Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
840 lines (830 sloc) 29 KB
// Copyright 2018 Guillaume Pinot (@TeXitoi) <texitoi@texitoi.eu>
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![deny(missing_docs)]
//! This crate defines the `StructOpt` trait and its custom derive.
//!
//! ## Features
//!
//! If you want to disable all the `clap` features (colors,
//! suggestions, ..) add `default-features = false` to the `structopt`
//! dependency:
//!
//! ```toml
//! [dependencies]
//! structopt = { version = "0.3", default-features = false }
//! ```
//!
//! Support for [`paw`](https://github.com/rust-cli/paw) (the
//! `Command line argument paw-rser abstraction for main`) is disabled
//! by default, but can be enabled in the `structopt` dependency
//! with the feature `paw`:
//!
//! ```toml
//! [dependencies]
//! structopt = { version = "0.3", features = [ "paw" ] }
//! paw = "1.0"
//! ```
//!
//! # Table of Contents
//!
//! - [How to `derive(StructOpt)`](#how-to-derivestructopt)
//! - [Attributes](#attributes)
//! - [Raw methods](#raw-methods)
//! - [Magical methods](#magical-methods)
//! - Arguments
//! - [Type magic](#type-magic)
//! - [Specifying argument types](#specifying-argument-types)
//! - [Help messages](#help-messages)
//! - [Environment variable fallback](#environment-variable-fallback)
//! - [Skipping fields](#skipping-fields)
//! - [Subcommands](#subcommands)
//! - [Optional subcommands](#optional-subcommands)
//! - [Flattening](#flattening)
//! - [Custom string parsers](#custom-string-parsers)
//!
//!
//!
//! ## How to `derive(StructOpt)`
//!
//! First, let's look at the example:
//!
//! ```should_panic
//! use std::path::PathBuf;
//! use structopt::StructOpt;
//!
//! #[derive(Debug, StructOpt)]
//! #[structopt(name = "example", about = "An example of StructOpt usage.")]
//! struct Opt {
//! /// Activate debug mode
//! // short and long flags (-d, --debug) will be deduced from the field's name
//! #[structopt(short, long)]
//! debug: bool,
//!
//! /// Set speed
//! // we don't want to name it "speed", need to look smart
//! #[structopt(short = "v", long = "velocity", default_value = "42")]
//! speed: f64,
//!
//! /// Input file
//! #[structopt(parse(from_os_str))]
//! input: PathBuf,
//!
//! /// Output file, stdout if not present
//! #[structopt(parse(from_os_str))]
//! output: Option<PathBuf>,
//!
//! /// Where to write the output: to `stdout` or `file`
//! #[structopt(short)]
//! out_type: String,
//!
//! /// File name: only required when `out` is set to `file`
//! #[structopt(name = "FILE", required_if("out_type", "file"))]
//! file_name: String,
//! }
//!
//! fn main() {
//! let opt = Opt::from_args();
//! println!("{:?}", opt);
//! }
//! ```
//!
//! So `derive(StructOpt)` tells Rust to generate a command line parser,
//! and the various `structopt` attributes are simply
//! used for additional parameters.
//!
//! First, define a struct, whatever its name. This structure
//! corresponds to a `clap::App`, its fields correspond to `clap::Arg`
//! (unless they're [subcommands](#subcommands)),
//! and you can adjust these apps and args by `#[structopt(...)]` [attributes](#attributes).
//!
//! **Note:**
//! _________________
//! Keep in mind that `StructOpt` trait is more than just `from_args` method.
//! It has a number of additional features, including access to underlying
//! `clap::App` via `StructOpt::clap()`. See the
//! [trait's reference documentation](trait.StructOpt.html).
//! _________________
//!
//! ## Attributes
//!
//! `#[structopt(...)]` attributes fall into two categories:
//! - `structopt`'s own [magical methods](#magical-methods).
//!
//! They are used by `structopt` itself. They come mostly in
//! `attr = ["whatever"]` form, but some `attr(args...)` also exist.
//!
//! - [`raw` attributes](#raw-methods).
//!
//! They represent explicit `clap::Arg/App` method calls.
