src/app/settings.rs

// Std
#[allow(deprecated, unused_imports)]
use std::ascii::AsciiExt;
use std::ops::BitOr;
use std::str::FromStr;

bitflags! {
    struct Flags: u64 {
        const SC_NEGATE_REQS       = 1;
        const SC_REQUIRED          = 1 << 1;
        const A_REQUIRED_ELSE_HELP = 1 << 2;
        const GLOBAL_VERSION       = 1 << 3;
        const VERSIONLESS_SC       = 1 << 4;
        const UNIFIED_HELP         = 1 << 5;
        const WAIT_ON_ERROR        = 1 << 6;
        const SC_REQUIRED_ELSE_HELP= 1 << 7;
        const NEEDS_LONG_HELP      = 1 << 8;
        const NEEDS_LONG_VERSION   = 1 << 9;
        const NEEDS_SC_HELP        = 1 << 10;
        const DISABLE_VERSION      = 1 << 11;
        const HIDDEN               = 1 << 12;
        const TRAILING_VARARG      = 1 << 13;
        const NO_BIN_NAME          = 1 << 14;
        const ALLOW_UNK_SC         = 1 << 15;
        const UTF8_STRICT          = 1 << 16;
        const UTF8_NONE            = 1 << 17;
        const LEADING_HYPHEN       = 1 << 18;
        const NO_POS_VALUES        = 1 << 19;
        const NEXT_LINE_HELP       = 1 << 20;
        const DERIVE_DISP_ORDER    = 1 << 21;
        const COLORED_HELP         = 1 << 22;
        const COLOR_ALWAYS         = 1 << 23;
        const COLOR_AUTO           = 1 << 24;
        const COLOR_NEVER          = 1 << 25;
        const DONT_DELIM_TRAIL     = 1 << 26;
        const ALLOW_NEG_NUMS       = 1 << 27;
        const LOW_INDEX_MUL_POS    = 1 << 28;
        const DISABLE_HELP_SC      = 1 << 29;
        const DONT_COLLAPSE_ARGS   = 1 << 30;
        const ARGS_NEGATE_SCS      = 1 << 31;
        const PROPAGATE_VALS_DOWN  = 1 << 32;
        const ALLOW_MISSING_POS    = 1 << 33;
        const TRAILING_VALUES      = 1 << 34;
        const VALID_NEG_NUM_FOUND  = 1 << 35;
        const PROPAGATED           = 1 << 36;
        const VALID_ARG_FOUND      = 1 << 37;
        const INFER_SUBCOMMANDS    = 1 << 38;
        const CONTAINS_LAST        = 1 << 39;
        const ARGS_OVERRIDE_SELF   = 1 << 40;
        const DISABLE_HELP_FLAGS   = 1 << 41;
    }
}

#[doc(hidden)]
#[derive(Debug, Copy, Clone, PartialEq)]
pub struct AppFlags(Flags);

impl BitOr for AppFlags {
    type Output = Self;
    fn bitor(self, rhs: Self) -> Self {
        AppFlags(self.0 | rhs.0)
    }
}

impl Default for AppFlags {
    fn default() -> Self {
        AppFlags(
            Flags::NEEDS_LONG_VERSION
                | Flags::NEEDS_LONG_HELP
                | Flags::NEEDS_SC_HELP
                | Flags::UTF8_NONE
                | Flags::COLOR_AUTO,
        )
    }
}

#[allow(deprecated)]
impl AppFlags {
    pub fn new() -> Self {
        AppFlags::default()
    }
    pub fn zeroed() -> Self {
        AppFlags(Flags::empty())
    }

