argp 0.4.0

// SPDX-License-Identifier: BSD-3-Clause
// SPDX-FileCopyrightText: 2023 Jakub Jirutka <jakub@jirutka.cz>
// SPDX-FileCopyrightText: 2020 Google LLC

//! Derive-based argument parsing optimized for code size and flexibility.
//!
//! The public API of this library consists primarily of the [`FromArgs`] derive
//! and the [`parse_args_or_exit`] function, which can be used to produce a
//! top-level [`FromArgs`] type from the current program's command-line
//! arguments.
//!
//! ## Basic Example
//!
//! ```rust,no_run
//! use argp::FromArgs;
//!
//! /// Reach new heights.
//! #[derive(FromArgs)]
//! struct GoUp {
//!     /// Whether or not to jump.
//!     #[argp(switch, short = 'j')]
//!     jump: bool,
//!
//!     /// How high to go.
//!     #[argp(option)]
//!     height: usize,
//!
//!     /// An optional nickname for the pilot.
//!     #[argp(option)]
//!     pilot_nickname: Option<String>,
//! }
//!
//! let up: GoUp = argp::parse_args_or_exit(argp::DEFAULT);
//! ```
//!
//! `./some_bin --help` will then output the following:
//!
//! ```bash
//! Usage: cmdname [-j] --height <height> [--pilot-nickname <pilot-nickname>]
//!
//! Reach new heights.
//!
//! Options:
//!   -j, --jump        Whether or not to jump.
//!   --height          How high to go.
//!   --pilot-nickname  An optional nickname for the pilot.
//!   --help            Show this help message and exit.
//! ```
//!
//! The resulting program can then be used in any of these ways:
//! - `./some_bin --height 5`
//! - `./some_bin -j --height 5`
//! - `./some_bin --jump --height 5 --pilot-nickname Wes`
//!
//! Switches, like `jump`, are optional and will be set to true if provided.
//!
//! Options, like `height` and `pilot_nickname`, can be either required,
//! optional, or repeating, depending on whether they are contained in an
//! `Option` or a `Vec`. Default values can be provided using the
//! `#[argp(default = "<your_code_here>")]` attribute, and in this case an
//! option is treated as optional.
//!
//! ```rust
//! use argp::FromArgs;
//!
//! fn default_height() -> usize {
//!     5
//! }
//!
//! /// Reach new heights.
//! #[derive(FromArgs)]
//! struct GoUp {
//!     /// An optional nickname for the pilot.
//!     #[argp(option)]
//!     pilot_nickname: Option<String>,
//!
//!     /// An optional height.
//!     #[argp(option, default = "default_height()")]
//!     height: usize,
//!
//!     /// An optional direction which is "up" by default.
//!     #[argp(option, default = "String::from(\"only up\")")]
//!     direction: String,
//! }
//!
//! fn main() {
//!     let up: GoUp = argp::parse_args_or_exit(argp::DEFAULT);
//! }
//! ```
//!
//! Custom option types can be deserialized so long as they implement the
//! [`FromArgValue`] trait (already implemented for most types in std for which
//! the `FromStr` trait is implemented). If more customized parsing is required,
//! you can supply a custom `fn(&str) -> Result<T, E>` using the `from_str_fn`
//! attribute, or `fn(&OsStr) -> Result<T, E>` using the `from_os_str_fn`
//! attribute, where `E` implements `ToString`:
//!
//! ```
//! # use argp::FromArgs;
//! # use std::ffi::OsStr;
//! # use std::path::PathBuf;
//!
//! /// Goofy thing.
//! #[derive(FromArgs)]
//! struct FineStruct {
//!     /// Always five.
//!     #[argp(option, from_str_fn(always_five))]
//!     five: usize,
//!
//!     /// File path.
//!     #[argp(option, from_os_str_fn(convert_path))]
//!     path: PathBuf,
//! }
//!
//! fn always_five(_value: &str) -> Result<usize, String> {
//!     Ok(5)
//! }
//!
//! fn convert_path(value: &OsStr) -> Result<PathBuf, String> {
//!     Ok(PathBuf::from("/tmp").join(value))
//! }
//! ```
//!
//! Positional arguments can be declared using `#[argp(positional)]`. These
//! arguments will be parsed in order of their declaration in the structure:
//!
//! ```rust
//! # use argp::FromArgs;
//!
//! /// A command with positional arguments.
//! #[derive(FromArgs, PartialEq, Debug)]
//! struct WithPositional {
//!     #[argp(positional)]
//!     first: String,
//! }
//! ```
//!
//! The last positional argument may include a default, or be wrapped in
//! `Option` or `Vec` to indicate an optional or repeating positional argument.
//!
//! If your final positional argument has the `greedy` option on it, it will
//! consume any arguments after it as if a `--` were placed before the first
//! argument to match the greedy positional:
//!
//! ```rust
//! # use argp::FromArgs;
//!
//! /// A command with a greedy positional argument at the end.