//! They are what used to be explicit `#[structopt(raw(...))]` attrs in pre-0.3 `structopt`
//!
//! Every `structopt attribute` looks like comma-separated sequence of methods:
//! ```rust,ignore
//! #[structopt(
//! short, // method with no arguments - always magical
//! long = "--long-option", // method with one argument
//! required_if("out", "file"), // method with one and more args
//! parse(from_os_str = path::to::parser) // some magical methods have their own syntax
//! )]
//! ```
//!
//! `#[structopt(...)]` attributes can be placed on top of `struct`, `enum`,
//! `struct` field or `enum` variant. Attributes on top of `struct` or `enum`
//! represent `clap::App` method calls, field or variant attributes correspond
//! to `clap::Arg` method calls.
//!
//! In other words, the `Opt` struct from the example above
//! will be turned into this (*details omitted*):
//!
//! ```
//! # use structopt::clap::{Arg, App};
//! App::new("example")
//! .version("0.2.0")
//! .about("An example of StructOpt usage.")
//! .arg(Arg::with_name("debug")
//! .help("Activate debug mode")
//! .short("debug")
//! .long("debug"))
//! .arg(Arg::with_name("speed")
//! .help("Set speed")
//! .short("v")
//! .long("velocity")
//! .default_value("42"))
//! // and so on
//! # ;
//! ```
//!
//! ## Raw methods
//!
//! They are the reason why `structopt` is so flexible.
//!
//! Each and every method from `clap::App` and `clap::Arg` can be used directly -
//! just `#[structopt(method_name = single_arg)]` or `#[structopt(method_name(arg1, arg2))]`
//! and it just works. As long as `method_name` is not one of the magical methods -
//! it's just a method call.
//!
//! **Note:**
//! _________________
//!
//! "Raw methods" are direct replacement for pre-0.3 structopt's
//! `#[structopt(raw(...))]` attributes, any time you would have used a `raw()` attribute
//! in 0.2 you should use raw method in 0.3.
//!
//! Unfortunately, old raw attributes collide with `clap::Arg::raw` method. To explicitly
//! warn users of this change we allow `#[structopt(raw())]` only with `true` or `false`
//! literals (this method is supposed to be called only with `true` anyway).
//! __________________
//!
//! ## Magical methods
//!
//! They are the reason why `structopt` is so easy to use and convenient in most cases.
//! Many of them have defaults, some of them get used even if not mentioned.
//!
//! Methods may be used on "top level" (on top of a `struct`, `enum` or `enum` variant)
//! and/or on "field-level" (on top of a `struct` field or *inside* of an enum variant).
//! Top level (non-magical) methods correspond to `App::method` calls, field-level methods
//! are `Arg::method` calls.
//!
//! ```ignore
//! #[structopt(top_level)]
//! struct Foo {
//! #[structopt(field_level)]
//! field: u32
//! }
//!
//! #[structopt(top_level)]
//! enum Bar {
//! #[structopt(top_level)]
//! Pineapple {
//! #[structopt(field_level)]
//! chocolate: String
//! },
//!
//! #[structopt(top_level)]
//! Orange,
//! }
//! ```
//!
//! - `name`: `[name = "name"]`
//! - On top level: `App::new("name")`.
//!
//! The binary name displayed in help messages. Defaults to the crate name given by Cargo.
//!
//! - On field-level: `Arg::with_name("name")`.
//!
//! The name for the argument the field stands for, this name appears in help messages.
//! Defaults to a name, deduced from a field, see also
//! [`rename_all`](#specifying-argument-types).
//!
//! - `version`: `[version = "version"]`
//!
//! Usable only on top level: `App::version("version" or env!(CARGO_PKG_VERSION))`.
//!
//! The version displayed in help messages.
//! Defaults to the crate version given by Cargo. If `CARGO_PKG_VERSION` is not
//! set no `.version()` calls will be generated unless requested.
//!
//! - `no_version`: `no_version`
//!
//! Usable only on top level. Prevents default `App::version` call, i.e
//! when no `version = "version"` mentioned.
//!
