Struct ParseCon 

pub struct ParseCon<P> {
    pub inner: P,
    pub meta: Meta,
    pub failfast: bool,
}

Create parser from a function, construct! uses it internally

Fields

inner: P

inner parser closure

meta: Meta

metas for inner parsers

failfast: bool

To produce a better error messages while parsing constructed values we want to look at all the items so values that can be consumed are consumed autocomplete relies on the same logic

However when dealing with adjacent restriction detecting the first item relies on failing fast

Implementations

impl<T> ParseCon<T>

pub fn adjacent(self) -> ParseAdjacent<Self>

Automagically restrict the inner parser scope to accept adjacent values only

adjacent can solve surprisingly wide variety of problems: sequential command chaining, multi-value arguments, option-structs to name a few. If you want to run a parser on a sequential subset of arguments - adjacent might be able to help you. Check the examples for better intuition.

Let’s consider two examples with consumed items marked in bold and constructor containing parsers for -c and -d.

• -a -b -c -d
• -a -c -b -d

In the first example -b breaks the adjacency for all the consumed items so parsing will fail, while here in the second one all the consumed items are adjacent to each other so parsing will succeed.

Multi-value arguments

Parsing things like --point X Y Z

Combinatoric example

#[derive(Debug, Clone)]
pub struct Options {
    point: Vec<Point>,
    rotate: bool,
}

#[derive(Debug, Clone)]
struct Point {
    point: (),
    x: usize,
    y: usize,
    z: f64,
}

fn point() -> impl Parser<Point> {
    let point = short('p')
        .long("point")
        .help("Point coordinates")
        .req_flag(());
    let x = positional::<usize>("X").help("X coordinate of a point");
    let y = positional::<usize>("Y").help("Y coordinate of a point");
    let z = positional::<f64>("Z").help("Height of a point above the plane");
    construct!(Point { point, x, y, z }).adjacent()
}

pub fn options() -> OptionParser<Options> {
    let rotate = short('r')
        .long("rotate")
        .help("Face the camera towards the first point")
        .switch();
    let point = point().many();
    construct!(Options { point, rotate }).to_options()
}

fn main() {
    println!("{:?}", options().run())
}

Derive example

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub struct Options {
    #[bpaf(external, many)]
    point: Vec<Point>,
    #[bpaf(short, long)]
    /// Face the camera towards the first point
    rotate: bool,
}

#[derive(Debug, Clone, Bpaf)]
#[bpaf(adjacent)]
struct Point {
    #[bpaf(short, long)]
    /// Point coordinates
    point: (),
    #[bpaf(positional("X"))]
    /// X coordinate of a point
    x: usize,
    #[bpaf(positional("Y"))]
    /// Y coordinate of a point
    y: usize,
    #[bpaf(positional("Z"))]
    /// Height of a point above the plane
    z: f64,
}

fn main() {
    println!("{:?}", options().run())
}

Output

Fields can have different types, including Option or Vec, in this example they are two usize and one f64.

$ app --help

Usage: app [-p X Y Z]... [-r]

Available options:

-p X Y Z

-p, --point

Point coordinates

X

X coordinate of a point

Y

Y coordinate of a point

Z

Height of a point above the plane

-r, --rotate

Face the camera towards the first point

-h, --help

Prints help information

flag --point takes 3 positional arguments: two integers for X and Y coordinates and one floating point for height, order is important, switch --rotate can go on either side of it

$ app --rotate --point 10 20 3.1415
Options { point: [Point { point: (), x: 10, y: 20, z: 3.1415 }], rotate: true }

parser accepts multiple points, they must not interleave

$ app --point 10 20 3.1415 --point 1 2 0.0
Options { point: [Point { point: (), x: 10, y: 20, z: 3.1415 }, Point { point: (), x: 1, y: 2, z: 0.0 }], rotate: false }

--rotate can’t go in the middle of the point definition as the parser expects the second item

$ app --point 10 20 --rotate 3.1415
Error: expected Z, pass --help for usage information

Structure groups

Parsing things like --rect --width W --height H --rect --height H --width W

Combinatoric example

#[derive(Debug, Clone)]
pub struct Options {
    rect: Vec<Rect>,
    mirror: bool,
}