//! #[derive(FromArgs, PartialEq, Debug)]
//! struct WithGreedyPositional {
//!     /// Some stuff.
//!     #[argp(option)]
//!     stuff: Option<String>,
//!     #[argp(positional, greedy)]
//!     all_the_rest: Vec<String>,
//! }
//! ```
//!
//! Now if you pass `--stuff Something` after a positional argument, it will be
//! consumed by `all_the_rest` instead of setting the `stuff` field.
//!
//! Note that `all_the_rest` won't be listed as a positional argument in the
//! long text part of help output (and it will be listed at the end of the usage
//! line as `[all_the_rest...]`), and it's up to the caller to append any extra
//! help output for the meaning of the captured arguments. This is to enable
//! situations where some amount of argument processing needs to happen before
//! the rest of the arguments can be interpreted, and shouldn't be used for
//! regular use as it might be confusing.
//!
//! ## Subcommands
//!
//! Subcommands are also supported. To use a subcommand, declare a separate
//! [`FromArgs`] type for each subcommand as well as an enum that cases over
//! each command:
//!
//! ```rust
//! # use argp::FromArgs;
//!
//! /// Top-level command.
//! #[derive(FromArgs, PartialEq, Debug)]
//! struct TopLevel {
//!     /// Be verbose.
//!     #[argp(switch, short = 'v', global)]
//!     verbose: bool,
//!
//!     /// Run locally.
//!     #[argp(switch)]
//!     quiet: bool,
//!
//!     #[argp(subcommand)]
//!     nested: MySubCommandEnum,
//! }
//!
//! #[derive(FromArgs, PartialEq, Debug)]
//! #[argp(subcommand)]
//! enum MySubCommandEnum {
//!     One(SubCommandOne),
//!     Two(SubCommandTwo),
//! }
//!
//! /// First subcommand.
//! #[derive(FromArgs, PartialEq, Debug)]
//! #[argp(subcommand, name = "one")]
//! struct SubCommandOne {
//!     /// How many x.
//!     #[argp(option)]
//!     x: usize,
//! }
//!
//! /// Second subcommand.
//! #[derive(FromArgs, PartialEq, Debug)]
//! #[argp(subcommand, name = "two")]
//! struct SubCommandTwo {
//!     /// Whether to fooey.
//!     #[argp(switch)]
//!     fooey: bool,
//! }
//! ```
//!
//! Normally the options specified in `TopLevel` must be placed before the
//! subcommand name, e.g. `./some_bin --quiet one --x 42` will work, but
//! `./some_bin one --quiet --x 42` won't. To allow an option from a higher
//! level to be used at a lower level (in subcommands), you can specify the
//! `global` attribute to the option (`--verbose` in the example above).
//!
//! Global options only propagate down, not up (to parent commands), but their
//! values are propagated back up to the parent once a user has used them. In
//! effect, this means that you should define all global arguments at the top
//! level, but it doesn't matter where the user uses the global argument.
//!
//! You can also discover subcommands dynamically at runtime. To do this,
//! declare subcommands as usual and add a variant to the enum with the
//! `dynamic` attribute. Instead of deriving `FromArgs`, the value inside the
//! dynamic variant should implement `DynamicSubCommand`.
//!
//! ```rust
//! # use argp::CommandInfo;
//! # use argp::DynamicSubCommand;
//! # use argp::EarlyExit;
//! # use argp::Error;
//! # use argp::FromArgs;
//! # use once_cell::sync::OnceCell;
//! # use std::ffi::OsStr;
//!
//! /// Top-level command.
//! #[derive(FromArgs, PartialEq, Debug)]
//! struct TopLevel {
//!     #[argp(subcommand)]
//!     nested: MySubCommandEnum,
//! }
//!
//! #[derive(FromArgs, PartialEq, Debug)]
//! #[argp(subcommand)]
//! enum MySubCommandEnum {
//!     Normal(NormalSubCommand),
//!     #[argp(dynamic)]
//!     Dynamic(Dynamic),
//! }
//!
//! /// Normal subcommand.
//! #[derive(FromArgs, PartialEq, Debug)]
//! #[argp(subcommand, name = "normal")]
//! struct NormalSubCommand {
//!     /// How many x.
//!     #[argp(option)]
//!     x: usize,
//! }
//!
//! /// Dynamic subcommand.
//! #[derive(PartialEq, Debug)]
//! struct Dynamic {
//!     name: String
//! }
//!
//! impl DynamicSubCommand for Dynamic {
//!     fn commands() -> &'static [&'static CommandInfo] {
//!         static RET: OnceCell<Vec<&'static CommandInfo>> = OnceCell::new();
//!         RET.get_or_init(|| {
//!             let mut commands = Vec::new();
//!
//!             // argp needs the `CommandInfo` structs we generate to be valid
//!             // for the static lifetime. We can allocate the structures on
//!             // the heap with `Box::new` and use `Box::leak` to get a static
//!             // reference to them. We could also just use a constant