//! - `author`: `author [= "author"]`
//!
//! Usable only on top level: `App::author("author" or env!(CARGO_PKG_AUTHOR))`.
//!
//! Author/maintainer of the binary, this name appears in help messages.
//! Defaults to the crate author given by cargo, but only when `author` explicitly mentioned.
//!
//! - `about`: `about [= "about"]`
//!
//! Usable only on top level: `App::about("about" or env!(CARGO_PKG_DESCRIPTION))`.
//!
//! Short description of the binary, appears in help messages.
//! Defaults to the crate description given by cargo,
//! but only when `about` explicitly mentioned.
//!
//! - [`short`](#specifying-argument-types): `short [= "short-opt-name"]`
//!
//! Usable only on field-level.
//!
//! - [`long`](#specifying-argument-types): `long [= "long-opt-name"]`
//!
//! Usable only on field-level.
//!
//! - [`rename_all`](#specifying-argument-types): [`rename_all = "kebab"/"snake"/"screaming-snake"/"camel"/"pascal"/"verbatim"]`
//!
//! Usable only on top level
//!
//! - [`parse`](#custom-string-parsers): `parse(type [= path::to::parser::fn])`
//!
//! Usable only on field-level.
//!
//! - [`skip`](#skipping-fields): `skip = [expr]`
//!
//! Usable only on field-level.
//!
//! - [`flatten`](#flattening): `flatten`
//!
//! Usable only on field-level.
//!
//! - [`subcommand`](#subcommands): `subcommand`
//!
//! Usable only on field-level.
//!
//! ## Type magic
//!
//! One of major things that makes `structopt` so awesome is it's type magic.
//! Do you want optional positional argument? Use `Option<T>`! Or perhaps optional argument
//! that optionally takes value (`[--opt=[val]]`)? Use `Option<Option<T>>`!
//!
//! Here is the table of types and `clap` methods they correspond to:
//!
//! Type | Effect | Added method call to `clap::Arg`
//! -----------------------------|---------------------------------------------------|--------------------------------------
//! `bool` | `true` if the flag is present | `.takes_value(false).multiple(false)`
//! `Option<T: FromStr>` | optional positional argument or option | `.takes_value(true).multiple(false)`
//! `Option<Option<T: FromStr>>` | optional option with optional value | `.takes_value(true).multiple(false).min_values(0).max_values(1)`
//! `Vec<T: FromStr>` | list of options or the other positional arguments | `.takes_value(true).multiple(true)`
//! `Option<Vec<T: FromStr>` | optional list of options | `.takes_values(true).multiple(true).min_values(0)`
//! `T: FromStr` | required option or positional argument | `.takes_value(true).multiple(false).required(!has_default)`
//!
//! The `FromStr` trait is used to convert the argument to the given
//! type, and the `Arg::validator` method is set to a method using
//! `to_string()` (`FromStr::Err` must implement `std::fmt::Display`).
//! If you would like to use a custom string parser other than `FromStr`, see
//! the [same titled section](#custom-string-parsers) below.
//!
//! **Note:**
//! _________________
//! Pay attention that *only literal occurrence* of this types is special, for example
//! `Option<T>` is special while `::std::option::Option<T>` is not.
//!
//! If you need to avoid special casing you can make a `type` alias and
//! use it in place of the said type.
//! _________________
//!
//! **Note:**
//! _________________
//! `bool` cannot be used as positional argument unless you provide an explicit parser.
//! If you need a positional bool, for example to parse `true` or `false`, you must
//! annotate the field with explicit [`#[structopt(parse(...))]`](#custom-string-parsers).
//! _________________
//!
//! Thus, the `speed` argument is generated as:
//!
//! ```
//! # extern crate clap;
//! # fn parse_validator<T>(_: String) -> Result<(), String> { unimplemented!() }
//! # fn main() {
//! clap::Arg::with_name("speed")
//! .takes_value(true)
//! .multiple(false)
//! .required(false)
//! .validator(parse_validator::<f64>)
//! .short("v")
//! .long("velocity")
//! .help("Set speed")
//! .default_value("42");
//! # }
//! ```
//!