    impl_settings! { AppSettings,
        ArgRequiredElseHelp => Flags::A_REQUIRED_ELSE_HELP,
        ArgsNegateSubcommands => Flags::ARGS_NEGATE_SCS,
        AllArgsOverrideSelf => Flags::ARGS_OVERRIDE_SELF,
        AllowExternalSubcommands => Flags::ALLOW_UNK_SC,
        AllowInvalidUtf8 => Flags::UTF8_NONE,
        AllowLeadingHyphen => Flags::LEADING_HYPHEN,
        AllowNegativeNumbers => Flags::ALLOW_NEG_NUMS,
        AllowMissingPositional => Flags::ALLOW_MISSING_POS,
        ColoredHelp => Flags::COLORED_HELP,
        ColorAlways => Flags::COLOR_ALWAYS,
        ColorAuto => Flags::COLOR_AUTO,
        ColorNever => Flags::COLOR_NEVER,
        DontDelimitTrailingValues => Flags::DONT_DELIM_TRAIL,
        DontCollapseArgsInUsage => Flags::DONT_COLLAPSE_ARGS,
        DeriveDisplayOrder => Flags::DERIVE_DISP_ORDER,
        DisableHelpFlags => Flags::DISABLE_HELP_FLAGS,
        DisableHelpSubcommand => Flags::DISABLE_HELP_SC,
        DisableVersion => Flags::DISABLE_VERSION,
        GlobalVersion => Flags::GLOBAL_VERSION,
        HidePossibleValuesInHelp => Flags::NO_POS_VALUES,
        Hidden => Flags::HIDDEN,
        LowIndexMultiplePositional => Flags::LOW_INDEX_MUL_POS,
        NeedsLongHelp => Flags::NEEDS_LONG_HELP,
        NeedsLongVersion => Flags::NEEDS_LONG_VERSION,
        NeedsSubcommandHelp => Flags::NEEDS_SC_HELP,
        NoBinaryName => Flags::NO_BIN_NAME,
        PropagateGlobalValuesDown=> Flags::PROPAGATE_VALS_DOWN,
        StrictUtf8 => Flags::UTF8_STRICT,
        SubcommandsNegateReqs => Flags::SC_NEGATE_REQS,
        SubcommandRequired => Flags::SC_REQUIRED,
        SubcommandRequiredElseHelp => Flags::SC_REQUIRED_ELSE_HELP,
        TrailingVarArg => Flags::TRAILING_VARARG,
        UnifiedHelpMessage => Flags::UNIFIED_HELP,
        NextLineHelp => Flags::NEXT_LINE_HELP,
        VersionlessSubcommands => Flags::VERSIONLESS_SC,
        WaitOnError => Flags::WAIT_ON_ERROR,
        TrailingValues => Flags::TRAILING_VALUES,
        ValidNegNumFound => Flags::VALID_NEG_NUM_FOUND,
        Propagated => Flags::PROPAGATED,
        ValidArgFound => Flags::VALID_ARG_FOUND,
        InferSubcommands => Flags::INFER_SUBCOMMANDS,
        ContainsLast => Flags::CONTAINS_LAST
    }
}

/// Application level settings, which affect how [`App`] operates
///
/// **NOTE:** When these settings are used, they apply only to current command, and are *not*
/// propagated down or up through child or parent subcommands
///
/// [`App`]: ./struct.App.html
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum AppSettings {
    /// Specifies that any invalid UTF-8 code points should *not* be treated as an error.
    /// This is the default behavior of `clap`.
    ///
    /// **NOTE:** Using argument values with invalid UTF-8 code points requires using
    /// [`ArgMatches::os_value_of`], [`ArgMatches::os_values_of`], [`ArgMatches::lossy_value_of`],
    /// or [`ArgMatches::lossy_values_of`] for those particular arguments which may contain invalid
    /// UTF-8 values
    ///
    /// **NOTE:** This rule only applies to  argument values, as flags, options, and
    /// [`SubCommand`]s themselves only allow valid UTF-8 code points.
    ///
    /// # Platform Specific
    ///
    /// Non Windows systems only
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, AppSettings};
    /// use std::ffi::OsString;
    /// use std::os::unix::ffi::{OsStrExt,OsStringExt};
    ///
    /// let r = App::new("myprog")
    ///   //.setting(AppSettings::AllowInvalidUtf8)
    ///     .arg_from_usage("<arg> 'some positional arg'")
    ///     .get_matches_from_safe(
    ///         vec![
    ///             OsString::from("myprog"),
    ///             OsString::from_vec(vec![0xe9])]);
    ///
    /// assert!(r.is_ok());
    /// let m = r.unwrap();
    /// assert_eq!(m.value_of_os("arg").unwrap().as_bytes(), &[0xe9]);
    /// ```
    /// [`ArgMatches::os_value_of`]: ./struct.ArgMatches.html#method.os_value_of
    /// [`ArgMatches::os_values_of`]: ./struct.ArgMatches.html#method.os_values_of
    /// [`ArgMatches::lossy_value_of`]: ./struct.ArgMatches.html#method.lossy_value_of
    /// [`ArgMatches::lossy_values_of`]: ./struct.ArgMatches.html#method.lossy_values_of
    /// [`SubCommand`]: ./struct.SubCommand.html
    AllowInvalidUtf8,

    /// Essentially sets [`Arg::overrides_with("itself")`] for all arguments.
    ///
    /// **WARNING:** Positional arguments cannot override themselves (or we would never be able
    /// to advance to the next positional). This setting ignores positional arguments.
    /// [`Arg::overrides_with("itself")`]: ./struct.Arg.html#method.overrides_with
    AllArgsOverrideSelf,

    /// Specifies that leading hyphens are allowed in argument *values*, such as negative numbers
    /// like `-10`. (which would otherwise be parsed as another flag or option)
    ///
    /// **NOTE:** Use this setting with caution as it silences certain circumstances which would
    /// otherwise be an error (such as accidentally forgetting to specify a value for leading
    /// option). It is preferred to set this on a per argument basis, via [`Arg::allow_hyphen_values`]
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{Arg, App, AppSettings};
    /// // Imagine you needed to represent negative numbers as well, such as -10
    /// let m = App::new("nums")
    ///     .setting(AppSettings::AllowLeadingHyphen)
    ///     .arg(Arg::with_name("neg").index(1))
    ///     .get_matches_from(vec![
    ///         "nums", "-20"
    ///     ]);
    ///
    /// assert_eq!(m.value_of("neg"), Some("-20"));
    /// # ;
    /// ```
    /// [`Arg::allow_hyphen_values`]: ./struct.Arg.html#method.allow_hyphen_values
    AllowLeadingHyphen,

