#![allow(missing_docs)]
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
use bevy_macro_utils::BevyManifest;
use proc_macro::{Span, TokenStream};
use quote::{format_ident, quote};
use syn::{parse_macro_input, Data, DeriveInput, Path};
pub(crate) fn bevy_asset_path() -> Path {
BevyManifest::default().get_path("bevy_asset")
}
const DEPENDENCY_ATTRIBUTE: &str = "dependency";
#[proc_macro_derive(Asset, attributes(dependency))]
pub fn derive_asset(input: TokenStream) -> TokenStream {
let ast = parse_macro_input!(input as DeriveInput);
let bevy_asset_path: Path = bevy_asset_path();
let struct_name = &ast.ident;
let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
let dependency_visitor = match derive_dependency_visitor_internal(&ast, &bevy_asset_path) {
Ok(dependency_visitor) => dependency_visitor,
Err(err) => return err.into_compile_error().into(),
};
TokenStream::from(quote! {
impl #impl_generics #bevy_asset_path::Asset for #struct_name #type_generics #where_clause { }
#dependency_visitor
})
}
#[proc_macro_derive(VisitAssetDependencies, attributes(dependency))]
pub fn derive_asset_dependency_visitor(input: TokenStream) -> TokenStream {
let ast = parse_macro_input!(input as DeriveInput);
let bevy_asset_path: Path = bevy_asset_path();
match derive_dependency_visitor_internal(&ast, &bevy_asset_path) {
Ok(dependency_visitor) => TokenStream::from(dependency_visitor),
Err(err) => err.into_compile_error().into(),
}
}
fn derive_dependency_visitor_internal(
ast: &DeriveInput,
bevy_asset_path: &Path,
) -> Result<proc_macro2::TokenStream, syn::Error> {
let struct_name = &ast.ident;
let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
let visit_dep = |to_read| quote!(#bevy_asset_path::VisitAssetDependencies::visit_dependencies(#to_read, visit););
let is_dep_attribute = |a: &syn::Attribute| a.path().is_ident(DEPENDENCY_ATTRIBUTE);
let field_has_dep = |f: &syn::Field| f.attrs.iter().any(is_dep_attribute);
let body = match &ast.data {
Data::Struct(data_struct) => {
let fields = data_struct.fields.iter();
let field_visitors = fields.enumerate().filter(|(_, f)| field_has_dep(f));
let field_visitors = field_visitors.map(|(i, field)| match &field.ident {
Some(ident) => visit_dep(quote!(&self.#ident)),
None => {
let index = syn::Index::from(i);
visit_dep(quote!(&self.#index))
}
});
Some(quote!( #(#field_visitors)* ))
}
Data::Enum(data_enum) => {
let variant_has_dep = |v: &syn::Variant| v.fields.iter().any(field_has_dep);
let any_case_required = data_enum.variants.iter().any(variant_has_dep);
let cases = data_enum.variants.iter().filter(|v| variant_has_dep(v));
let cases = cases.map(|variant| {
let ident = &variant.ident;
let fields = &variant.fields;
let field_visitors = fields.iter().enumerate().filter(|(_, f)| field_has_dep(f));
let field_visitors = field_visitors.map(|(i, field)| match &field.ident {
Some(ident) => visit_dep(quote!(#ident)),
None => {
let ident = format_ident!("member{i}");
visit_dep(quote!(#ident))
}
});
let fields = match fields {
syn::Fields::Named(fields) => {
let named = fields.named.iter().map(|f| f.ident.as_ref());
quote!({ #(#named,)* .. })
}
syn::Fields::Unnamed(fields) => {
let named = (0..fields.unnamed.len()).map(|i| format_ident!("member{i}"));
quote!( ( #(#named,)* ) )
}
syn::Fields::Unit => unreachable!("Can't pass filter is_dep_attribute"),
};
quote!(Self::#ident #fields => {
#(#field_visitors)*
})
});
any_case_required.then(|| quote!(match self { #(#cases)*, _ => {} }))
}
Data::Union(_) => {
return Err(syn::Error::new(
Span::call_site().into(),
"Asset derive currently doesn't work on unions",
));
}
};
let visit = if body.is_none() {
quote! { _visit }
} else {
quote! { visit }
};
Ok(quote! {
impl #impl_generics #bevy_asset_path::VisitAssetDependencies for #struct_name #type_generics #where_clause {
fn visit_dependencies(&self, #visit: &mut impl FnMut(#bevy_asset_path::UntypedAssetId)) {
#body
}
}
})
}