//!             // reference, but only because this is a synthetic example; the
//!             // point of using dynamic commands is to have commands you
//!             // don't know about until runtime!
//!             commands.push(&*Box::leak(Box::new(CommandInfo {
//!                 name: "dynamic_command",
//!                 description: "A dynamic command",
//!             })));
//!
//!             commands
//!         })
//!     }
//!
//!     fn try_from_args(command_name: &[&str], args: &[&OsStr]) -> Option<Result<Self, EarlyExit>> {
//!         for command in Self::commands() {
//!             if command_name.last() == Some(&command.name) {
//!                 if !args.is_empty() {
//!                     return Some(Err(Error::other("Our example dynamic command never takes arguments!").into()));
//!                 }
//!                 return Some(Ok(Dynamic { name: command.name.to_string() }))
//!             }
//!         }
//!         None
//!     }
//! }
//! ```
//!
//! ## Help message
//!
//! The formatting of the help message can be customized using the [`HelpStyle`]
//! passed as an argument to [`parse_args_or_exit`]:
//!
//! ```rust
//! # use argp::{FromArgs, HelpStyle};
//! #
//! # /// A command.
//! # #[derive(FromArgs)]
//! # struct Args {
//! #     /// Be verbose.
//! #     #[argp(switch)]
//! #     verbose: bool,
//! # }
//!
//! let args: Args = argp::parse_args_or_exit(&HelpStyle {
//!     blank_lines_spacing: 1,
//!     description_indent: 8,
//!     ..HelpStyle::default()
//! });
//! ```
//!
//! Note that the [`HelpStyle`] struct may be extended with more fields in the
//! future, so always initialise it using [`HelpStyle::default()`] as shown
//! above.
//!
//! Programs that are run from an environment such as cargo may find it useful
//! to have positional arguments present in the structure but omitted from the
//! usage output. This can be accomplished by adding the `hidden_help` attribute
//! to that argument:
//!
//! ```rust
//! # use argp::FromArgs;
//!
//! /// Cargo arguments
//! #[derive(FromArgs)]
//! struct CargoArgs {
//!     // Cargo puts the command name invoked into the first argument,
//!     // so we don't want this argument to show up in the usage text.
//!     #[argp(positional, hidden_help)]
//!     command: String,
//!     /// An option used for internal debugging.
//!     #[argp(option, hidden_help)]
//!     internal_debugging: String,
//!     #[argp(positional)]
//!     real_first_arg: String,
//! }
//! ```
//!
//! ### Markdown
//!
//! Any descriptions provided as a doc comment (or `doc` attribute) are
//! interpreted as Markdown and converted to plain text (at build time) as shown
//! in the table below. The output format may change slightly in the future.
//!
//! | Markdown                                        | Output                                              |
//! |:------------------------------------------------|:----------------------------------------------------|
//! | `# Heading`, `## Heading`, ...                  | `Heading`                                           |
//! | `*italic*`, `_italic_`                          | `italic`                                            |
//! | `**bold**`, `__bold__`                          | `*bold*`                                            |
//! | `` `monospace` ``                               | `` `monospace` ``                                   |
//! | `[link title](https://example.org)`             | `https://example.org`                               |
//! | <pre>* unordered list<br>  - nested list </pre> | <pre>* unordered list<br>  * nested list     </pre> |
//! | <pre>1. ordered list<br>  1. nested list </pre> | <pre>1. ordered list<br>   1. nested list    </pre> |
//! | <pre>\```<br>code<br>block<br>\```       </pre> | <pre>code<br>block                           </pre> |
//! | <pre>> block<br>> quote<br>><br>>> nested</pre> | <pre>  block<br>  quote<br><br>    nested    </pre> |
//! | `<p>html</p>`                                   | `<p>html</p>`                                       |
//! | `Line<br>break`                                 | <pre>Line<br>break                           </pre> |
//!
//! If you want to remove an implicit blank line between two blocks, for example
//! a paragraph and a list, you can do this with `<br>`:
//!
//! ```plain
//! List of items:<br>
//! * one
//! * two
//! ```
//!
//! This can also be used to write several empty lines in a row, which would otherwise be stripped.

