Support unit variants when deriving ToCss

This commit is contained in:
Anthony Ramine 2017-06-07 14:53:31 +02:00
parent 7d09ce0495
commit 45e8b0e8c7
14 changed files with 71 additions and 242 deletions

View file

@ -15,9 +15,12 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
}
let style = synstructure::BindStyle::Ref.into();
let match_body = synstructure::each_variant(&input, &style, |bindings, _| {
let match_body = synstructure::each_variant(&input, &style, |bindings, variant| {
if bindings.is_empty() {
panic!("unit variants are not yet supported");
let identifier = to_css_identifier(variant.ident.as_ref());
return Some(quote! {
::std::fmt::Write::write_str(dest, #identifier)
});
}
let (first, rest) = bindings.split_first().expect("unit variants are not yet supported");
where_clause.predicates.push(where_predicate(first.field.ty.clone()));
@ -28,7 +31,7 @@ pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
where_clause.predicates.push(where_predicate(binding.field.ty.clone()));
expr = quote! {
#expr?;
dest.write_str(" ")?;
::std::fmt::Write::write_str(dest, " ")?;
::style_traits::ToCss::to_css(#binding, dest)
};
}
@ -68,3 +71,40 @@ fn where_predicate(ty: syn::Ty) -> syn::WherePredicate {
)],
})
}
/// Transforms "FooBar" to "foo-bar".
///
/// If the first Camel segment is "Moz"" or "Webkit", the result string
/// is prepended with "-".
fn to_css_identifier(mut camel_case: &str) -> String {
let mut first = true;
let mut result = String::with_capacity(camel_case.len());
while let Some(segment) = split_camel_segment(&mut camel_case) {
if first {
match segment {
"Moz" | "Webkit" => first = false,
_ => {},
}
}
if !first {
result.push_str("-");
}
first = false;
result.push_str(&segment.to_lowercase());
}
result
}
/// Given "FooBar", returns "Foo" and sets `camel_case` to "Bar".
fn split_camel_segment<'input>(camel_case: &mut &'input str) -> Option<&'input str> {
let index = match camel_case.chars().next() {
None => return None,
Some(ch) => ch.len_utf8(),
};
let end_position = camel_case[index..]
.find(char::is_uppercase)
.map_or(camel_case.len(), |pos| index + pos);
let result = &camel_case[..end_position];
*camel_case = &camel_case[end_position..];
Some(result)
}