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//! Define [Leptos](https://leptos.dev/) components using structs.
extern crate proc_macro;
use proc_macro2::TokenStream;
use quote::quote;
use syn::{
AttrStyle, Attribute, Data, DeriveInput, Expr, ExprArray, GenericArgument, Ident, LitBool,
LitStr, Meta, PathArguments, Type, parse_macro_input, spanned::Spanned,
};
#[derive(Debug, Default)]
struct StructComponentAttrArgs {
tag: Option<String>,
dynamic_tag: Option<Vec<(Expr, String)>>,
no_children: Option<bool>,
}
fn parse_struct_component_attr(attr: &Attribute) -> Result<StructComponentAttrArgs, syn::Error> {
if !matches!(attr.style, AttrStyle::Outer) {
Err(syn::Error::new(attr.span(), "not an inner attribute"))
} else if let Meta::List(list) = &attr.meta {
let mut args = StructComponentAttrArgs::default();
list.parse_nested_meta(|meta| {
if meta.path.is_ident("tag") {
let value = meta.value().and_then(|value| value.parse::<LitStr>())?;
args.tag = Some(value.value());
Ok(())
} else if meta.path.is_ident("dynamic_tag") {
let value = meta.value().and_then(|value| value.parse::<ExprArray>())?;
args.dynamic_tag = Some(
value
.elems
.into_iter()
.filter_map(|elem| match &elem {
Expr::Path(path) => path.path.segments.last().map(|segment| {
(elem.clone(), segment.ident.to_string().to_lowercase())
}),
_ => None,
})
.collect(),
);
Ok(())
} else if meta.path.is_ident("no_children") {
let value = meta.value().and_then(|value| value.parse::<LitBool>())?;
args.no_children = Some(value.value());
Ok(())
} else {
Err(meta.error("unknown property"))
}
})?;
Ok(args)
} else {
Err(syn::Error::new(attr.span(), "not a list"))
}
}
#[proc_macro_attribute]
pub fn struct_component(
_attr: proc_macro::TokenStream,
item: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
item
}
#[proc_macro_derive(StructComponent, attributes(struct_component))]
pub fn derive_struct_component(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let derive_input = parse_macro_input!(input as DeriveInput);
let mut args = StructComponentAttrArgs::default();
for attr in &derive_input.attrs {
if attr.path().is_ident("struct_component") {
match parse_struct_component_attr(attr) {
Ok(result) => {
args = result;
}
Err(error) => {
return error.to_compile_error().into();
}
}
}
}
if let Data::Struct(data_struct) = &derive_input.data {
let ident = derive_input.ident.clone();
let mut attributes: Vec<TokenStream> = vec![];
// let mut attribute_checked: Option<TokenStream> = None;
// let mut attribute_value: Option<TokenStream> = None;
let mut listeners: Vec<TokenStream> = vec![];
// let mut attributes_map: Option<TokenStream> = None;
let mut dynamic_tag: Option<(Ident, Vec<(Expr, String)>)> = None;
let mut node_ref: Option<TokenStream> = None;
for field in &data_struct.fields {
if let Some(ident) = &field.ident {
if let Some(attr) = field
.attrs
.iter()
.find(|attr| attr.path().is_ident("struct_component"))
{
match parse_struct_component_attr(attr) {
Ok(args) => {
if let Some(tags) = args.dynamic_tag {
dynamic_tag = Some((ident.clone(), tags));
continue;
}
}
Err(error) => {
return error.to_compile_error().into();
}
}
}
if ident == "attributes" {
// TODO: dynamic attributes
// attributes_map = Some(quote! {
// .chain(
// self.attributes
// .into_iter()
// .flatten()
// .flat_map(|(key, value)| value.map(|value| (
// ::yew::virtual_dom::AttrValue::from(key),
// ::yew::virtual_dom::AttributeOrProperty::Attribute(AttrValue::from(value)),
// )),
// ),
// )
// });
continue;
}
if ident == "node_ref" {
node_ref = Some(quote! {
.node_ref(self.node_ref)
});
continue;
}
if ident.to_string().starts_with("on") {
if let Type::Path(path) = &field.ty {
let event = ident
.to_string()
.strip_prefix("on")
.expect("String should start with `on`.")
.parse::<TokenStream>()
.expect("String should parse as TokenStream.");
let first = path.path.segments.first();
let first_argument = first.and_then(|segment| match &segment.arguments {
PathArguments::None => None,
PathArguments::AngleBracketed(arguments) => {
arguments.args.first().and_then(|arg| match arg {
GenericArgument::Type(Type::Path(path)) => {
path.path.segments.first()
}
_ => None,
})
}
PathArguments::Parenthesized(_) => None,
});
if first.is_some_and(|segment| segment.ident == "Callback") {
listeners.push(quote! {
.on(::leptos::tachys::html::event::#event, move |event| {
self.#ident.run(event);
})
});
continue;
} else if first.is_some_and(|segment| segment.ident == "Option")
&& first_argument.is_some_and(|argument| argument.ident == "Callback")
{
listeners.push(quote! {
.on(::leptos::tachys::html::event::#event, move |event| {
if let Some(listener) = &self.#ident {
listener.run(event);
}
})
});
continue;
}
}
}
match &field.ty {
Type::Path(path) => {
let first = path.path.segments.first();
attributes.push(
if first.is_some_and(|segment| segment.ident == "MaybeProp") {
quote! {
.#ident(move || self.#ident.get())
}
} else {
quote! {
.#ident(self.#ident)
}
},
);
}
_ => {
return syn::Error::new(field.ty.span(), "expected type path")
.to_compile_error()
.into();
}
}
}
}
let arguments = if args.no_children.unwrap_or(false) {
quote! {
self
}
} else {
quote! {
self, children: Option<::leptos::prelude::Children>
}
};
let children = (!args.no_children.unwrap_or(false)).then(|| {
quote! {
.child(children.map(|children| children()))
}
});
let tag_methods = quote! {
// TODO: dynamic attributes
#node_ref
#(#attributes)*
#(#listeners)*
#children
.into_any()
};
if let Some((tag_ident, tags)) = dynamic_tag {
let exprs = tags.iter().map(|(expr, _)| expr).collect::<Vec<_>>();
let tags = tags
.iter()
.map(|(_, tag)| {
let tag = format!("::leptos::html::{tag}()")
.parse::<TokenStream>()
.expect("String should parse as TokenStream.");
quote! {
#tag
#tag_methods
}
})
.collect::<Vec<_>>();
quote! {
impl #ident {
pub fn render(#arguments) -> ::leptos::tachys::view::any_view::AnyView {
match self.#tag_ident {
#(#exprs => #tags,)*
}
}
}
}
.into()
} else if let Some(tag) = args.tag {
let tag = format!("::leptos::html::{tag}()")
.parse::<TokenStream>()
.expect("String should parse as TokenStream.");
quote! {
impl #ident {
pub fn render(#arguments) -> ::leptos::tachys::view::any_view::AnyView {
#tag
#tag_methods
}
}
}
.into()
} else {
return syn::Error::new(derive_input.span(), "`#[struct_component(tag = \"\")] or #[struct_component(dynamic_tag = true)]` is required")
.to_compile_error()
.into();
}
} else {
syn::Error::new(derive_input.span(), "expected struct")
.to_compile_error()
.into()
}
}