    /// Allows negative numbers to pass as values. This is similar to
    /// `AllowLeadingHyphen` except that it only allows numbers, all
    /// other undefined leading hyphens will fail to parse.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// let res = App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::AllowNegativeNumbers)
    ///     .arg(Arg::with_name("num"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "-20"
    ///     ]);
    /// assert!(res.is_ok());
    /// let m = res.unwrap();
    /// assert_eq!(m.value_of("num").unwrap(), "-20");
    /// ```
    /// [`AllowLeadingHyphen`]: ./enum.AppSettings.html#variant.AllowLeadingHyphen
    AllowNegativeNumbers,

    /// Allows one to implement two styles of CLIs where positionals can be used out of order.
    ///
    /// The first example is a CLI where the second to last positional argument is optional, but
    /// the final positional argument is required. Such as `$ prog [optional] <required>` where one
    /// of the two following usages is allowed:
    ///
    /// * `$ prog [optional] <required>`
    /// * `$ prog <required>`
    ///
    /// This would otherwise not be allowed. This is useful when `[optional]` has a default value.
    ///
    /// **Note:** when using this style of "missing positionals" the final positional *must* be
    /// [required] if `--` will not be used to skip to the final positional argument.
    ///
    /// **Note:** This style also only allows a single positional argument to be "skipped" without
    /// the use of `--`. To skip more than one, see the second example.
    ///
    /// The second example is when one wants to skip multiple optional positional arguments, and use
    /// of the `--` operator is OK (but not required if all arguments will be specified anyways).
    ///
    /// For example, imagine a CLI which has three positional arguments `[foo] [bar] [baz]...` where
    /// `baz` accepts multiple values (similar to man `ARGS...` style training arguments).
    ///
    /// With this setting the following invocations are possible:
    ///
    /// * `$ prog foo bar baz1 baz2 baz3`
    /// * `$ prog foo -- baz1 baz2 baz3`
    /// * `$ prog -- baz1 baz2 baz3`
    ///
    /// # Examples
    ///
    /// Style number one from above:
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::AllowMissingPositional)
    ///     .arg(Arg::with_name("arg1"))
    ///     .arg(Arg::with_name("arg2")
    ///         .required(true))
    ///     .get_matches_from(vec![
    ///         "prog", "other"
    ///     ]);
    ///
    /// assert_eq!(m.value_of("arg1"), None);
    /// assert_eq!(m.value_of("arg2"), Some("other"));
    /// ```
    ///
    /// Now the same example, but using a default value for the first optional positional argument
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::AllowMissingPositional)
    ///     .arg(Arg::with_name("arg1")
    ///         .default_value("something"))
    ///     .arg(Arg::with_name("arg2")
    ///         .required(true))
    ///     .get_matches_from(vec![
    ///         "prog", "other"
    ///     ]);
    ///
    /// assert_eq!(m.value_of("arg1"), Some("something"));
    /// assert_eq!(m.value_of("arg2"), Some("other"));
    /// ```
    /// Style number two from above:
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::AllowMissingPositional)
    ///     .arg(Arg::with_name("foo"))
    ///     .arg(Arg::with_name("bar"))
    ///     .arg(Arg::with_name("baz").multiple(true))
    ///     .get_matches_from(vec![
    ///         "prog", "foo", "bar", "baz1", "baz2", "baz3"
    ///     ]);
    ///
    /// assert_eq!(m.value_of("foo"), Some("foo"));
    /// assert_eq!(m.value_of("bar"), Some("bar"));
    /// assert_eq!(m.values_of("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);
    /// ```
    ///
    /// Now notice if we don't specify `foo` or `baz` but use the `--` operator.
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::AllowMissingPositional)
    ///     .arg(Arg::with_name("foo"))
    ///     .arg(Arg::with_name("bar"))
    ///     .arg(Arg::with_name("baz").multiple(true))
    ///     .get_matches_from(vec![
    ///         "prog", "--", "baz1", "baz2", "baz3"
    ///     ]);
    ///
    /// assert_eq!(m.value_of("foo"), None);
    /// assert_eq!(m.value_of("bar"), None);
    /// assert_eq!(m.values_of("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);
    /// ```
    /// [required]: ./struct.Arg.html#method.required
    AllowMissingPositional,

    /// Specifies that an unexpected positional argument,
    /// which would otherwise cause a [`ErrorKind::UnknownArgument`] error,
    /// should instead be treated as a [`SubCommand`] within the [`ArgMatches`] struct.
    ///
    /// **NOTE:** Use this setting with caution,
    /// as a truly unexpected argument (i.e. one that is *NOT* an external subcommand)
    /// will **not** cause an error and instead be treated as a potential subcommand.
    /// One should check for such cases manually and inform the user appropriately.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::AllowExternalSubcommands)
    ///     .get_matches_from(vec![
    ///         "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ///     ]);
    ///
    /// // All trailing arguments will be stored under the subcommand's sub-matches using an empty
    /// // string argument name
    /// match m.subcommand() {
    ///     (external, Some(ext_m)) => {
    ///          let ext_args: Vec<&str> = ext_m.values_of("").unwrap().collect();
    ///          assert_eq!(external, "subcmd");
    ///          assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    ///     },
    ///     _ => {},
    /// }
    /// ```
    /// [`ErrorKind::UnknownArgument`]: ./enum.ErrorKind.html#variant.UnknownArgument
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    AllowExternalSubcommands,