//! ## Specifying argument types
//!
//! There are three types of arguments that can be supplied to each
//! (sub-)command:
//!
//! - short (e.g. `-h`),
//! - long (e.g. `--help`)
//! - and positional.
//!
//! Like clap, structopt defaults to creating positional arguments.
//!
//! If you want to generate a long argument you can specify either
//! `long = $NAME`, or just `long` to get a long flag generated using
//! the field name. The generated casing style can be modified using
//! the `rename_all` attribute. See the `rename_all` example for more.
//!
//! For short arguments, `short` will use the first letter of the
//! field name by default, but just like the long option it's also
//! possible to use a custom letter through `short = $LETTER`.
//!
//! If an argument is renamed using `name = $NAME` any following call to
//! `short` or `long` will use the new name.
//!
//! **Attention**: If these arguments are used without an explicit name
//! the resulting flag is going to be renamed using `kebab-case` if the
//! `rename_all` attribute was not specified previously. The same is true
//! for subcommands with implicit naming through the related data structure.
//!
//! ```
//! use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! #[structopt(rename_all = "kebab-case")]
//! struct Opt {
//! /// This option can be specified with something like `--foo-option
//! /// value` or `--foo-option=value`
//! #[structopt(long)]
//! foo_option: String,
//!
//! /// This option can be specified with something like `-b value` (but
//! /// not `--bar-option value`).
//! #[structopt(short)]
//! bar_option: String,
//!
//! /// This option can be specified either `--baz value` or `-z value`.
//! #[structopt(short = "z", long = "baz")]
//! baz_option: String,
//!
//! /// This option can be specified either by `--custom value` or
//! /// `-c value`.
//! #[structopt(name = "custom", long, short)]
//! custom_option: String,
//!
//! /// This option is positional, meaning it is the first unadorned string
//! /// you provide (multiple others could follow).
//! my_positional: String,
//!
//! /// This option is skipped and will be filled with the default value
//! /// for its type (in this case 0).
//! #[structopt(skip)]
//! skipped: u32,
//!
//! }
//!
//! # fn main() {
//! # Opt::from_clap(&Opt::clap().get_matches_from(
//! # &["test", "--foo-option", "", "-b", "", "--baz", "", "--custom", "", "positional"]));
//! # }
//! ```
//!
//! ## Help messages
//!
//! Help messages for the whole binary or individual arguments can be
//! specified using the `about` attribute on the struct and the `help`
//! attribute on the field, as we've already seen. For convenience,
//! they can also be specified using doc comments. For example:
//!
//! ```
//! # use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! /// The help message that will be displayed when passing `--help`.
//! struct Foo {
//! #[structopt(short)]
//! /// The description for the arg that will be displayed when passing `--help`.
//! bar: String
//! }
//! # fn main() {}
//! ```
//!
//! If it is necessary or wanted to provide a more complex help message then the
//! previous used ones, it could still be a good idea to distinguish between the
//! actual help message a short summary. In this case `about` and `help` should
//! only contain the short and concise form while the two additional arguments
//! `long_about` and `long_help` can be used to store a descriptive and more in
//! depth message.
//!
//! If both - the short and the long version of the argument - are present,
//! the user can later chose between the short summary (`-h`) and the long
//! descriptive version (`--help`) of the help message. Also in case
//! of subcommands the short help message will automatically be used for the
//! command description inside the parents help message and the long version
//! as command description if help is requested on the actual subcommand.
//!
//! This feature can also be used with doc comments instead of arguments through
//! proper comment formatting. To be activated it requires, that the first line
//! of the comment is separated from the rest of the comment through an empty line.
//! In this case the first line is used as summary and the whole comment represents
//! the long descriptive message.
//!
//! ```
//! # use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! /// The help message that will be displayed when passing `--help`.
//! struct Foo {
//! #[structopt(short)]
//! /// Only this summary is visible when passing `-h`.
//! ///
//! /// But the whole comment will be displayed when passing `--help`.
//! /// This could be quite useful to provide further hints are usage
//! /// examples.
//! bar: String
//! }
//! # fn main() {}
//! ```
//!
