Docopt for Rust with automatic type based decoding (i.e., data validation). This implementation conforms to the official description of Docopt and passes its test suite.
Licensed under the UNLICENSE.
Current status
Fully functional but the design of the API is up for debate. I am seeking feedback.
Documentation
http://burntsushi.net/rustdoc/docopt
Installation
This crate is fully compatible with Cargo. Just add it to your Cargo.toml
:
[dependencies.docopt_macros]
git = "git://github.com/docopt/docopt.rs"
If you don't want to use the macro, then you can change your entry to
dependencies.docopt
.
Quick example
Here is a full working example:
extern crate serialize;
extern crate docopt;
use docopt::Docopt;
// Write the Docopt usage string.
static USAGE: &'static str = "
Usage: cp [-a] <source> <dest>
cp [-a] <source>... <dir>
Options:
-a, --archive Copy everything.
";
#[deriving(Decodable, Show)]
struct Args {
arg_source: Vec<String>,
arg_dest: String,
arg_dir: String,
flag_archive: bool,
}
fn main() {
let args: Args = Docopt::new(USAGE)
.and_then(|d| d.decode())
.unwrap_or_else(|e| e.exit());
println!("{}", args);
}
Here is the same example, but with the use of the docopt!
macro, which will
generate a struct for you:
#![feature(phase)]
extern crate serialize;
extern crate docopt;
#[phase(plugin)] extern crate docopt_macros;
docopt!(Args deriving Show, "
Usage: cp [options] <src> <dst>
cp [options] <src>... <dir>
cp --help
Options:
-h, --help Show this message.
-a, --archive Copy everything.
")
fn main() {
let args: Args = Args::docopt().decode().unwrap_or_else(|e| e.exit());
println!("{}", args);
}
The field names of the struct map like this:
-g => flag_g
--group => flag_group
FILE => arg_FILE
<file> => arg_file
build => cmd_build
The Args
struct has one static method defined for it: docopt
. The method
returns a normal Docopt
value, which can be used to set configuration
options, argv
and parse or decode command line arguments.
Data validation example
Here's another example that shows how to specify the types of your arguments:
#![feature(phase)]
extern crate serialize;
extern crate docopt;
#[phase(plugin)] extern crate docopt_macros;
docopt!(Args, "Usage: add <x> <y>", arg_x: int, arg_y: int)
fn main() {
let args: Args = Args::docopt().decode().unwrap_or_else(|e| e.exit());
println!("x: {:d}, y: {:d}", args.arg_x, args.arg_y);
}
In this example, specific type annotations were added. They will be
automatically inserted into the generated struct. You can override as many (or
as few) fields as you want. If you don't specify a type, then one of bool
,
uint
, String
or Vec<String>
will be chosen depending on the type of
argument. In this case, both arg_x
and arg_y
would have been String
.
If any value cannot be decoded into a value with the right type, then an error will be shown to the user.
And of course, you don't need the macro to do this. You can do the same thing with a manually written struct too.
rustc
Modeling Here's a selected subset for some of rustc
's options. This also shows how to
restrict values to a list of choices via an enum
type and demonstrates more
Docopt features.
#![feature(phase)]
extern crate serialize;
extern crate docopt;
#[phase(plugin)] extern crate docopt_macros;
docopt!(Args deriving Show, "
Usage: rustc [options] [--cfg SPEC... -L PATH...] INPUT
rustc (--help | --version)
Options:
-h, --help Show this message.
--version Show the version of rustc.
--cfg SPEC Configure the compilation environment.
-L PATH Add a directory to the library search path.
--emit TYPE Configure the output that rustc will produce.
Valid values: asm, ir, bc, obj, link.
--opt-level LEVEL Optimize with possible levels 0-3.
