clap/src/parse/errors.rs

// Std
use std::{
    collections::VecDeque,
    convert::From,
    fmt::{self, Debug, Display, Formatter},
    io,
    result::Result as StdResult,
};

// Internal
use crate::{
    build::{Arg, ArgGroup},
    output::fmt::Colorizer,
    parse::features::suggestions,
    util::{safe_exit, termcolor::ColorChoice},
};

/// Short hand for [`Result`] type
///
/// [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
pub type Result<T> = StdResult<T, Error>;

/// Command line argument parser kind of error
#[derive(Debug, Copy, Clone, PartialEq)]
pub enum ErrorKind {
    /// Occurs when an [`Arg`] has a set of possible values,
    /// and the user provides a value which isn't in that set.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("speed")
    ///         .possible_value("fast")
    ///         .possible_value("slow"))
    ///     .try_get_matches_from(vec!["prog", "other"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::InvalidValue);
    /// ```
    /// [`Arg`]: ./struct.Arg.html
    InvalidValue,

    /// Occurs when a user provides a flag, option, argument or subcommand which isn't defined.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::from("--flag 'some flag'"))
    ///     .try_get_matches_from(vec!["prog", "--other"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::UnknownArgument);
    /// ```
    UnknownArgument,

    /// Occurs when the user provides an unrecognized [``] 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
    ///
    #[cfg_attr(not(feature = "suggestions"), doc = " ```no_run")]
    #[cfg_attr(feature = "suggestions", doc = " ```")]
    /// # use clap::{App, Arg, ErrorKind, };
    /// let result = App::new("prog")
    ///     .subcommand(App::new("config")
    ///         .about("Used for configuration")
    ///         .arg(Arg::with_name("config_file")
    ///             .help("The configuration file to use")
    ///             .index(1)))
    ///     .try_get_matches_from(vec!["prog", "confi"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::InvalidSubcommand);
    /// ```
    /// [``]: ./struct..html
    /// [`UnknownArgument`]: ./enum.ErrorKind.html#variant.UnknownArgument
    InvalidSubcommand,

    /// Occurs when the user provides an unrecognized [``] 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
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind, };
    /// let result = App::new("prog")
    ///     .subcommand(App::new("config")
    ///         .about("Used for configuration")
    ///         .arg(Arg::with_name("config_file")
    ///             .help("The configuration file to use")
    ///             .index(1)))
    ///     .try_get_matches_from(vec!["prog", "help", "nothing"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::UnrecognizedSubcommand);
    /// ```
    /// [``]: ./struct..html
    /// [`InvalidSubcommand`]: ./enum.ErrorKind.html#variant.InvalidSubcommand
    /// [`UnknownArgument`]: ./enum.ErrorKind.html#variant.UnknownArgument
    UnrecognizedSubcommand,

    /// Occurs when the user provides an empty value for an option that does not allow empty
    /// values.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind, ArgSettings};
    /// let res = App::new("prog")
    ///     .arg(Arg::with_name("color")
    ///          .setting(ArgSettings::TakesValue)
    ///          .long("color"))
    ///     .try_get_matches_from(vec!["prog", "--color="]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::EmptyValue);
    /// ```
    EmptyValue,

    /// Occurs when the user provides a value for an argument with a custom validation and the
    /// value fails that validation.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// fn is_numeric(val: String) -> Result<(), String> {
    ///     match val.parse::<i64>() {
    ///         Ok(..) => Ok(()),
    ///         Err(..) => Err(String::from("Value wasn't a number!")),
    ///     }
    /// }
    ///
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("num")
    ///          .validator(is_numeric))
    ///     .try_get_matches_from(vec!["prog", "NotANumber"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::ValueValidation);
    /// ```
    ValueValidation,

    /// Occurs when a user provides more values for an argument than were defined by setting
    /// [`Arg::max_values`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("arg")
    ///         .multiple(true)
    ///         .max_values(2))
    ///     .try_get_matches_from(vec!["prog", "too", "many", "values"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::TooManyValues);
    /// ```
    /// [`Arg::max_values`]: ./struct.Arg.html#method.max_values
    TooManyValues,