//! ## Environment variable fallback
//!
//! It is possible to specify an environment variable fallback option for an arguments
//! so that its value is taken from the specified environment variable if not
//! given through the command-line:
//!
//! ```
//! # use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! struct Foo {
//! #[structopt(short, long, env = "PARAMETER_VALUE")]
//! parameter_value: String
//! }
//! # fn main() {}
//! ```
//!
//! By default, values from the environment are shown in the help output (i.e. when invoking
//! `--help`):
//!
//! ```shell
//! $ cargo run -- --help
//! ...
//! OPTIONS:
//! -p, --parameter-value <parameter-value> [env: PARAMETER_VALUE=env_value]
//! ```
//!
//! In some cases this may be undesirable, for example when being used for passing
//! credentials or secret tokens. In those cases you can use `hide_env_values` to avoid
//! having strucopt emit the actual secret values:
//! ```
//! # use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! struct Foo {
//! #[structopt(long = "secret", env = "SECRET_VALUE", hide_env_values = true)]
//! secret_value: String
//! }
//! ```
//!
//! ### Auto-deriving environment variables
//!
//! Environment variables tend to be called after the corresponding `struct`'s field,
//! as in example above. The field is `secret_value` and the env var is "SECRET_VALUE";
//! the name is the same, except casing is different.
//!
//! It's pretty tedious and error-prone to type the same name twice,
//! so you can ask `structopt` to do that for you.
//!
//! ```
//! # use structopt::StructOpt;
//!
//! #[derive(StructOpt)]
//! struct Foo {
//! #[structopt(long = "secret", env)]
//! secret_value: String
//! }
//! ```
//!
//! It works just like `#[structopt(short/long)]`: if `env` is not set to some concrete
//! value the value will be derived from the field's name. This is controlled by
//! `#[structopt(rename_all_env)]`.
//!
//! `rename_all_env` works exactly as `rename_all` (including overriding)
//! except default casing is `SCREAMING_SNAKE_CASE` instead of `kebab-case`.
//!
//! ## Skipping fields
//!
//! Sometimes you may want to add a field to your `Opt` struct that is not
//! a command line option and `clap` should know nothing about it. You can ask
//! `structopt` to skip the field entirely via `#[structopt(skip = value)]`
//! (`value` must implement `Into<FieldType>`)
//! or `#[structopt(skip)]` if you want assign the field with `Default::default()`
//! (obviously, the field's type must implement `Default`).
//!
//! ```
//! # use structopt::StructOpt;
//! #[derive(StructOpt)]
//! pub struct Opt {
//! #[structopt(long, short)]
//! number: u32,
//!
//! // these fields are to be assigned with Default::default()
//!
//! #[structopt(skip)]
//! k: String,
//! #[structopt(skip)]
//! v: Vec<u32>,
//!
//! // these fields get set explicitly
//!
//! #[structopt(skip = vec![1, 2, 3])]
//! k2: Vec<u32>,
//! #[structopt(skip = "cake")] // &str implements Into<String>
//! v2: String,
//! }
//! ```
//!
//! ## Subcommands
//!
//! Some applications, especially large ones, split their functionality
//! through the use of "subcommands". Each of these act somewhat like a separate
//! command, but is part of the larger group.
//! One example is `git`, which has subcommands such as `add`, `commit`,
//! and `clone`, to mention just a few.
//!
//! `clap` has this functionality, and `structopt` supports it through enums:
//!
//! ```
//! # use structopt::StructOpt;
//!
//! # use std::path::PathBuf;
//! #[derive(StructOpt)]
//! #[structopt(about = "the stupid content tracker")]
//! enum Git {
//! Add {
//! #[structopt(short)]
//! interactive: bool,
//! #[structopt(short)]
//! patch: bool,
//! #[structopt(parse(from_os_str))]
//! files: Vec<PathBuf>
//! },
//! Fetch {
//! #[structopt(long)]
//! dry_run: bool,
//! #[structopt(long)]
//! all: bool,
//! repository: Option<String>
//! },
//! Commit {
//! #[structopt(short)]
//! message: Option<String>,
//! #[structopt(short)]
//! all: bool
//! }
//! }
//! # fn main() {}
//! ```
//!