    /// Specifies that use of a valid [argument] negates [subcommands] being used after. By default
    /// `clap` allows arguments between subcommands such as
    /// `<cmd> [cmd_args] <cmd2> [cmd2_args] <cmd3> [cmd3_args]`. This setting disables that
    /// functionality and says that arguments can only follow the *final* subcommand. For instance
    /// using this setting makes only the following invocations possible:
    ///
    /// * `<cmd> <cmd2> <cmd3> [cmd3_args]`
    /// * `<cmd> <cmd2> [cmd2_args]`
    /// * `<cmd> [cmd_args]`
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ArgsNegateSubcommands)
    /// # ;
    /// ```
    /// [subcommands]: ./struct.SubCommand.html
    /// [argument]: ./struct.Arg.html
    ArgsNegateSubcommands,

    /// Specifies that the help text should be displayed (and then exit gracefully),
    /// if no arguments are present at runtime (i.e. an empty run such as, `$ myprog`.
    ///
    /// **NOTE:** [`SubCommand`]s count as arguments
    ///
    /// **NOTE:** Setting [`Arg::default_value`] effectively disables this option as it will
    /// ensure that some argument is always present.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ArgRequiredElseHelp)
    /// # ;
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`Arg::default_value`]: ./struct.Arg.html#method.default_value
    ArgRequiredElseHelp,

    /// Uses colorized help messages.
    ///
    /// **NOTE:** Must be compiled with the `color` cargo feature
    ///
    /// # Platform Specific
    ///
    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms)
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ColoredHelp)
    ///     .get_matches();
    /// ```
    ColoredHelp,

    /// Enables colored output only when the output is going to a terminal or TTY.
    ///
    /// **NOTE:** This is the default behavior of `clap`.
    ///
    /// **NOTE:** Must be compiled with the `color` cargo feature.
    ///
    /// # Platform Specific
    ///
    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms).
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ColorAuto)
    ///     .get_matches();
    /// ```
    ColorAuto,

    /// Enables colored output regardless of whether or not the output is going to a terminal/TTY.
    ///
    /// **NOTE:** Must be compiled with the `color` cargo feature.
    ///
    /// # Platform Specific
    ///
    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms).
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ColorAlways)
    ///     .get_matches();
    /// ```
    ColorAlways,

    /// Disables colored output no matter if the output is going to a terminal/TTY, or not.
    ///
    /// **NOTE:** Must be compiled with the `color` cargo feature
    ///
    /// # Platform Specific
    ///
    /// This setting only applies to Unix, Linux, and macOS (i.e. non-Windows platforms)
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::ColorNever)
    ///     .get_matches();
    /// ```
    ColorNever,

    /// Disables the automatic collapsing of positional args into `[ARGS]` inside the usage string
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::DontCollapseArgsInUsage)
    ///     .get_matches();
    /// ```
    DontCollapseArgsInUsage,

    /// Disables the automatic delimiting of values when `--` or [`AppSettings::TrailingVarArg`]
    /// was used.
    ///
    /// **NOTE:** The same thing can be done manually by setting the final positional argument to
    /// [`Arg::use_delimiter(false)`]. Using this setting is safer, because it's easier to locate
    /// when making changes.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::DontDelimitTrailingValues)
    ///     .get_matches();
    /// ```
    /// [`AppSettings::TrailingVarArg`]: ./enum.AppSettings.html#variant.TrailingVarArg
    /// [`Arg::use_delimiter(false)`]: ./struct.Arg.html#method.use_delimiter
    DontDelimitTrailingValues,

    /// Disables `-h` and `--help` [`App`] without affecting any of the [`SubCommand`]s
    /// (Defaults to `false`; application *does* have help flags)
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings, ErrorKind};
    /// let res = App::new("myprog")
    ///     .setting(AppSettings::DisableHelpFlags)
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "-h"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);
    /// ```
    ///
    /// ```rust
    /// # use clap::{App, SubCommand, AppSettings, ErrorKind};
    /// let res = App::new("myprog")
    ///     .setting(AppSettings::DisableHelpFlags)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "test", "-h"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::HelpDisplayed);
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`App`]: ./struct.App.html
    DisableHelpFlags,

    /// Disables the `help` subcommand
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings, ErrorKind, SubCommand};
    /// let res = App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::DisableHelpSubcommand)
    ///     // Normally, creating a subcommand causes a `help` subcommand to automatically
    ///     // be generated as well
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "help"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    DisableHelpSubcommand,

    /// Disables `-V` and `--version` [`App`] without affecting any of the [`SubCommand`]s
    /// (Defaults to `false`; application *does* have a version flag)
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings, ErrorKind};
    /// let res = App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::DisableVersion)
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "-V"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);
    /// ```
    ///
    /// ```rust
    /// # use clap::{App, SubCommand, AppSettings, ErrorKind};
    /// let res = App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::DisableVersion)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "test", "-V"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::VersionDisplayed);
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`App`]: ./struct.App.html
    DisableVersion,