#[derive(Debug, Clone)]
struct Rect {
    rect: (),
    width: usize,
    height: usize,
    painted: bool,
}

fn rect() -> impl Parser<Rect> {
    let rect = long("rect").help("Define a new rectangle").req_flag(());
    let width = short('w')
        .long("width")
        .help("Rectangle width in pixels")
        .argument::<usize>("PX");
    let height = short('h')
        .long("height")
        .help("Rectangle height in pixels")
        .argument::<usize>("PX");
    let painted = short('p')
        .long("painted")
        .help("Should rectangle be filled?")
        .switch();
    construct!(Rect {
        rect,
        width,
        height,
        painted,
    })
    .adjacent()
}

pub fn options() -> OptionParser<Options> {
    let mirror = long("mirror").help("Mirror the image").switch();
    let rect = rect().many();
    construct!(Options { rect, mirror }).to_options()
}

fn main() {
    println!("{:?}", options().run())
}

Derive example

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub struct Options {
    #[bpaf(external, many)]
    rect: Vec<Rect>,
    /// Mirror the image
    mirror: bool,
}

#[derive(Debug, Clone, Bpaf)]
#[bpaf(adjacent)]
struct Rect {
    /// Define a new rectangle
    rect: (),
    #[bpaf(short, long, argument("PX"))]
    /// Rectangle width in pixels
    width: usize,
    #[bpaf(short, long, argument("PX"))]
    /// Rectangle height in pixels
    height: usize,
    #[bpaf(short, long)]
    /// Should rectangle be filled?
    painted: bool,
}

fn main() {
    println!("{:?}", options().run())
}

Output

This example parses multipe rectangles from a command line defined by dimensions and the fact if its filled or not, to make things more interesting - every group of coordinates must be prefixed with --rect

$ app --help

Usage: app [--rect -w=PX -h=PX [-p]]... [--mirror]

Available options:

--rect -w=PX -h=PX [-p]

--rect

Define a new rectangle

-w, --width=PX

Rectangle width in pixels

-h, --height=PX

Rectangle height in pixels

-p, --painted

Should rectangle be filled?

--mirror

Mirror the image

-h, --help

Prints help information

Order of items within the rectangle is not significant and you can have several of them, because fields are still regular arguments - order doesn’t matter for as long as they belong to some rectangle

$ app --rect --width 10 --height 10 --rect --height=10 --width=10
Options { rect: [Rect { rect: (), width: 10, height: 10, painted: false }, Rect { rect: (), width: 10, height: 10, painted: false }], mirror: false }

You can have optional values that belong to the group inside and outer flags in the middle

$ app --rect --width 10 --painted --height 10 --mirror --rect --height 10 --width 10
Options { rect: [Rect { rect: (), width: 10, height: 10, painted: true }, Rect { rect: (), width: 10, height: 10, painted: false }], mirror: true }

But with adjacent they cannot interleave

$ app --rect --rect --width 10 --painted --height 10 --height 10 --width 10
Error: expected --width=PX, pass --help for usage information

Or have items that don’t belong to the group inside them

$ app --rect --width 10 --mirror --painted --height 10 --rect --height 10 --width 10
Error: expected --height=PX, pass --help for usage information

Chaining commands

This example explains adjacent, but the same idea holds. Parsing things like cmd1 --arg1 cmd2 --arg2 --arg3 cmd3 --flag

Combinatoric example

#[derive(Debug, Clone)]
pub struct Options {
    premium: bool,
    commands: Vec<Cmd>,
}

#[derive(Debug, Clone)]
// shape of the variants doesn't really matter, let's use all of them :)
enum Cmd {
    Eat(String),
    Drink { coffee: bool },
    Sleep { time: usize },
}

fn cmd() -> impl Parser<Cmd> {
    let eat = positional::<String>("FOOD")
        .to_options()
        .descr("Performs eating action")
        .command("eat")
        .adjacent()
        .map(Cmd::Eat);

    let coffee = long("coffee")
        .help("Are you going to drink coffee?")
        .switch();
    let drink = construct!(Cmd::Drink { coffee })
        .to_options()
        .descr("Performs drinking action")
        .command("drink")
        .adjacent();

