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use proc_macro2::TokenStream;
use quote::{format_ident, quote, quote_spanned, IdentFragment};
use syn::{parse_macro_input, Attribute, Data, DeriveInput, ExprPath, Fields, Index};
#[proc_macro_derive(AsyncComponent, attributes(component, state))]
pub fn component_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as DeriveInput);
proc_macro::TokenStream::from(impl_component_stream(&input))
}
fn extract_path_attribute(ident: &str, attrs: &[Attribute]) -> Option<Option<ExprPath>> {
for attr in attrs {
if !attr.path.is_ident(ident) {
continue;
}
let method_path = attr.parse_args::<ExprPath>().ok();
return Some(method_path);
}
None
}
fn impl_component_stream(input: &DeriveInput) -> TokenStream {
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let update_component_body = match input.data {
Data::Struct(ref data) => {
let state_update_call = extract_path_attribute("component", &input.attrs).map(|path| {
quote! {
#path(self);
}
});
let state_poll = update_state_body(&data.fields);
let component_poll = component_update_body(&data.fields);
quote! {
let mut updated = false;
#component_poll
#state_poll
#state_update_call
updated
}
}
Data::Enum(_) => unimplemented!("Derive cannot be applied to enum"),
Data::Union(_) => unimplemented!("Derive cannot be applied to union"),
};
quote! {
impl #impl_generics ::async_component::AsyncComponent for #name #ty_generics #where_clause {
fn update_component(&mut self) -> bool {
#update_component_body
}
}
}
}
fn update_state_body(fields: &Fields) -> TokenStream {
match fields {
Fields::Named(fields) => {
let iter = fields.named.iter().filter_map(|field| {
let method_name = extract_path_attribute("state", &field.attrs)?;
let name = field.ident.as_ref().unwrap();
Some(field_state_update_body(name, method_name))
});
quote! {
#(#iter)*
}
}
Fields::Unnamed(fields) => {
let iter = fields
.unnamed
.iter()
.enumerate()
.filter_map(|(index, field)| {
let method_name = extract_path_attribute("state", &field.attrs)?;
let index = Index::from(index);
Some(field_state_update_body(index, method_name))
});
quote! {
#(#iter)*
}
}
Fields::Unit => {
quote!()
}
}
}
fn field_state_update_body(name: impl IdentFragment, method_name: Option<ExprPath>) -> TokenStream {
let name = format_ident!("{}", name);
let method_call = method_name.map(|path| quote! { #path(self, _recv); });
let update = update_result();
quote_spanned! { name.span() =>
if let Some(_recv) = ::async_component::State::update(&mut self.#name) {
#method_call
#update
}
}
}
fn component_update_body(fields: &Fields) -> TokenStream {
match fields {
Fields::Named(fields) => {
let iter = fields.named.iter().filter_map(|field| {
let method_name = extract_path_attribute("component", &field.attrs)?;
let name = field.ident.as_ref().unwrap();
Some(field_component_update_body(name, method_name))
});
quote! {
#(#iter)*
}
}
Fields::Unnamed(fields) => {
let iter = fields
.unnamed
.iter()
.enumerate()
.filter_map(|(index, field)| {
let method_name = extract_path_attribute("component", &field.attrs)?;
let index = Index::from(index);
Some(field_component_update_body(index, method_name))
});
quote! {
#(#iter)*
}
}
Fields::Unit => {
quote!()
}
}
}
fn field_component_update_body(
name: impl IdentFragment,
method_name: Option<ExprPath>,
) -> TokenStream {
let name = format_ident!("{}", name);
let method_call = method_name.map(|path| quote! { #path(self); });
let update = update_result();
quote_spanned! { name.span() =>
if ::async_component::AsyncComponent::update_component(&mut self.#name) {
#update
}
#method_call
}
}
fn update_result() -> TokenStream {
quote! {
if !updated {
updated = true
}
}
}