    /// Displays the arguments and [`SubCommand`]s in the help message in the order that they were
    /// declared in, and not alphabetically which is the default.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::DeriveDisplayOrder)
    ///     .get_matches();
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    DeriveDisplayOrder,

    /// Specifies to use the version of the current command for all child [`SubCommand`]s.
    /// (Defaults to `false`; subcommands have independent version strings from their parents.)
    ///
    /// **NOTE:** The version for the current command **and** this setting must be set **prior** to
    /// adding any child subcommands
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::GlobalVersion)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches();
    /// // running `$ myprog test --version` will display
    /// // "myprog-test v1.1"
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    GlobalVersion,

    /// Specifies that this [`SubCommand`] should be hidden from help messages
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, SubCommand};
    /// App::new("myprog")
    ///     .subcommand(SubCommand::with_name("test")
    ///     .setting(AppSettings::Hidden))
    /// # ;
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    Hidden,

    /// Tells `clap` *not* to print possible values when displaying help information.
    /// This can be useful if there are many values, or they are explained elsewhere.
    HidePossibleValuesInHelp,

    /// Tries to match unknown args to partial [`subcommands`] or their [aliases]. For example to
    /// match a subcommand named `test`, one could use `t`, `te`, `tes`, and `test`.
    ///
    /// **NOTE:** The match *must not* be ambiguous at all in order to succeed. i.e. to match `te`
    /// to `test` there could not also be a subcommand or alias `temp` because both start with `te`
    ///
    /// **CAUTION:** This setting can interfere with [positional/free arguments], take care when
    /// designing CLIs which allow inferred subcommands and have potential positional/free
    /// arguments whose values could start with the same characters as subcommands. If this is the
    /// case, it's recommended to use settings such as [`AppSeettings::ArgsNegateSubcommands`] in
    /// conjunction with this setting.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// let m = App::new("prog")
    ///     .setting(AppSettings::InferSubcommands)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from(vec![
    ///         "prog", "te"
    ///     ]);
    /// assert_eq!(m.subcommand_name(), Some("test"));
    /// ```
    /// [`subcommands`]: ./struct.SubCommand.html
    /// [positional/free arguments]: ./struct.Arg.html#method.index
    /// [aliases]: ./struct.App.html#method.alias
    /// [`AppSeettings::ArgsNegateSubcommands`]: ./enum.AppSettings.html#variant.ArgsNegateSubcommands
    InferSubcommands,

    /// Specifies that the parser should not assume the first argument passed is the binary name.
    /// This is normally the case when using a "daemon" style mode, or an interactive CLI where one
    /// one would not normally type the binary or program name for each command.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::NoBinaryName)
    ///     .arg(Arg::from_usage("<cmd>... 'commands to run'"))
    ///     .get_matches_from(vec!["command", "set"]);
    ///
    /// let cmds: Vec<&str> = m.values_of("cmd").unwrap().collect();
    /// assert_eq!(cmds, ["command", "set"]);
    /// ```
    NoBinaryName,

    /// Places the help string for all arguments on the line after the argument.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::NextLineHelp)
    ///     .get_matches();
    /// ```
    NextLineHelp,

    /// **DEPRECATED**: This setting is no longer required in order to propagate values up or down
    ///
    /// Specifies that the parser should propagate global arg's values down or up through any *used*
    /// child subcommands. Meaning, if a subcommand wasn't used, the values won't be propagated to
    /// said subcommand.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, SubCommand};
    /// let m = App::new("myprog")
    ///     .arg(Arg::from_usage("[cmd] 'command to run'")
    ///         .global(true))
    ///     .subcommand(SubCommand::with_name("foo"))
    ///     .get_matches_from(vec!["myprog", "set", "foo"]);
    ///
    /// assert_eq!(m.value_of("cmd"), Some("set"));
    ///
    /// let sub_m = m.subcommand_matches("foo").unwrap();
    /// assert_eq!(sub_m.value_of("cmd"), Some("set"));
    /// ```
    /// Now doing the same thing, but *not* using any subcommands will result in the value not being
    /// propagated down.
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, SubCommand};
    /// let m = App::new("myprog")
    ///     .arg(Arg::from_usage("[cmd] 'command to run'")
    ///         .global(true))
    ///     .subcommand(SubCommand::with_name("foo"))
    ///     .get_matches_from(vec!["myprog", "set"]);
    ///
    /// assert_eq!(m.value_of("cmd"), Some("set"));
    ///
    /// assert!(m.subcommand_matches("foo").is_none());
    /// ```
    #[deprecated(since = "2.27.0", note = "No longer required to propagate values")]
    PropagateGlobalValuesDown,