    /// Occurs when the user provides fewer values for an argument than were defined by setting
    /// [`Arg::min_values`].
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("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);
    /// ```
    /// [`Arg::min_values`]: ./struct.Arg.html#method.min_values
    TooFewValues,

    /// 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
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("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);
    /// ```
    ///
    /// [`Arg::number_of_values`]: ./struct.Arg.html#method.number_of_values
    /// [`Arg::value_names`]: ./struct.Arg.html#method.value_names
    WrongNumberOfValues,

    /// Occurs when the user provides two values which conflict with each other and can't be used
    /// together.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("debug")
    ///         .long("debug")
    ///         .conflicts_with("color"))
    ///     .arg(Arg::with_name("color")
    ///         .long("color"))
    ///     .try_get_matches_from(vec!["prog", "--debug", "--color"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::ArgumentConflict);
    /// ```
    ArgumentConflict,

    /// Occurs when the user does not provide one or more required arguments.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("debug")
    ///         .required(true))
    ///     .try_get_matches_from(vec!["prog"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
    /// ```
    MissingRequiredArgument,

    /// Occurs when a subcommand is required (as defined by [`AppSettings::SubcommandRequired`]),
    /// but the user does not provide one.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings, ErrorKind};
    /// let err = App::new("prog")
    ///     .setting(AppSettings::SubcommandRequired)
    ///     .subcommand(App::new("test"))
    ///     .try_get_matches_from(vec![
    ///         "myprog",
    ///     ]);
    /// assert!(err.is_err());
    /// assert_eq!(err.unwrap_err().kind, ErrorKind::MissingSubcommand);
    /// # ;
    /// ```
    /// [`AppSettings::SubcommandRequired`]: ./enum.AppSettings.html#variant.SubcommandRequired
    MissingSubcommand,

    /// Occurs when either an argument or [``] is required, as defined by
    /// [`AppSettings::ArgRequiredElseHelp`], but the user did not provide one.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, ErrorKind, };
    /// let result = App::new("prog")
    ///     .setting(AppSettings::ArgRequiredElseHelp)
    ///     .subcommand(App::new("config")
    ///         .about("Used for configuration")
    ///         .arg(Arg::with_name("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::MissingArgumentOrSubcommand);
    /// ```
    /// [``]: ./struct..html
    /// [`AppSettings::ArgRequiredElseHelp`]: ./enum.AppSettings.html#variant.ArgRequiredElseHelp
    MissingArgumentOrSubcommand,

    /// Occurs when the user provides multiple values to an argument which doesn't allow that.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .arg(Arg::with_name("debug")
    ///         .long("debug")
    ///         .multiple(false))
    ///     .try_get_matches_from(vec!["prog", "--debug", "--debug"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::UnexpectedMultipleUsage);
    /// ```
    UnexpectedMultipleUsage,

    /// Occurs when the user provides a value containing invalid UTF-8 for an argument and
    /// [`AppSettings::StrictUtf8`] is set.
    ///
    /// # Platform Specific
    ///
    /// Non-Windows platforms only (such as Linux, Unix, OSX, etc.)
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, Arg, ErrorKind, AppSettings};
    /// # use std::os::unix::ffi::OsStringExt;
    /// # use std::ffi::OsString;
    /// let result = App::new("prog")
    ///     .setting(AppSettings::StrictUtf8)
    ///     .arg(Arg::with_name("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);
    /// ```
    /// [`AppSettings::StrictUtf8`]: ./enum.AppSettings.html#variant.StrictUtf8
    InvalidUtf8,

    /// 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
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .try_get_matches_from(vec!["prog", "--help"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::HelpDisplayed);
    /// ```
    HelpDisplayed,