#![deny(missing_docs)]

mod error;
pub mod help;
pub mod parser;
pub mod term_size;

use std::borrow::Cow;
use std::env;
use std::ffi::{OsStr, OsString};
use std::fmt;
use std::path::{Path, PathBuf};
use std::process::exit;

use crate::help::{Help, HelpInfo};
use crate::parser::ParseGlobalOptions;

pub use crate::error::{Error, MissingRequirements};
pub use crate::help::{CommandInfo, HelpStyle};
pub use argp_derive::FromArgs;

/// A convenient shortcut for [`HelpStyle::default`].
pub const DEFAULT: &HelpStyle = &HelpStyle::default();

/// Types which can be constructed from a set of command-line arguments.
pub trait FromArgs: Sized {
    /// Construct the type from an input set of arguments.
    ///
    /// The first argument `command_name` is the identifier for the current
    /// command. In most cases, users should only pass in a single item for the
    /// command name, which typically comes from the first item from
    /// [`std::env::args_os()`]. Implementations however should append the
    /// subcommand name in when recursively calling [`FromArgs::from_args`] for
    /// subcommands. This allows `argp` to generate correct subcommand help
    /// strings.
    ///
    /// The second argument `args` is the rest of the command line arguments.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use argp::{EarlyExit, FromArgs};
    ///
    /// /// Command to manage a classroom.
    /// #[derive(Debug, PartialEq, FromArgs)]
    /// struct ClassroomCmd {
    ///     #[argp(subcommand)]
    ///     subcommands: Subcommands,
    /// }
    ///
    /// #[derive(Debug, PartialEq, FromArgs)]
    /// #[argp(subcommand)]
    /// enum Subcommands {
    ///     List(ListCmd),
    ///     Add(AddCmd),
    /// }
    ///
    /// /// List all the classes.
    /// #[derive(Debug, PartialEq, FromArgs)]
    /// #[argp(subcommand, name = "list")]
    /// struct ListCmd {
    ///     /// List classes for only this teacher.
    ///     #[argp(option, arg_name = "name")]
    ///     teacher_name: Option<String>,
    /// }
    ///
    /// /// Add students to a class.
    /// #[derive(Debug, PartialEq, FromArgs)]
    /// #[argp(subcommand, name = "add")]
    /// struct AddCmd {
    ///     /// The name of the class's teacher.
    ///     #[argp(option)]
    ///     teacher_name: String,
    ///
    ///     /// The name of the class.
    ///     #[argp(positional)]
    ///     class_name: String,
    /// }
    ///
    /// let args = ClassroomCmd::from_args(
    ///     &["classroom"],
    ///     &["list", "--teacher-name", "Smith"],
    /// ).unwrap();
    /// assert_eq!(
    ///    args,
    ///     ClassroomCmd {
    ///         subcommands: Subcommands::List(ListCmd {
    ///             teacher_name: Some("Smith".to_string()),
    ///         })
    ///     },
    /// );
    ///
    /// // Help returns an error with `EarlyExit::Help`.
    /// let early_exit = ClassroomCmd::from_args(
    ///     &["classroom"],
    ///     &["help"],
    /// ).unwrap_err();
    /// match early_exit {
    ///     EarlyExit::Help(help) => assert_eq!(
    ///         help.generate_default(),
    ///         r#"Usage: classroom <command> [<args>]
    ///
    /// Command to manage a classroom.
    ///
    /// Options:
    ///   -h, --help  Show this help message and exit.
    ///
    /// Commands:
    ///   list        List all the classes.
    ///   add         Add students to a class.
    /// "#.to_owned(),
    ///     ),
    ///     _ => panic!("expected help"),
    /// };
    ///
    /// // Help works with subcommands.
    /// let early_exit = ClassroomCmd::from_args(
    ///     &["classroom"],
    ///     &["list", "help"],
    /// ).unwrap_err();
    /// match early_exit {
    ///     EarlyExit::Help(help) => assert_eq!(
    ///         help.generate_default(),
    ///         r#"Usage: classroom list [--teacher-name <name>]
    ///
    /// List all the classes.
    ///
    /// Options:
    ///       --teacher-name <name>  List classes for only this teacher.
    ///   -h, --help                 Show this help message and exit.
    /// "#.to_owned(),
    ///     ),
    ///     _ => panic!("expected help"),
    /// };
    ///
    /// // Incorrect arguments will error out.
    /// let err = ClassroomCmd::from_args(
    ///     &["classroom"],
    ///     &["lisp"],
    /// ).unwrap_err();
    /// assert_eq!(
    ///    err,
    ///    argp::EarlyExit::Err(argp::Error::UnknownArgument("lisp".into())),
    /// );
    /// ```
    fn from_args<S: AsRef<OsStr>>(command_name: &[&str], args: &[S]) -> Result<Self, EarlyExit> {
        let args: Vec<_> = args.iter().map(AsRef::as_ref).collect();
        Self::_from_args(command_name, &args, None)
    }

