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//! Helper types and macros for creating custom functions.
use crate::syntax::{ParseContext, Parsed};
use crate::syntax::func::FuncHeader;
use crate::syntax::span::Spanned;
pub mod prelude {
pub use crate::layout::prelude::*;
pub use crate::layout::{LayoutContext, Commands, layout};
pub use crate::layout::Command::{self, *};
pub use crate::style::{LayoutStyle, PageStyle, TextStyle};
pub use crate::syntax::SyntaxModel;
pub use crate::syntax::expr::*;
pub use crate::syntax::func::*;
pub use crate::syntax::func::keys::*;
pub use crate::syntax::func::values::*;
pub use crate::syntax::span::{Span, Spanned};
}
/// Parse a function from source code.
pub trait ParseFunc {
type Meta: Clone;
/// Parse the header and body into this function given a context.
fn parse(
header: FuncHeader,
body: Option<Spanned<&str>>,
ctx: ParseContext,
metadata: Self::Meta,
) -> Parsed<Self> where Self: Sized;
}
#[macro_export]
macro_rules! function {
// Entry point.
($(#[$outer:meta])* $v:vis $storage:ident $name:ident $($r:tt)*) => {
function!(@def($name) $(#[$outer])* $v $storage $name $($r)*);
};
(@def($name:ident) $definition:item $($r:tt)*) => {
$definition
function!(@meta($name) $($r)*);
};
// Metadata.
(@meta($name:ident) type Meta = $meta:ty; $($r:tt)*) => {
function!(@parse($name, $meta) $($r)*);
};
(@meta($name:ident) $($r:tt)*) => {
function!(@parse($name, ()) $($r)*);
};
// Parse trait.
(@parse($($a:tt)*) parse(default) $($r:tt)*) => {
function!(@parse($($a)*) parse(_h, _b, _c, _e, _d, _m) {Default::default() } $($r)*);
};
(@parse($($a:tt)*) parse($h:ident, $b:ident, $c:ident, $e:ident, $d:ident) $($r:tt)* ) => {
function!(@parse($($a)*) parse($h, $b, $c, $e, $d, _metadata) $($r)*);
};
(@parse($name:ident, $meta:ty) parse(
$header:ident,
$body:ident,
$ctx:ident,
$errors:ident,
$decos:ident,
$metadata:ident
) $code:block $($r:tt)*) => {
impl $crate::func::ParseFunc for $name {
type Meta = $meta;
fn parse(
#[allow(unused)] mut header: $crate::syntax::func::FuncHeader,
#[allow(unused)] $body: Option<$crate::syntax::span::Spanned<&str>>,
#[allow(unused)] $ctx: $crate::syntax::ParseContext,
#[allow(unused)] $metadata: Self::Meta,
) -> $crate::syntax::Parsed<Self> where Self: Sized {
let mut errors = vec![];
let mut decorations = vec![];
#[allow(unused)] let $header = &mut header;
#[allow(unused)] let $errors = &mut errors;
#[allow(unused)] let $decos = &mut decorations;
let output = $code;
for arg in header.args.into_iter() {
errors.push(err!(arg.span(); "unexpected argument"));
}
$crate::syntax::Parsed { output, errors, decorations }
}
}
function!(@layout($name) $($r)*);
};
(@layout($name:ident) layout($this:ident, $ctx:ident, $errors:ident) $code:block) => {
impl $crate::syntax::Model for $name {
fn layout<'a, 'b, 'c, 't>(
#[allow(unused)] &'a $this,
#[allow(unused)] mut $ctx: $crate::layout::LayoutContext<'b, 'c>,
) -> $crate::layout::DynFuture<'t, $crate::layout::Layouted<
$crate::layout::Commands<'a>>
> where
'a: 't,
'b: 't,
'c: 't,
Self: 't,
{
Box::pin(async move {
let mut errors = vec![];
#[allow(unused)] let $errors = &mut errors;
let output = $code;
$crate::layout::Layouted { output, errors }
})
}
}
};
}
/// Parse the body of a function.
///
/// - If the function does not expect a body, use `parse!(nope: body, errors)`.
/// - If the function can have a body, use `parse!(opt: body, ctx, errors, decos)`.
#[macro_export]
macro_rules! body {
(opt: $body:expr, $ctx:expr, $errors:expr, $decos:expr) => ({
$body.map(|body| {
// Since the body span starts at the opening bracket of the body, we
// need to add 1 column to find out the start position of body
// content.
let start = body.span.start + $crate::syntax::span::Position::new(0, 1);
let parsed = $crate::syntax::parse(start, body.v, $ctx);
$errors.extend(parsed.errors);
$decos.extend(parsed.decorations);
parsed.output
})
});
(nope: $body:expr, $errors:expr) => {
if let Some(body) = $body {
$errors.push($crate::err!(body.span; "unexpected body"));
}
};
}
/// Construct an error with optional severity and span.
///
/// # Examples
/// ```
/// err!(span; "the wrong {}", value);
/// err!(@Warning: span; "non-fatal!");
/// err!("no spans here ...");
/// ```
#[macro_export]
macro_rules! err {
(@$severity:ident: $span:expr; $($args:tt)*) => {
$crate::syntax::span::Spanned { v: err!(@Error: $($args)*), span: $span }
};
(@$severity:ident: $($args:tt)*) => {
$crate::error::Error {
message: format!($($args)*),
severity: $crate::error::Severity::$severity,
}
};
($($tts:tt)*) => { err!(@Error: $($tts)*) };
}
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