    /// Allows [`SubCommand`]s to override all requirements of the parent command.
    /// For example if you had a subcommand or top level application with a required argument
    /// that is only required as long as there is no subcommand present,
    /// using this setting would allow you to set those arguments to [`Arg::required(true)`]
    /// and yet receive no error so long as the user uses a valid subcommand instead.
    ///
    /// **NOTE:** This defaults to false (using subcommand does *not* negate requirements)
    ///
    /// # Examples
    ///
    /// This first example shows that it is an error to not use a required argument
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, SubCommand, ErrorKind};
    /// let err = App::new("myprog")
    ///     .setting(AppSettings::SubcommandsNegateReqs)
    ///     .arg(Arg::with_name("opt").required(true))
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog"
    ///     ]);
    /// assert!(err.is_err());
    /// assert_eq!(err.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
    /// # ;
    /// ```
    ///
    /// This next example shows that it is no longer error to not use a required argument if a
    /// valid subcommand is used.
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings, SubCommand, ErrorKind};
    /// let noerr = App::new("myprog")
    ///     .setting(AppSettings::SubcommandsNegateReqs)
    ///     .arg(Arg::with_name("opt").required(true))
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "test"
    ///     ]);
    /// assert!(noerr.is_ok());
    /// # ;
    /// ```
    /// [`Arg::required(true)`]: ./struct.Arg.html#method.required
    /// [`SubCommand`]: ./struct.SubCommand.html
    SubcommandsNegateReqs,

    /// Specifies that the help text should be displayed (before exiting gracefully) if no
    /// [`SubCommand`]s are present at runtime (i.e. an empty run such as `$ myprog`).
    ///
    /// **NOTE:** This should *not* be used with [`AppSettings::SubcommandRequired`] as they do
    /// nearly same thing; this prints the help text, and the other prints an error.
    ///
    /// **NOTE:** If the user specifies arguments at runtime, but no subcommand the help text will
    /// still be displayed and exit. If this is *not* the desired result, consider using
    /// [`AppSettings::ArgRequiredElseHelp`] instead.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::SubcommandRequiredElseHelp)
    /// # ;
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`AppSettings::SubcommandRequired`]: ./enum.AppSettings.html#variant.SubcommandRequired
    /// [`AppSettings::ArgRequiredElseHelp`]: ./enum.AppSettings.html#variant.ArgRequiredElseHelp
    SubcommandRequiredElseHelp,

    /// Specifies that any invalid UTF-8 code points should be treated as an error and fail
    /// with a [`ErrorKind::InvalidUtf8`] error.
    ///
    /// **NOTE:** This rule only applies to argument values; Things such as flags, options, and
    /// [`SubCommand`]s themselves only allow valid UTF-8 code points.
    ///
    /// # Platform Specific
    ///
    /// Non Windows systems only
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, AppSettings, ErrorKind};
    /// use std::ffi::OsString;
    /// use std::os::unix::ffi::OsStringExt;
    ///
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::StrictUtf8)
    ///     .arg_from_usage("<arg> 'some positional arg'")
    ///     .get_matches_from_safe(
    ///         vec![
    ///             OsString::from("myprog"),
    ///             OsString::from_vec(vec![0xe9])]);
    ///
    /// assert!(m.is_err());
    /// assert_eq!(m.unwrap_err().kind, ErrorKind::InvalidUtf8);
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    /// [`ErrorKind::InvalidUtf8`]: ./enum.ErrorKind.html#variant.InvalidUtf8
    StrictUtf8,

    /// Allows specifying that if no [`SubCommand`] is present at runtime,
    /// error and exit gracefully.
    ///
    /// **NOTE:** This defaults to `false` (subcommands do *not* need to be present)
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, AppSettings, SubCommand, ErrorKind};
    /// let err = App::new("myprog")
    ///     .setting(AppSettings::SubcommandRequired)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog",
    ///     ]);
    /// assert!(err.is_err());
    /// assert_eq!(err.unwrap_err().kind, ErrorKind::MissingSubcommand);
    /// # ;
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    SubcommandRequired,

    /// Specifies that the final positional argument is a "VarArg" and that `clap` should not
    /// attempt to parse any further args.
    ///
    /// The values of the trailing positional argument will contain all args from itself on.
    ///
    /// **NOTE:** The final positional argument **must** have [`Arg::multiple(true)`] or the usage
    /// string equivalent.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// let m = App::new("myprog")
    ///     .setting(AppSettings::TrailingVarArg)
    ///     .arg(Arg::from_usage("<cmd>... 'commands to run'"))
    ///     .get_matches_from(vec!["myprog", "arg1", "-r", "val1"]);
    ///
    /// let trail: Vec<&str> = m.values_of("cmd").unwrap().collect();
    /// assert_eq!(trail, ["arg1", "-r", "val1"]);
    /// ```
    /// [`Arg::multiple(true)`]: ./struct.Arg.html#method.multiple
    TrailingVarArg,

    /// Groups flags and options together, presenting a more unified help message
    /// (a la `getopts` or `docopt` style).
    ///
    /// The default is that the auto-generated help message will group flags, and options
    /// separately.
    ///
    /// **NOTE:** This setting is cosmetic only and does not affect any functionality.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::UnifiedHelpMessage)
    ///     .get_matches();
    /// // running `myprog --help` will display a unified "docopt" or "getopts" style help message
    /// ```
    UnifiedHelpMessage,