    #[doc(hidden)]
    fn _from_args(
        command_name: &[&str],
        args: &[&OsStr],
        parent: Option<&mut dyn ParseGlobalOptions>,
    ) -> Result<Self, EarlyExit>;
}

/// A top-level [`FromArgs`] implementation that is not a subcommand.
pub trait TopLevelCommand: FromArgs {}

/// A [`FromArgs`] implementation that can parse into one or more subcommands.
pub trait SubCommands: FromArgs {
    /// Info for the commands.
    const COMMANDS: &'static [&'static CommandInfo];

    /// Get a list of commands that are discovered at runtime.
    fn dynamic_commands() -> &'static [&'static CommandInfo] {
        &[]
    }
}

/// A [`FromArgs`] implementation that represents a single subcommand.
pub trait SubCommand: FromArgs {
    /// Information about the subcommand.
    const COMMAND: &'static CommandInfo;
}

impl<T: SubCommand> SubCommands for T {
    const COMMANDS: &'static [&'static CommandInfo] = &[T::COMMAND];
}

/// Trait implemented by values returned from a dynamic subcommand handler.
pub trait DynamicSubCommand: Sized {
    /// Info about supported subcommands.
    fn commands() -> &'static [&'static CommandInfo];

    /// Perform the function of [`FromArgs::from_args`] for this dynamic
    /// command.
    ///
    /// The full list of subcommands, ending with the subcommand that should be
    /// dynamically recognized, is passed in `command_name`. If the command
    /// passed is not recognized, this function should return `None`. Otherwise
    /// it should return `Some`, and the value within the `Some` has the same
    /// semantics as the return of [`FromArgs::from_args`].
    fn try_from_args(command_name: &[&str], args: &[&OsStr]) -> Option<Result<Self, EarlyExit>>;
}

/// A [`FromArgs`] implementation with attached [`HelpInfo`] struct.
pub trait CommandHelp: FromArgs {
    /// Information for generating the help message.
    const HELP: HelpInfo;
}

/// Types which can be constructed from a single command-line value.
///
/// Any field type declared in a struct that derives [`FromArgs`] must implement
/// this trait. Argp implements it for:
/// * all built-in number types
/// * [`bool`]
/// * [`char`]
/// * [`String`]
/// * [`std::ffi::OsString`]
/// * [`std::path::PathBuf`]
/// * [`std::net::IpAddr`] and its variants
/// * [`std::net::SocketAddr`] and its variants
///
/// Custom types should implement this trait directly.
pub trait FromArgValue: Sized {
    /// Construct the type from a command-line value, returning an error string
    /// on failure.
    fn from_arg_value(value: &OsStr) -> Result<Self, String>;
}

impl FromArgValue for OsString {
    fn from_arg_value(value: &OsStr) -> Result<Self, String> {
        Ok(value.to_os_string())
    }
}

impl FromArgValue for PathBuf {
    fn from_arg_value(value: &OsStr) -> Result<Self, String> {
        Ok(PathBuf::from(value))
    }
}