    /// Not a true "error" as it means `--version` or similar was used.
    /// The message will be sent to `stdout`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ErrorKind};
    /// let result = App::new("prog")
    ///     .try_get_matches_from(vec!["prog", "--version"]);
    /// assert!(result.is_err());
    /// assert_eq!(result.unwrap_err().kind, ErrorKind::VersionDisplayed);
    /// ```
    VersionDisplayed,

    /// Occurs when using the [`ArgMathes::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.
    ArgumentNotFound,

    /// Represents an [I/O error].
    /// Can occur when writing to `stderr` or `stdout` or reading a configuration file.
    /// [I/O error]: https://doc.rust-lang.org/std/io/struct.Error.html
    Io,

    /// Represents a [Format error] (which is a part of [`Display`]).
    /// Typically caused by writing to `stderr` or `stdout`.
    ///
    /// [`Display`]: https://doc.rust-lang.org/std/fmt/trait.Display.html
    /// [Format error]: https://doc.rust-lang.org/std/fmt/struct.Error.html
    Format,
}

/// Command Line Argument Parser Error
#[derive(Debug)]
pub struct Error {
    /// The cause of the error
    pub cause: String,
    /// Formatted error message, enhancing the cause message with extra information
    pub(crate) message: Colorizer,
    /// The type of error
    pub kind: ErrorKind,
    /// Any additional information passed along, such as the argument name that caused the error
    pub info: Option<Vec<String>>,
}

impl Display for Error {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        self.message.fmt(f)
    }
}

fn start_error(c: &mut Colorizer, msg: &str) -> io::Result<()> {
    c.error("error:")?;
    c.none(" ")?;
    c.none(msg)
}

fn put_usage<U>(c: &mut Colorizer, usage: U) -> io::Result<()>
where
    U: Display,
{
    c.none(&format!("\n\n{}", usage))
}

fn try_help(c: &mut Colorizer) -> io::Result<()> {
    c.none("\n\nFor more information try ")?;
    c.good("--help")?;
    c.none("\n")
}

impl Error {
    /// Returns the singular or plural form on the verb to be based on the argument's value.
    fn singular_or_plural(n: usize) -> String {
        if n > 1 {
            String::from("were")
        } else {
            String::from("was")
        }
    }

    /// Should the message be written to `stdout` or not
    #[inline]
    pub fn use_stderr(&self) -> bool {
        match self.kind {
            ErrorKind::HelpDisplayed | ErrorKind::VersionDisplayed => false,
            _ => true,
        }
    }

    /// Prints the error to `stderr` and exits with a status of `1`
    pub fn exit(&self) -> ! {
        if self.use_stderr() {
            self.message.print().expect("Error writing Error to stderr");
            process::exit(1);
        }

        self.message.print().expect("Error writing Error to stdout");
        process::exit(0);
    }

    #[allow(unused)] // requested by @pksunkara
    pub(crate) fn group_conflict<O, U>(
        group: &ArgGroup,
        other: Option<O>,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        O: Into<String>,
        U: Display,
    {
        let mut v = vec![group.name.to_owned()];
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The argument '")?;
        c.warning(group.name)?;
        c.none("' cannot be used with ")?;

        let cause = match other {
            Some(name) => {
                let n = name.into();
                v.push(n.clone());

                c.none("'")?;
                c.warning(&*n)?;
                c.none("'")?;

                format!("The argument '{}' cannot be used with '{}'", group.name, n)
            }
            None => {
                let n = "one or more of the other specified arguments";

                c.none(n)?;

                format!("The argument '{}' cannot be used with {}", group.name, n)
            }
        };

        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause,
            message: c,
            kind: ErrorKind::ArgumentConflict,
            info: Some(v),
        })
    }

    pub(crate) fn argument_conflict<O, U>(
        arg: &Arg,
        other: Option<O>,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        O: Into<String>,
        U: Display,
    {
        let mut v = vec![arg.name.to_owned()];
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The argument '")?;
        c.warning(&arg.to_string())?;
        c.none("' cannot be used with ")?;

        let cause = match other {
            Some(name) => {
                let n = name.into();
                v.push(n.clone());

                c.none("'")?;
                c.warning(&*n)?;
                c.none("'")?;

                format!("The argument '{}' cannot be used with '{}'", arg, n)
            }
            None => {
                let n = "one or more of the other specified arguments";

                c.none(n)?;

                format!("The argument '{}' cannot be used with {}", arg, n)
            }
        };