    let time = long("time").argument::<usize>("HOURS");
    let sleep = construct!(Cmd::Sleep { time })
        .to_options()
        .descr("Performs taking a nap action")
        .command("sleep")
        .adjacent();

    construct!([eat, drink, sleep])
}

pub fn options() -> OptionParser<Options> {
    let premium = short('p')
        .long("premium")
        .help("Opt in for premium serivces")
        .switch();
    let commands = cmd().many();
    construct!(Options { premium, commands }).to_options()
}

fn main() {
    println!("{:?}", options().run())
}

Derive example

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub struct Options {
    #[bpaf(short, long)]
    /// Opt in for premium serivces
    pub premium: bool,
    #[bpaf(external(cmd), many)]
    pub commands: Vec<Cmd>,
}

#[derive(Debug, Clone, Bpaf)]
pub enum Cmd {
    #[bpaf(command, adjacent)]
    /// Performs eating action
    Eat(#[bpaf(positional("FOOD"))] String),
    #[bpaf(command, adjacent)]
    /// Performs drinking action
    Drink {
        /// Are you going to drink coffee?
        coffee: bool,
    },
    #[bpaf(command, adjacent)]
    /// Performs taking a nap action
    Sleep {
        #[bpaf(argument("HOURS"))]
        time: usize,
    },
}

fn main() {
    println!("{:?}", options().run())
}

Output

Example implements a parser that supports one of three possible commands:

$ app --help

Usage: app [-p] [COMMAND ...]...

Available options:

-p, --premium

Opt in for premium serivces

-h, --help

Prints help information

Available commands:

eat

Performs eating action

drink

Performs drinking action

sleep

Performs taking a nap action

As usual every command comes with its own help

$ app drink --help

Performs drinking action

Usage: app drink [--coffee]

Available options:

--coffee

Are you going to drink coffee?

-h, --help

Prints help information

Normally you can use one command at a time, but making commands adjacent lets parser to succeed after consuming an adjacent block only and leaving leftovers for the rest of the parser, consuming them as a Vec<Cmd> with many allows to chain multiple items sequentially

$ app eat Fastfood drink --coffee sleep --time=5
Options { premium: false, commands: [Eat("Fastfood"), Drink { coffee: true }, Sleep { time: 5 }] }

The way this works is by running parsers for each command. In the first iteration eat succeeds, it consumes eat fastfood portion and appends its value to the resulting vector. Then second iteration runs on leftovers, in this case it will be drink --coffee sleep --time=5. Here drink succeeds and consumes drink --coffee portion, then sleep parser runs, etc.

You can mix chained commands with regular arguments that belong to the top level parser

$ app sleep --time 10 --premium eat 'Bak Kut Teh' drink
Options { premium: true, commands: [Sleep { time: 10 }, Eat("Bak Kut Teh"), Drink { coffee: false }] }

But not inside the command itself since values consumed by the command are not going to be adjacent

$ app sleep --time 10 eat --premium 'Bak Kut Teh' drink
Error: expected FOOD, pass --help for usage information

Capturing everything between markers

Parsing things like find . --exec foo {} -bar ; --more

Combinatoric example

#[derive(Debug, Clone)]
pub struct Options {
    exec: Option<Vec<OsString>>,
    switch: bool,
}

fn exec() -> impl Parser<Option<Vec<OsString>>> {
    // this defines starting token - "--exec"
    let start = long("exec")
        .help("Spawn a process for each file found")
        .req_flag(());
    // this consumes everything that is not ";"
    let body = any("COMMAND", |s| (s != ";").then_some(s))
        .help("Command and arguments, {} will be replaced with a file name")
        .some("You need to pass some arguments to exec");
    // this defines endint goken - ";"
    let end = literal(";");
    // this consumes everything between starting token and ending token
    construct!(start, body, end)
        // this makes it so everything between those tokens is consumed
        .adjacent()
        // drop the surrounding tokens leaving just the arguments
        .map(|x| x.1)
        // and make it optional so that instead of an empty Vec
        // it is `None` when no `--exec` flags was passed.
        .optional()
}

pub fn options() -> OptionParser<Options> {
    let switch = short('s')
        .long("switch")
        .help("Regular top level switch")
        .switch();
    construct!(Options { exec(), switch }).to_options()
}

fn main() {
    println!("{:?}", options().run())
}

Derive example

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub struct Options {
    #[bpaf(external(execs))]
    exec: Option<Vec<OsString>>,
    #[bpaf(long, short)]
    /// Regular top level switch
    switch: bool,
}