//! Using `derive(StructOpt)` on an enum instead of a struct will produce
//! a `clap::App` that only takes subcommands. So `git add`, `git fetch`,
//! and `git commit` would be commands allowed for the above example.
//!
//! `structopt` also provides support for applications where certain flags
//! need to apply to all subcommands, as well as nested subcommands:
//!
//! ```
//! # use structopt::StructOpt;
//! # fn main() {}
//! #[derive(StructOpt)]
//! struct MakeCookie {
//! #[structopt(name = "supervisor", default_value = "Puck", long = "supervisor")]
//! supervising_faerie: String,
//! /// The faerie tree this cookie is being made in.
//! tree: Option<String>,
//! #[structopt(subcommand)] // Note that we mark a field as a subcommand
//! cmd: Command
//! }
//!
//! #[derive(StructOpt)]
//! enum Command {
//! /// Pound acorns into flour for cookie dough.
//! Pound {
//! acorns: u32
//! },
//! /// Add magical sparkles -- the secret ingredient!
//! Sparkle {
//! #[structopt(short, parse(from_occurrences))]
//! magicality: u64,
//! #[structopt(short)]
//! color: String
//! },
//! Finish(Finish),
//! }
//!
//! // Subcommand can also be externalized by using a 1-uple enum variant
//! #[derive(StructOpt)]
//! struct Finish {
//! #[structopt(short)]
//! time: u32,
//! #[structopt(subcommand)] // Note that we mark a field as a subcommand
//! finish_type: FinishType
//! }
//!
//! // subsubcommand!
//! #[derive(StructOpt)]
//! enum FinishType {
//! Glaze {
//! applications: u32
//! },
//! Powder {
//! flavor: String,
//! dips: u32
//! }
//! }
//! ```
//!
//! Marking a field with `structopt(subcommand)` will add the subcommands of the
//! designated enum to the current `clap::App`. The designated enum *must* also
//! be derived `StructOpt`. So the above example would take the following
//! commands:
//!
//! + `make-cookie pound 50`
//! + `make-cookie sparkle -mmm --color "green"`
//! + `make-cookie finish 130 glaze 3`
//!
//! ### Optional subcommands
//!
//! Subcommands may be optional:
//!
//! ```
//! # use structopt::StructOpt;
//! # fn main() {}
//! #[derive(StructOpt)]
//! struct Foo {
//! file: String,
//! #[structopt(subcommand)]
//! cmd: Option<Command>
//! }
//!
//! #[derive(StructOpt)]
//! enum Command {
//! Bar,
//! Baz,
//! Quux
//! }
//! ```
//!
//! ## Flattening
//!
//! It can sometimes be useful to group related arguments in a substruct,
//! while keeping the command-line interface flat. In these cases you can mark
//! a field as `flatten` and give it another type that derives `StructOpt`:
//!
//! ```
//! # use structopt::StructOpt;
//! # fn main() {}
//! #[derive(StructOpt)]
//! struct Cmdline {
//! /// switch on verbosity
//! #[structopt(short)]
//! verbose: bool,
//! #[structopt(flatten)]
//! daemon_opts: DaemonOpts,
//! }
//!
//! #[derive(StructOpt)]
//! struct DaemonOpts {
//! /// daemon user
//! #[structopt(short)]
//! user: String,
//! /// daemon group
//! #[structopt(short)]
//! group: String,
//! }
//! ```
//!
//! In this example, the derived `Cmdline` parser will support the options `-v`,
//! `-u` and `-g`.
//!
//! This feature also makes it possible to define a `StructOpt` struct in a
//! library, parse the corresponding arguments in the main argument parser, and
//! pass off this struct to a handler provided by that library.
//!
//! ## Custom string parsers
//!
//! If the field type does not have a `FromStr` implementation, or you would
//! like to provide a custom parsing scheme other than `FromStr`, you may
//! provide a custom string parser using `parse(...)` like this:
//!
