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templater: add generic wrappers for Option<TemplateProperty>

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Option<P> allows us to embed optional argument property in tuple.

    let maybe_arg = maybe_pair.map(|pair| parse(...))?;
    chain_properties((self, maybe_arg), |_: &(Context, Option<_>)| ...)

For one optional argument, we can instead switch the property functions:

    if let Some(pair) = maybe_pair {
        let arg = pair.map(|pair| parse(...))?;
        chain_properties((self, arg), |_: &(Context, _)| ...)
    } else {
        chain_properties(self, |_: &Context| ...)
    }

If we have various combinations of optional arguments, using Option<P> would
be better.
This commit is contained in:
Yuya Nishihara 2023-02-05 19:35:34 +09:00
parent 13d9dc4460
commit 097d3a0e6c
1 changed files with 8 additions and 0 deletions
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8
src/templater.rs
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@ -210,6 +210,14 @@ impl<C, P: TemplateProperty<C> + ?Sized> TemplateProperty<C> for Box<P> {
}
}
impl<C, P: TemplateProperty<C>> TemplateProperty<C> for Option<P> {
type Output = Option<P::Output>;
fn extract(&self, context: &C) -> Self::Output {
self.as_ref().map(|property| property.extract(context))
}
}
// Implement TemplateProperty for tuples
macro_rules! tuple_impls {
($( ( $($n:tt $T:ident),+ ) )+) => {