    /// Disables `-V` and `--version` for all [`SubCommand`]s
    /// (Defaults to `false`; subcommands *do* have version flags.)
    ///
    /// **NOTE:** This setting must be set **prior** to adding any subcommands.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, SubCommand, AppSettings, ErrorKind};
    /// let res = App::new("myprog")
    ///     .version("v1.1")
    ///     .setting(AppSettings::VersionlessSubcommands)
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches_from_safe(vec![
    ///         "myprog", "test", "-V"
    ///     ]);
    /// assert!(res.is_err());
    /// assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    VersionlessSubcommands,

    /// Will display a message "Press \[ENTER\]/\[RETURN\] to continue..." and wait for user before
    /// exiting
    ///
    /// This is most useful when writing an application which is run from a GUI shortcut, or on
    /// Windows where a user tries to open the binary by double-clicking instead of using the
    /// command line.
    ///
    /// **NOTE:** This setting is **not** recursive with [`SubCommand`]s, meaning if you wish this
    /// behavior for all subcommands, you must set this on each command (needing this is extremely
    /// rare)
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, AppSettings};
    /// App::new("myprog")
    ///     .setting(AppSettings::WaitOnError)
    /// # ;
    /// ```
    /// [`SubCommand`]: ./struct.SubCommand.html
    WaitOnError,

    #[doc(hidden)]
    NeedsLongVersion,

    #[doc(hidden)]
    NeedsLongHelp,

    #[doc(hidden)]
    NeedsSubcommandHelp,

    #[doc(hidden)]
    LowIndexMultiplePositional,

    #[doc(hidden)]
    TrailingValues,

    #[doc(hidden)]
    ValidNegNumFound,

    #[doc(hidden)]
    Propagated,

    #[doc(hidden)]
    ValidArgFound,

    #[doc(hidden)]
    ContainsLast,
}

impl FromStr for AppSettings {
    type Err = String;
    fn from_str(s: &str) -> Result<Self, <Self as FromStr>::Err> {
        match &*s.to_ascii_lowercase() {
            "disablehelpflags" => Ok(AppSettings::DisableHelpFlags),
            "argrequiredelsehelp" => Ok(AppSettings::ArgRequiredElseHelp),
            "argsnegatesubcommands" => Ok(AppSettings::ArgsNegateSubcommands),
            "allowinvalidutf8" => Ok(AppSettings::AllowInvalidUtf8),
            "allowleadinghyphen" => Ok(AppSettings::AllowLeadingHyphen),
            "allowexternalsubcommands" => Ok(AppSettings::AllowExternalSubcommands),
            "allownegativenumbers" => Ok(AppSettings::AllowNegativeNumbers),
            "colorauto" => Ok(AppSettings::ColorAuto),
            "coloralways" => Ok(AppSettings::ColorAlways),
            "colornever" => Ok(AppSettings::ColorNever),
            "coloredhelp" => Ok(AppSettings::ColoredHelp),
            "derivedisplayorder" => Ok(AppSettings::DeriveDisplayOrder),
            "dontcollapseargsinusage" => Ok(AppSettings::DontCollapseArgsInUsage),
            "dontdelimittrailingvalues" => Ok(AppSettings::DontDelimitTrailingValues),
            "disablehelpsubcommand" => Ok(AppSettings::DisableHelpSubcommand),
            "disableversion" => Ok(AppSettings::DisableVersion),
            "globalversion" => Ok(AppSettings::GlobalVersion),
            "hidden" => Ok(AppSettings::Hidden),
            "hidepossiblevaluesinhelp" => Ok(AppSettings::HidePossibleValuesInHelp),
            "infersubcommands" => Ok(AppSettings::InferSubcommands),
            "lowindexmultiplepositional" => Ok(AppSettings::LowIndexMultiplePositional),
            "nobinaryname" => Ok(AppSettings::NoBinaryName),
            "nextlinehelp" => Ok(AppSettings::NextLineHelp),
            "strictutf8" => Ok(AppSettings::StrictUtf8),
            "subcommandsnegatereqs" => Ok(AppSettings::SubcommandsNegateReqs),
            "subcommandrequired" => Ok(AppSettings::SubcommandRequired),
            "subcommandrequiredelsehelp" => Ok(AppSettings::SubcommandRequiredElseHelp),
            "trailingvararg" => Ok(AppSettings::TrailingVarArg),
            "unifiedhelpmessage" => Ok(AppSettings::UnifiedHelpMessage),
            "versionlesssubcommands" => Ok(AppSettings::VersionlessSubcommands),
            "waitonerror" => Ok(AppSettings::WaitOnError),
            "validnegnumfound" => Ok(AppSettings::ValidNegNumFound),
            "validargfound" => Ok(AppSettings::ValidArgFound),
            "propagated" => Ok(AppSettings::Propagated),
            "trailingvalues" => Ok(AppSettings::TrailingValues),
            _ => Err("unknown AppSetting, cannot convert from str".to_owned()),
        }
    }
}

#[cfg(test)]
mod test {
    use super::AppSettings;