//! ```
//! # use structopt::StructOpt;
//! # fn main() {}
//! use std::num::ParseIntError;
//! use std::path::PathBuf;
//!
//! fn parse_hex(src: &str) -> Result<u32, ParseIntError> {
//! u32::from_str_radix(src, 16)
//! }
//!
//! #[derive(StructOpt)]
//! struct HexReader {
//! #[structopt(short, parse(try_from_str = parse_hex))]
//! number: u32,
//! #[structopt(short, parse(from_os_str))]
//! output: PathBuf,
//! }
//! ```
//!
//! There are five kinds of custom parsers:
//!
//! | Kind | Signature | Default |
//! |-------------------|---------------------------------------|---------------------------------|
//! | `from_str` | `fn(&str) -> T` | `::std::convert::From::from` |
//! | `try_from_str` | `fn(&str) -> Result<T, E>` | `::std::str::FromStr::from_str` |
//! | `from_os_str` | `fn(&OsStr) -> T` | `::std::convert::From::from` |
//! | `try_from_os_str` | `fn(&OsStr) -> Result<T, OsString>` | (no default function) |
//! | `from_occurrences`| `fn(u64) -> T` | `value as T` |
//! | `from_flag` | `fn(bool) -> T` | `::std::convert::From::from` |
//!
//! The `from_occurrences` parser is special. Using `parse(from_occurrences)`
//! results in the _number of flags occurrences_ being stored in the relevant
//! field or being passed to the supplied function. In other words, it converts
//! something like `-vvv` to `3`. This is equivalent to
//! `.takes_value(false).multiple(true)`. Note that the default parser can only
//! be used with fields of integer types (`u8`, `usize`, `i64`, etc.).
//!
//! The `from_flag` parser is also special. Using `parse(from_flag)` or
//! `parse(from_flag = some_func)` will result in the field being treated as a
//! flag even if it does not have type `bool`.
//!
//! When supplying a custom string parser, `bool` will not be treated specially:
//!
//! Type | Effect | Added method call to `clap::Arg`
//! ------------|-------------------|--------------------------------------
//! `Option<T>` | optional argument | `.takes_value(true).multiple(false)`
//! `Vec<T>` | list of arguments | `.takes_value(true).multiple(true)`
//! `T` | required argument | `.takes_value(true).multiple(false).required(!has_default)`
//!
//! In the `try_from_*` variants, the function will run twice on valid input:
//! once to validate, and once to parse. Hence, make sure the function is
//! side-effect-free.
#[doc(hidden)]
pub use structopt_derive::*;
use std::ffi::OsString;
/// Re-export of clap
pub use clap;
/// A struct that is converted from command line arguments.
pub trait StructOpt {
/// Returns the corresponding `clap::App`.
fn clap<'a, 'b>() -> clap::App<'a, 'b>;
/// Creates the struct from `clap::ArgMatches`. It cannot fail
/// with a parameter generated by `clap` by construction.
fn from_clap(matches: &clap::ArgMatches<'_>) -> Self;
/// Gets the struct from the command line arguments. Print the
/// error message and quit the program in case of failure.
fn from_args() -> Self
where
Self: Sized,
{
Self::from_clap(&Self::clap().get_matches())
}
/// Gets the struct from any iterator such as a `Vec` of your making.
/// Print the error message and quit the program in case of failure.
fn from_iter<I>(iter: I) -> Self
where
Self: Sized,
I: IntoIterator,
I::Item: Into<OsString> + Clone,
{
Self::from_clap(&Self::clap().get_matches_from(iter))
}
/// Gets the struct from any iterator such as a `Vec` of your making.
///
/// Returns a `clap::Error` in case of failure. This does *not* exit in the
/// case of `--help` or `--version`, to achieve the same behavior as
/// `from_iter()` you must call `.exit()` on the error value.
fn from_iter_safe<I>(iter: I) -> Result<Self, clap::Error>
where
Self: Sized,
I: IntoIterator,
I::Item: Into<OsString> + Clone,
{
Ok(Self::from_clap(&Self::clap().get_matches_from_safe(iter)?))
}
}
You can’t perform that action at this time.