// XXX: This is a workaround needed until [RFC 1210](https://rust-lang.github.io/rfcs/1210-impl-specialization.html)
// is stabilized.
macro_rules! impl_from_arg_value_from_str {
    ($($ty:ty,)*) => {
        $(
            impl FromArgValue for $ty {
                fn from_arg_value(value: &OsStr) -> Result<Self, String> {
                    use std::str::FromStr;
                    value
                        .to_str()
                        .ok_or("not a valid UTF-8 string".to_owned())
                        .and_then(|s| <$ty>::from_str(s).map_err(|e| e.to_string()))
                }
            }
        )*
    }
}
impl_from_arg_value_from_str![
    bool,
    char,
    String,
    f32,
    f64,
    i128,
    i16,
    i32,
    i64,
    i8,
    isize,
    u128,
    u16,
    u32,
    u64,
    u8,
    usize,
    std::net::IpAddr,
    std::net::Ipv4Addr,
    std::net::Ipv6Addr,
    std::net::SocketAddr,
    std::net::SocketAddrV4,
    std::net::SocketAddrV6,
];

/// Information to display to the user about why a [`FromArgs`] construction
/// exited early.
///
/// This can occur due to either failed parsing or a flag like `--help`.
#[derive(Debug, PartialEq)]
pub enum EarlyExit {
    /// Early exit and display the error message.
    Err(Error),

    /// Early exit and display the help message.
    Help(Help),
}

impl fmt::Display for EarlyExit {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            EarlyExit::Err(err) => err.fmt(f),
            EarlyExit::Help(help) => help.fmt(f),
        }
    }
}

impl From<Error> for EarlyExit {
    fn from(value: Error) -> Self {
        Self::Err(value)
    }
}

/// Create a [`FromArgs`] type from the current process's [`env::args_os()`]
/// with the given [`HelpStyle`]. For the default help style `argp::DEFAULT` can
/// be used.
///
/// This function will exit early from the current process if argument parsing
/// was unsuccessful or if information like `--help` was requested. Error
/// messages will be printed to stderr, and `--help` output to stdout.
pub fn parse_args_or_exit<T: TopLevelCommand>(help_style: &HelpStyle) -> T {
    let args: Vec<_> = env::args_os().collect();
    if args.is_empty() {
        eprintln!("No program name, argv is empty");
        exit(1)
    }
    let cmd = basename(&args[0]);

    T::from_args(&[&cmd], &args[1..]).unwrap_or_else(|early_exit| {
        exit(match early_exit {
            EarlyExit::Help(help) => {
                println!("{}", help.generate(help_style));
                0
            }
            EarlyExit::Err(err) => {
                eprintln!("{}\nRun {} --help for more information.", err, cmd);
                1
            }
        })
    })
}

/// Deprecated alias for [`parse_args_or_exit`].
#[deprecated]
pub fn from_env<T: TopLevelCommand>() -> T {
    parse_args_or_exit(DEFAULT)
}

/// Create a [`FromArgs`] type from the current process's [`env::args_os()`].
///
/// This special cases usages where argp is being used in an environment where
/// cargo is driving the build. We skip the second env variable.
///
/// This function will exit early from the current process if argument parsing
/// was unsuccessful or if information like `--help` was requested. Error
/// messages will be printed to stderr, and `--help` output to stdout.
pub fn cargo_parse_args_or_exit<T: TopLevelCommand>() -> T {
    let args: Vec<_> = env::args_os().collect();
    let cmd = basename(&args[1]);

    T::from_args(&[&cmd], &args[2..]).unwrap_or_else(|early_exit| {
        exit(match early_exit {
            EarlyExit::Help(help) => {
                println!("{}", help.generate_default());
                0
            }
            EarlyExit::Err(err) => {
                eprintln!("{}\nRun --help for more information.", err);
                1
            }
        })
    })
}

/// Extracts the base command from a path.
fn basename(path: &OsStr) -> Cow<'_, str> {
    Path::new(path)
        .file_name()
        .and_then(|s| s.to_str())
        .map(Cow::from)
        .unwrap_or_else(|| path.to_string_lossy())
}

#[cfg(test)]
mod test {
    use super::*;
    use std::ffi::OsString;

    #[test]
    fn test_basename() {
        let expected = "test_cmd";
        let path = OsString::from(format!("/tmp/{}", expected));
        let cmd = basename(&path);
        assert_eq!(expected, cmd);
    }
}