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Simplify machinery to serialise optional parts of CSS values

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We simply implement ToCss for Option<T>, printing nothing if the value is None,
and we then use SequenceWriter to skip writing of separators around empty parts.
This commit is contained in:
Anthony Ramine 2017-06-21 10:15:31 +02:00
parent cedd5222d2
commit 39e29f557e
8 changed files with 152 additions and 131 deletions
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24
components/style_derive/to_css.rs
View file

@ -17,24 +17,22 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
let style = synstructure::BindStyle::Ref.into();
let match_body = synstructure::each_variant(&input, &style, |bindings, variant| {
let mut identifier = to_css_identifier(variant.ident.as_ref());
let mut expr = if let Some((first, rest)) = bindings.split_first() {
if has_free_params(&first.field.ty, &input.generics.ty_params) {
where_clause.predicates.push(where_predicate(first.field.ty.clone()));
}
let mut expr = quote! {
::style_traits::ToCss::to_css(#first, dest)
};
for binding in rest {
let mut expr = if !bindings.is_empty() {
let mut expr = quote! {};
for binding in bindings {
if has_free_params(&binding.field.ty, &input.generics.ty_params) {
where_clause.predicates.push(where_predicate(binding.field.ty.clone()));
}
expr = quote! {
#expr?;
::std::fmt::Write::write_str(dest, " ")?;
::style_traits::ToCss::to_css(#binding, dest)
#expr
writer.item(#binding)?;
};
}
expr
quote! {{
let mut writer = ::style_traits::values::SequenceWriter::new(&mut *dest, " ");
#expr
Ok(())
}}
} else {
quote! {
::std::fmt::Write::write_str(dest, #identifier)
@ -80,7 +78,7 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
quote! {
impl #impl_generics ::style_traits::ToCss for #name #ty_generics #where_clause {
#[allow(unused_variables, unused_imports)]
#[allow(unused_variables)]
#[inline]
fn to_css<W>(&self, dest: &mut W) -> ::std::fmt::Result
where