        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause,
            message: c,
            kind: ErrorKind::ArgumentConflict,
            info: Some(v),
        })
    }

    pub(crate) fn empty_value<U>(arg: &Arg, usage: U, color: ColorChoice) -> io::Result<Self>
    where
        U: Display,
    {
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The argument '")?;
        c.warning(&arg.to_string())?;
        c.none("' requires a value but none was supplied")?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "The argument '{}' requires a value but none was supplied",
                arg
            ),
            message: c,
            kind: ErrorKind::EmptyValue,
            info: Some(vec![arg.name.to_owned()]),
        })
    }

    pub(crate) fn invalid_value<B, G, U>(
        bad_val: B,
        good_vals: &[G],
        arg: &Arg,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        B: AsRef<str>,
        G: AsRef<str> + Display,
        U: Display,
    {
        let mut c = Colorizer::new(true, color);
        let suffix = suggestions::did_you_mean(bad_val.as_ref(), good_vals.iter()).pop();

        let mut sorted: Vec<String> = good_vals.iter().map(|v| v.to_string()).collect();
        sorted.sort();

        start_error(&mut c, "'")?;
        c.warning(bad_val.as_ref())?;
        c.none("' isn't a valid value for '")?;
        c.warning(&arg.to_string())?;
        c.none("'\n\t[possible values: ")?;

        if let Some((last, elements)) = sorted.split_last() {
            for v in elements {
                c.good(v)?;
                c.none(", ")?;
            }

            c.good(last)?;
        }

        c.none("]")?;

        if let Some(val) = suffix {
            c.none("\n\n\tDid you mean '")?;
            c.good(&val)?;
            c.none("'?")?;
        }

        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "'{}' isn't a valid value for '{}'\n\t\
                 [possible values: {}]",
                bad_val.as_ref(),
                arg,
                sorted.join(", ")
            ),
            message: c,
            kind: ErrorKind::InvalidValue,
            info: Some(vec![arg.name.to_owned(), bad_val.as_ref().to_owned()]),
        })
    }

    pub(crate) fn invalid_subcommand<S, D, N, U>(
        subcmd: S,
        did_you_mean: D,
        name: N,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        S: Into<String>,
        D: AsRef<str> + Display,
        N: Display,
        U: Display,
    {
        let s = subcmd.into();
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The subcommand '")?;
        c.warning(&*s)?;
        c.none("' wasn't recognized\n\n\tDid you mean ")?;
        c.good(did_you_mean.as_ref())?;
        c.none("")?;
        c.none(&format!(
            "?\n\nIf you believe you received this message in error, try re-running with '{} ",
            name
        ))?;
        c.good("--")?;
        c.none(&format!(" {}'", &*s))?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!("The subcommand '{}' wasn't recognized", s),
            message: c,
            kind: ErrorKind::InvalidSubcommand,
            info: Some(vec![s]),
        })
    }

    pub(crate) fn unrecognized_subcommand<S, N>(
        subcmd: S,
        name: N,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        S: Into<String>,
        N: Display,
    {
        let s = subcmd.into();
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, " The subcommand '")?;
        c.warning(&*s)?;
        c.none("' wasn't recognized\n\n")?;
        c.warning("USAGE:")?;
        c.none(&format!("\n\t{} help <subcommands>...", name))?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!("The subcommand '{}' wasn't recognized", s),
            message: c,
            kind: ErrorKind::UnrecognizedSubcommand,
            info: Some(vec![s]),
        })
    }

    pub(crate) fn missing_required_argument<R, U>(
        required: VecDeque<R>,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        R: Display,
        U: Display,
    {
        let mut c = Colorizer::new(true, color);

        let cause = format!(
            "The following required arguments were not provided:{}",
            required
                .iter()
                .map(|x| format!("\n    {}", x))
                .collect::<Vec<_>>()
                .join(""),
        );

        start_error(
            &mut c,
            "The following required arguments were not provided:",
        )?;

        for v in required {
            c.none("\n    ")?;
            c.good(&v.to_string())?;
        }

