfValues
Occurs when the user provides a different number of values for an argument than what’s
been defined by setting Arg::number_of_values
or than was implicitly set by
Arg::value_names
.
Examples
let result = Command::new("prog")
.arg(Arg::new("some_opt")
.long("opt")
.takes_value(true)
.number_of_values(2))
.try_get_matches_from(vec!["prog", "--opt", "wrong"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::WrongNumberOfValues);
ArgumentConflict
Occurs when the user provides two values which conflict with each other and can’t be used together.
Examples
let result = Command::new("prog")
.arg(Arg::new("debug")
.long("debug")
.conflicts_with("color"))
.arg(Arg::new("color")
.long("color"))
.try_get_matches_from(vec!["prog", "--debug", "--color"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::ArgumentConflict);
MissingRequiredArgument
Occurs when the user does not provide one or more required arguments.
Examples
let result = Command::new("prog")
.arg(Arg::new("debug")
.required(true))
.try_get_matches_from(vec!["prog"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::MissingRequiredArgument);
MissingSubcommand
Occurs when a subcommand is required (as defined by Command::subcommand_required
),
but the user does not provide one.
Examples
let err = Command::new("prog")
.subcommand_required(true)
.subcommand(Command::new("test"))
.try_get_matches_from(vec![
"myprog",
]);
assert!(err.is_err());
assert_eq!(err.unwrap_err().kind(), ErrorKind::MissingSubcommand);
UnexpectedMultipleUsage
Occurs when the user provides multiple values to an argument which doesn’t allow that.
Examples
let result = Command::new("prog")
.arg(Arg::new("debug")
.long("debug")
.multiple_occurrences(false))
.try_get_matches_from(vec!["prog", "--debug", "--debug"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::UnexpectedMultipleUsage);
InvalidUtf8
Occurs when the user provides a value containing invalid UTF-8.
To allow arbitrary data
- Set
Arg::allow_invalid_utf8
for argument values - Set
Command::allow_invalid_utf8_for_external_subcommands
for external-subcommand values
Platform Specific
Non-Windows platforms only (such as Linux, Unix, OSX, etc.)
Examples
let result = Command::new("prog")
.arg(Arg::new("utf8")
.short('u')
.takes_value(true))
.try_get_matches_from(vec![OsString::from("myprog"),
OsString::from("-u"),
OsString::from_vec(vec![0xE9])]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::InvalidUtf8);
DisplayHelp
Not a true “error” as it means --help
or similar was used.
The help message will be sent to stdout
.
Note: If the help is displayed due to an error (such as missing subcommands) it will
be sent to stderr
instead of stdout
.
Examples
let result = Command::new("prog")
.try_get_matches_from(vec!["prog", "--help"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::DisplayHelp);
DisplayHelpOnMissingArgumentOrSubcommand
Occurs when either an argument or a Subcommand
is required, as defined by
Command::arg_required_else_help
, but the user did not provide
one.
Examples
let result = Command::new("prog")
.arg_required_else_help(true)
.subcommand(Command::new("config")
.about("Used for configuration")
.arg(Arg::new("config_file")
.help("The configuration file to use")))
.try_get_matches_from(vec!["prog"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand);
DisplayVersion
Not a true “error” as it means --version
or similar was used.
The message will be sent to stdout
.
Examples
let result = Command::new("prog")
.version("3.0")
.try_get_matches_from(vec!["prog", "--version"]);
assert!(result.is_err());
assert_eq!(result.unwrap_err().kind(), ErrorKind::DisplayVersion);
ArgumentNotFound
Occurs when using the ArgMatches::value_of_t
and friends to convert an argument value
into type T
, but the argument you requested wasn’t used. I.e. you asked for an argument
with name config
to be converted, but config
wasn’t used by the user.
Io
Represents an I/O error.
Can occur when writing to stderr
or stdout
or reading a configuration file.
Format
Represents a Format error (which is a part of Display
).
Typically caused by writing to stderr
or stdout
.