", flag_opt_level: Option<OptLevel>, flag_emit: Option<Emit>)
#[deriving(Decodable, Show)]
enum Emit { Asm, Ir, Bc, Obj, Link }
#[deriving(Show)]
enum OptLevel { Zero, One, Two, Three }
impl<E, D: serialize::Decoder<E>> serialize::Decodable<D, E> for OptLevel {
fn decode(d: &mut D) -> Result<OptLevel, E> {
Ok(match try!(d.read_uint()) {
0 => Zero, 1 => One, 2 => Two, 3 => Three,
n => {
let err = format!("Could not decode '{}' as opt-level.", n);
return Err(d.error(err.as_slice()));
}
})
}
}
fn main() {
let args: Args = Args::docopt().decode().unwrap_or_else(|e| e.exit());
println!("{}", args);
}
Viewing the generated struct
Generating a struct is pretty magical, but if you want, you can look at it by
expanding all macros. Say you wrote the above example for Usage: add <x> <y>
into a file called add.rs
. Then running:
rustc -L path/containing/docopt/lib --pretty expanded add.rs
Will show all macros expanded. In the generated code, you should be able to find the generated struct:
struct Args {
pub arg_x: int,
pub arg_y: int,
}
Traditional Docopt API
The reference implementation of Docopt returns a Python dictionary with names
like <arg>
or --flag
. If you prefer this access pattern, then you can use
docopt::ArgvMap
. The disadvantage is that you have to do all of your type
conversion manually. Here's the canonical Docopt example with a hash table:
extern crate docopt;
use docopt::Docopt;
static USAGE: &'static str = "
Naval Fate.
Usage:
naval_fate.py ship new <name>...
naval_fate.py ship <name> move <x> <y> [--speed=<kn>]
naval_fate.py ship shoot <x> <y>
naval_fate.py mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate.py (-h | --help)
naval_fate.py --version
Options:
-h --help Show this screen.
--version Show version.
--speed=<kn> Speed in knots [default: 10].
--moored Moored (anchored) mine.
--drifting Drifting mine.
";
fn main() {
let args = Docopt::new(USAGE)
.and_then(|dopt| dopt.parse())
.unwrap_or_else(|e| e.exit());
println!("{}", args);
// You can conveniently access values with `get_{bool,count,str,vec}`
// functions. If the key doesn't exist (or if, e.g., you use `get_str` on
// a switch), then a sensible default value is returned.
println!("\nSome values:");
println!(" Speed: {}", args.get_str("--speed"));
println!(" Drifting? {}", args.get_bool("--drifting"));
println!(" Names: {}", args.get_vec("<name>"));
}
Tab completion support
This particular implementation bundles a command called docopt-wordlist
that
can be used to automate tab completion. This repository also collects some
basic completion support for various shells (currently only bash) in the
completions
directory.
You can use them to setup tab completion on your system. It should work with
any program that uses Docopt (or rather, any program that outputs usage
messages that look like Docopt). For example, to get tab completion support for
Cargo, you'll have to install docopt-wordlist
and add some voodoo to your
$HOME/.bash_completion
file (this may vary for other shells).
Here it is step by step:
# Download and build `docopt-wordlist` (as part of the Docopt package)
$ git clone git://github.com/docopt/docopt.rs
$ cd docopt.rs
$ cargo build --release
# Now setup tab completion (for bash)
$ echo "DOCOPT_WORDLIST_BIN=\"$(pwd)/target/release/docopt-wordlist\"" >> $HOME/.bash_completion
$ echo "source \"$(pwd)/completions/docopt-wordlist.bash\"" >> $HOME/.bash_completion
$ echo "complete -F _docopt_wordlist_commands cargo" >> $HOME/.bash_completion
My CSV toolkit is supported too:
# shameless plug...
$ echo "complete -F _docopt_wordlist_commands xsv" >> $HOME/.bash_completion
Note that this is emphatically a first pass. There are several improvements that I'd like to make:
- Take context into account when completing. For example, it should be possible to only show completions that can lead to a valid Docopt match. This may be hard. (i.e., It may require restructuring Docopt's internals.)
- Support more shells. (I'll happily accept pull requests on this one. I doubt I'll venture outside of bash any time soon.)
- Make tab completion support more seamless. The way it works right now is pretty hacky by intermingling file/directory completion.