        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause,
            message: c,
            kind: ErrorKind::MissingRequiredArgument,
            info: None,
        })
    }

    pub(crate) fn missing_subcommand<N, U>(
        name: N,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        N: AsRef<str> + Display,
        U: Display,
    {
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "'")?;
        c.warning(name.as_ref())?;
        c.none("' requires a subcommand, but one was not provided")?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!("'{}' requires a subcommand, but one was not provided", name),
            message: c,
            kind: ErrorKind::MissingSubcommand,
            info: None,
        })
    }

    pub(crate) fn invalid_utf8<U>(usage: U, color: ColorChoice) -> io::Result<Self>
    where
        U: Display,
    {
        let mut c = Colorizer::new(true, color);

        let cause = "Invalid UTF-8 was detected in one or more arguments";

        start_error(&mut c, cause)?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: cause.to_string(),
            message: c,
            kind: ErrorKind::InvalidUtf8,
            info: None,
        })
    }

    pub(crate) fn too_many_values<V, U>(
        val: V,
        arg: &Arg,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        V: AsRef<str> + Display + ToOwned,
        U: Display,
    {
        let v = val.as_ref();
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The value '")?;
        c.warning(v)?;
        c.none("' was provided to '")?;
        c.warning(&arg.to_string())?;
        c.none("' but it wasn't expecting any more values")?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "The value '{}' was provided to '{}', but it wasn't expecting any more values",
                v, arg
            ),
            message: c,
            kind: ErrorKind::TooManyValues,
            info: Some(vec![arg.name.to_owned(), v.to_owned()]),
        })
    }

    pub(crate) fn too_few_values<U>(
        arg: &Arg,
        min_vals: u64,
        curr_vals: usize,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        U: Display,
    {
        let mut c = Colorizer::new(true, color);
        let verb = Error::singular_or_plural(curr_vals);

        start_error(&mut c, "The argument '")?;
        c.warning(&arg.to_string())?;
        c.none("' requires at least ")?;
        c.warning(&min_vals.to_string())?;
        c.none("values, but only ")?;
        c.warning(&curr_vals.to_string())?;
        c.none(&format!(" {} provided", verb))?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "The argument '{}' requires at least {} values, but only {} {} provided",
                arg, min_vals, curr_vals, verb
            ),
            message: c,
            kind: ErrorKind::TooFewValues,
            info: Some(vec![arg.name.to_owned()]),
        })
    }

    pub(crate) fn value_validation(
        arg: Option<&Arg>,
        err: &str,
        color: ColorChoice,
    ) -> io::Result<Self> {
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "Invalid value")?;

        if let Some(a) = arg {
            c.none(" for '")?;
            c.warning(&a.to_string())?;
            c.none("'")?;
        }

        c.none(&format!(": {}", err))?;

        Ok(Error {
            cause: format!(
                "Invalid value{}: {}",
                if let Some(a) = arg {
                    format!(" for '{}'", a)
                } else {
                    String::new()
                },
                err
            ),
            message: c,
            kind: ErrorKind::ValueValidation,
            info: None,
        })
    }

    pub(crate) fn value_validation_auto(err: &str) -> io::Result<Self> {
        let n: Option<&Arg> = None;
        Error::value_validation(n, err, ColorChoice::Auto)
    }

    pub(crate) fn wrong_number_of_values<U>(
        arg: &Arg,
        num_vals: u64,
        curr_vals: usize,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        U: Display,
    {
        let mut c = Colorizer::new(true, color);
        let verb = Error::singular_or_plural(curr_vals);

