7a72bac779
# Objective Fix #9960 ## Solution Make the `visit` parameter `_visit` if there are no dependencies. New `cargo expand` output: ```rust pub struct Rarity { pub name: SharedStr, pub color: Color, } impl bevy::asset::Asset for Rarity {} impl bevy::asset::VisitAssetDependencies for Rarity { fn visit_dependencies( &self, _visit: &mut impl FnMut(bevy::asset::UntypedAssetId), // <-- fixed ) {} } impl bevy::reflect::TypePath for Rarity { fn type_path() -> &'static str { "myasset::item::Rarity" } fn short_type_path() -> &'static str { "Rarity" } fn type_ident() -> Option<&'static str> { ::core::option::Option::Some("Rarity") } fn crate_name() -> Option<&'static str> { ::core::option::Option::Some( "myasset::item".split(':').next().unwrap(), ) } fn module_path() -> Option<&'static str> { ::core::option::Option::Some("myasset::item") } } ```
84 lines
2.9 KiB
Rust
84 lines
2.9 KiB
Rust
use bevy_macro_utils::BevyManifest;
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use proc_macro::{Span, TokenStream};
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use quote::quote;
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use syn::{parse_macro_input, Data, DeriveInput, Path};
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pub(crate) fn bevy_asset_path() -> syn::Path {
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BevyManifest::default().get_path("bevy_asset")
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}
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const DEPENDENCY_ATTRIBUTE: &str = "dependency";
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#[proc_macro_derive(Asset, attributes(dependency))]
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pub fn derive_asset(input: TokenStream) -> TokenStream {
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let ast = parse_macro_input!(input as DeriveInput);
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let bevy_asset_path: Path = bevy_asset_path();
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let struct_name = &ast.ident;
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let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
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let dependency_visitor = match derive_dependency_visitor_internal(&ast, &bevy_asset_path) {
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Ok(dependency_visitor) => dependency_visitor,
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Err(err) => return err.into_compile_error().into(),
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};
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TokenStream::from(quote! {
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impl #impl_generics #bevy_asset_path::Asset for #struct_name #type_generics #where_clause { }
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#dependency_visitor
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})
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}
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#[proc_macro_derive(VisitAssetDependencies, attributes(dependency))]
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pub fn derive_asset_dependency_visitor(input: TokenStream) -> TokenStream {
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let ast = parse_macro_input!(input as DeriveInput);
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let bevy_asset_path: Path = bevy_asset_path();
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match derive_dependency_visitor_internal(&ast, &bevy_asset_path) {
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Ok(dependency_visitor) => TokenStream::from(dependency_visitor),
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Err(err) => err.into_compile_error().into(),
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}
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}
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fn derive_dependency_visitor_internal(
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ast: &DeriveInput,
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bevy_asset_path: &Path,
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) -> Result<proc_macro2::TokenStream, syn::Error> {
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let mut field_visitors = Vec::new();
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if let Data::Struct(data_struct) = &ast.data {
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for field in &data_struct.fields {
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if field
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.attrs
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.iter()
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.any(|a| a.path().is_ident(DEPENDENCY_ATTRIBUTE))
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{
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if let Some(field_ident) = &field.ident {
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field_visitors.push(quote! {
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#bevy_asset_path::VisitAssetDependencies::visit_dependencies(&self.#field_ident, visit);
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});
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}
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}
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}
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} else {
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return Err(syn::Error::new(
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Span::call_site().into(),
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"Asset derive currently only works on structs",
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));
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}
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let struct_name = &ast.ident;
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let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
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// prevent unused variable warning in case there are no dependencies
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let visit = if field_visitors.is_empty() {
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quote! { _visit }
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} else {
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quote! { visit }
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};
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Ok(quote! {
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impl #impl_generics #bevy_asset_path::VisitAssetDependencies for #struct_name #type_generics #where_clause {
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fn visit_dependencies(&self, #visit: &mut impl FnMut(#bevy_asset_path::UntypedAssetId)) {
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#(#field_visitors)*
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}
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}
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})
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}
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