#[derive(Debug, Clone, Bpaf)]
#[bpaf(adjacent)]
struct Exec {
    /// Spawn a process for each file found
    exec: (),

    #[bpaf(
        any("COMMAND", not_semi),
        some("Command and arguments, {} will be replaced with a file name")
    )]
    /// Command and arguments, {} will be replaced with a file name
    body: Vec<OsString>,

    #[bpaf(external(is_semi))]
    end: (),
}

fn not_semi(s: OsString) -> Option<OsString> {
    (s != ";").then_some(s)
}

fn is_semi() -> impl Parser<()> {
    // TODO - support literal in bpaf_derive
    literal(";")
}

// a different alternative would be to put a singular Exec
fn execs() -> impl Parser<Option<Vec<OsString>>> {
    exec().map(|e| e.body).optional()
}

fn main() {
    println!("{:?}", options().run())
}

Output

Generated --help message is somewhat descriptive of the purpose

$ app --help

Usage: app [--exec COMMAND... ;] [-s]

Available options:

--exec COMMAND... ;

--exec

Spawn a process for each file found

COMMAND

Command and arguments, {} will be replaced with a file name

-s, --switch

Regular top level switch

-h, --help

Prints help information

You can have as many items between --exec and ; as you want, they all will be captured inside the exec vector. Extra options can go either before or after the block.

$ app --exec foo --bar ; -s
Options { exec: Some(["foo", "--bar"]), switch: true }

This example uses some to make sure there are some parameters, but that’s optional.

$ app --exec ;
Error: --exec is not expected in this context

Multi-value arguments with optional flags

Parsing things like --foo ARG1 --flag --inner ARG2

So you can parse things while parsing things. Not sure why you might need this, but you can :)

#[derive(Debug, Clone)]
pub struct Options {
    meal: Vec<Meal>,
    premium: bool,
}

#[derive(Debug, Clone)]
struct Meal {
    m: (),
    spicy: Option<usize>,
    drink: bool,
    dish: usize,
}

/// You can mix all sorts of things inside the adjacent group
fn meal() -> impl Parser<Meal> {
    let m = short('o')
        .long("meal")
        .help("A meal [o]rder consists of a main dish with an optional drink")
        .req_flag(());
    let spicy = long("spicy")
        .help("On a scale from 1 to a lot, how spicy do you want your meal?")
        .argument::<usize>("SPICY")
        .optional();
    let drink = long("drink")
        .help("Do you want drink with your meal?")
        .switch();
    let dish = positional::<usize>("DISH").help("Main dish number");
    construct!(Meal {
        m,
        spicy,
        drink,
        dish
    })
    .adjacent()
}

pub fn options() -> OptionParser<Options> {
    let premium = short('p')
        .long("premium")
        .help("Do you want to opt in for premium service?")
        .switch();
    let meal = meal().many();
    construct!(Options { meal, premium }).to_options()
}

fn main() {
    println!("{:?}", options().run())
}

Output

$ app --help

Usage: app [-o [--spicy=SPICY] [--drink] DISH]... [-p]

Available options:

-o [--spicy=SPICY] [--drink] DISH

-o, --meal

A meal [o]rder consists of a main dish with an optional drink

--spicy=SPICY

On a scale from 1 to a lot, how spicy do you want your meal?

--drink

Do you want drink with your meal?

DISH

Main dish number

-p, --premium

Do you want to opt in for premium service?