        start_error(&mut c, "The argument '")?;
        c.warning(&arg.to_string())?;
        c.none("' requires ")?;
        c.warning(&num_vals.to_string())?;
        c.none(" values, but ")?;
        c.warning(&curr_vals.to_string())?;
        c.none(&format!(" {} provided", verb))?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "The argument '{}' requires {} values, but {} {} provided",
                arg, num_vals, curr_vals, verb
            ),
            message: c,
            kind: ErrorKind::WrongNumberOfValues,
            info: Some(vec![arg.name.to_owned()]),
        })
    }

    pub(crate) fn unexpected_multiple_usage<U>(
        arg: &Arg,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        U: Display,
    {
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "The argument '")?;
        c.warning(&arg.to_string())?;
        c.none("' was provided more than once, but cannot be used multiple times")?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "The argument '{}' was provided more than once, but cannot be used multiple times",
                arg
            ),
            message: c,
            kind: ErrorKind::UnexpectedMultipleUsage,
            info: Some(vec![arg.name.to_owned()]),
        })
    }

    pub(crate) fn unknown_argument<A, U>(
        arg: A,
        did_you_mean: Option<(String, Option<String>)>,
        usage: U,
        color: ColorChoice,
    ) -> io::Result<Self>
    where
        A: Into<String>,
        U: Display,
    {
        let a = arg.into();
        let mut c = Colorizer::new(true, color);

        start_error(&mut c, "Found argument '")?;
        c.warning(&*a)?;
        c.none("' which wasn't expected, or isn't valid in this context")?;

        if let Some(s) = did_you_mean {
            c.none("\n\n\tDid you mean ")?;

            if let Some(subcmd) = s.1 {
                c.none("to put '")?;
                c.good(&format!("--{}", &s.0))?;
                c.none("' after the subcommand '")?;
                c.good(&subcmd)?;
                c.none("'?")?;
            } else {
                c.none("'")?;
                c.good(&format!("--{}", &s.0))?;
                c.none("'?")?;
            }
        }

        c.none(&format!(
            "\n\nIf you tried to supply `{}` as a PATTERN use `-- {}`",
            a, a
        ))?;
        put_usage(&mut c, usage)?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!(
                "Found argument '{}' which wasn't expected, or isn't valid in this context",
                a
            ),
            message: c,
            kind: ErrorKind::UnknownArgument,
            info: Some(vec![a]),
        })
    }

    pub(crate) fn argument_not_found_auto<A>(arg: A) -> io::Result<Self>
    where
        A: Into<String>,
    {
        let a = arg.into();
        let mut c = Colorizer::new(true, ColorChoice::Auto);

        start_error(&mut c, "The argument '")?;
        c.warning(&*a)?;
        c.none("' wasn't found")?;
        try_help(&mut c)?;

        Ok(Error {
            cause: format!("The argument '{}' wasn't found", a),
            message: c,
            kind: ErrorKind::ArgumentNotFound,
            info: Some(vec![a]),
        })
    }

    /// Create an error with a custom description.
    ///
    /// This can be used in combination with `Error::exit` to exit your program
    /// with a custom error message.
    pub fn with_description(description: impl Into<String>, kind: ErrorKind) -> io::Result<Self> {
        let mut c = Colorizer::new(true, ColorChoice::Auto);

        let cause = description.into();

        start_error(&mut c, &*cause)?;

        Ok(Error {
            cause,
            message: c,
            kind,
            info: None,
        })
    }
}

impl From<io::Error> for Error {
    fn from(e: io::Error) -> Self {
        Error::with_description(e.to_string(), ErrorKind::Io)
            .expect("Unable to build error message")
    }
}

impl From<fmt::Error> for Error {
    fn from(e: fmt::Error) -> Self {
        Error::with_description(e.to_string(), ErrorKind::Format)
            .expect("Unable to build error message")
    }
}