    #[test]
    fn app_settings_fromstr() {
        assert_eq!(
            "disablehelpflags".parse::<AppSettings>().unwrap(),
            AppSettings::DisableHelpFlags
        );
        assert_eq!(
            "argsnegatesubcommands".parse::<AppSettings>().unwrap(),
            AppSettings::ArgsNegateSubcommands
        );
        assert_eq!(
            "argrequiredelsehelp".parse::<AppSettings>().unwrap(),
            AppSettings::ArgRequiredElseHelp
        );
        assert_eq!(
            "allowexternalsubcommands".parse::<AppSettings>().unwrap(),
            AppSettings::AllowExternalSubcommands
        );
        assert_eq!(
            "allowinvalidutf8".parse::<AppSettings>().unwrap(),
            AppSettings::AllowInvalidUtf8
        );
        assert_eq!(
            "allowleadinghyphen".parse::<AppSettings>().unwrap(),
            AppSettings::AllowLeadingHyphen
        );
        assert_eq!(
            "allownegativenumbers".parse::<AppSettings>().unwrap(),
            AppSettings::AllowNegativeNumbers
        );
        assert_eq!(
            "coloredhelp".parse::<AppSettings>().unwrap(),
            AppSettings::ColoredHelp
        );
        assert_eq!(
            "colorauto".parse::<AppSettings>().unwrap(),
            AppSettings::ColorAuto
        );
        assert_eq!(
            "coloralways".parse::<AppSettings>().unwrap(),
            AppSettings::ColorAlways
        );
        assert_eq!(
            "colornever".parse::<AppSettings>().unwrap(),
            AppSettings::ColorNever
        );
        assert_eq!(
            "disablehelpsubcommand".parse::<AppSettings>().unwrap(),
            AppSettings::DisableHelpSubcommand
        );
        assert_eq!(
            "disableversion".parse::<AppSettings>().unwrap(),
            AppSettings::DisableVersion
        );
        assert_eq!(
            "dontcollapseargsinusage".parse::<AppSettings>().unwrap(),
            AppSettings::DontCollapseArgsInUsage
        );
        assert_eq!(
            "dontdelimittrailingvalues".parse::<AppSettings>().unwrap(),
            AppSettings::DontDelimitTrailingValues
        );
        assert_eq!(
            "derivedisplayorder".parse::<AppSettings>().unwrap(),
            AppSettings::DeriveDisplayOrder
        );
        assert_eq!(
            "globalversion".parse::<AppSettings>().unwrap(),
            AppSettings::GlobalVersion
        );
        assert_eq!(
            "hidden".parse::<AppSettings>().unwrap(),
            AppSettings::Hidden
        );
        assert_eq!(
            "hidepossiblevaluesinhelp".parse::<AppSettings>().unwrap(),
            AppSettings::HidePossibleValuesInHelp
        );
        assert_eq!(
            "lowindexmultiplePositional".parse::<AppSettings>().unwrap(),
            AppSettings::LowIndexMultiplePositional
        );
        assert_eq!(
            "nobinaryname".parse::<AppSettings>().unwrap(),
            AppSettings::NoBinaryName
        );
        assert_eq!(
            "nextlinehelp".parse::<AppSettings>().unwrap(),
            AppSettings::NextLineHelp
        );
        assert_eq!(
            "subcommandsnegatereqs".parse::<AppSettings>().unwrap(),
            AppSettings::SubcommandsNegateReqs
        );
        assert_eq!(
            "subcommandrequired".parse::<AppSettings>().unwrap(),
            AppSettings::SubcommandRequired
        );
        assert_eq!(
            "subcommandrequiredelsehelp".parse::<AppSettings>().unwrap(),
            AppSettings::SubcommandRequiredElseHelp
        );
        assert_eq!(
            "strictutf8".parse::<AppSettings>().unwrap(),
            AppSettings::StrictUtf8
        );
        assert_eq!(
            "trailingvararg".parse::<AppSettings>().unwrap(),
            AppSettings::TrailingVarArg
        );
        assert_eq!(
            "unifiedhelpmessage".parse::<AppSettings>().unwrap(),
            AppSettings::UnifiedHelpMessage
        );
        assert_eq!(
            "versionlesssubcommands".parse::<AppSettings>().unwrap(),
            AppSettings::VersionlessSubcommands
        );
        assert_eq!(
            "waitonerror".parse::<AppSettings>().unwrap(),
            AppSettings::WaitOnError
        );
        assert_eq!(
            "validnegnumfound".parse::<AppSettings>().unwrap(),
            AppSettings::ValidNegNumFound
        );
        assert_eq!(
            "validargfound".parse::<AppSettings>().unwrap(),
            AppSettings::ValidArgFound
        );
        assert_eq!(
            "propagated".parse::<AppSettings>().unwrap(),
            AppSettings::Propagated
        );
        assert_eq!(
            "trailingvalues".parse::<AppSettings>().unwrap(),
            AppSettings::TrailingValues
        );
        assert_eq!(
            "infersubcommands".parse::<AppSettings>().unwrap(),
            AppSettings::InferSubcommands
        );
        assert!("hahahaha".parse::<AppSettings>().is_err());
    }
}