-h, --help

Prints help information

Let’s start simple - a single flag accepts a bunch of stuff, and eveything is present

$ app --meal 330 --spicy 10 --drink
Options { meal: [Meal { m: (), spicy: Some(10), drink: true, dish: 330 }], premium: false }

You can omit some parts, but also have multiple groups thank to many

$ app --meal 100 --drink --meal 30 --spicy 10 --meal 50
Options { meal: [Meal { m: (), spicy: None, drink: true, dish: 100 }, Meal { m: (), spicy: Some(10), drink: false, dish: 30 }, Meal { m: (), spicy: None, drink: false, dish: 50 }], premium: false }

As usual it can be mixed with standalone flags

$ app --premium --meal 42
Options { meal: [Meal { m: (), spicy: None, drink: false, dish: 42 }], premium: true }

Thanks to many whole meal part is optional

$ app --premium
Options { meal: [], premium: true }

Error messages should be somewhat descriptive

$ app --meal --drink --spicy 500
Error: expected DISH, pass --help for usage information

Performance and other considerations

bpaf can run adjacently restricted parsers multiple times to refine the guesses. It’s best not to have complex inter-fields verification since they might trip up the detection logic: instead of restricting, for example “sum of two fields to be 5 or greater” inside the adjacent parser, you can restrict it outside, once adjacent done the parsing.

There’s also similar method adjacent that allows to restrict argument parser to work only for arguments where both key and a value are in the same shell word: -f=bar or -fbar, but not -f bar.

Trait Implementations

impl<T, P> Parser<T> for ParseCon<P>

where P: Fn(bool, &mut State) -> Result<T, Error>,

fn many(self) -> ParseMany<Self>

where Self: Sized,

Consume zero or more items from a command line and collect them into a Vec

fn collect<C>(self) -> ParseCollect<Self, C, T>

where C: FromIterator<T>, Self: Sized,

Transform parser into a collection parser

fn some(self, message: &'static str) -> ParseSome<Self>

where Self: Sized + Parser<T>,

Consume one or more items from a command line and collect them into a Vec

fn optional(self) -> ParseOptional<Self>

where Self: Sized + Parser<T>,

Turn a required argument into an optional one

fn count(self) -> ParseCount<Self, T>

where Self: Sized + Parser<T>,

Count how many times the inner parser succeeds, and return that number.

fn last(self) -> ParseLast<Self>

where Self: Sized + Parser<T>,

Apply the inner parser as many times as it succeeds, return the last value

fn parse<F, R, E>(self, f: F) -> ParseWith<T, Self, F, E, R>

where Self: Sized + Parser<T>, F: Fn(T) -> Result<R, E>, E: ToString,

Apply a failing transformation to a contained value

fn map<F, R>(self, map: F) -> ParseMap<T, Self, F, R>

where Self: Sized + Parser<T>, F: Fn(T) -> R + 'static,

Apply a pure transformation to a contained value

fn guard<F>(self, check: F, message: &'static str) -> ParseGuard<Self, F>

where Self: Sized + Parser<T>, F: Fn(&T) -> bool,

Validate or fail with a message

fn fallback(self, value: T) -> ParseFallback<Self, T>

where Self: Sized + Parser<T>,

Use this value as default if the value isn’t present on a command line

fn fallback_with<F, E>(self, fallback: F) -> ParseFallbackWith<T, Self, F, E>

where Self: Sized + Parser<T>, F: Fn() -> Result<T, E>, E: ToString,

Use value produced by this function as default if the value isn’t present

fn hide(self) -> ParseHide<Self>

where Self: Sized + Parser<T>,

Ignore this parser during any sort of help generation

fn hide_usage(self) -> ParseUsage<Self>

where Self: Sized + Parser<T>,

Ignore this parser when generating a usage line

fn custom_usage<M>(self, usage: M) -> ParseUsage<Self>

where M: Into<Doc>, Self: Sized + Parser<T>,

Customize how this parser looks like in the usage line

fn group_help<M: Into<Doc>>(self, message: M) -> ParseGroupHelp<Self>

where Self: Sized + Parser<T>,

Attach a help message to a complex parser

fn with_group_help<F>(self, f: F) -> ParseWithGroupHelp<Self, F>

where Self: Sized + Parser<T>, F: Fn(MetaInfo<'_>) -> Doc,

Make a help message for a complex parser from its MetaInfo

fn to_options(self) -> OptionParser<T>

where Self: Sized + Parser<T> + 'static,

Transform Parser into OptionParser to get ready to run it

fn run(self) -> T

where Self: Sized + Parser<T> + 'static,

Finalize and run the parser

fn boxed(self) -> Box<dyn Parser<T>>

where Self: Sized + Parser<T> + 'static,

Create a boxed representation for a parser